buildings

Article Deploying Geometric Dimensioning and Tolerancing in Construction

Saeed Talebi 1,* , Lauri Koskela 1 , Patricia Tzortzopoulos 1 , Michail Kagioglou 2 and Alex Krulikowski 3

1 Innovative Design Lab, School of Art, Design and Architecture, University of Huddersfield, HD1 3DH Huddersfield, UK; [email protected] (L.K.); [email protected] (P.T.) 2 School of Engineering, Western Sydney University, NSW 2751 Sydney, Australia; [email protected] 3 Krulikowski Consulting LLC, Bradenton, FL 34202, USA; [email protected] * Correspondence: [email protected]



Received: 31 December 2019; Accepted: 24 March 2020; Published: 26 March 2020


Abstract: No standardised approach appears to exist in the architecture, engineering, and construction (AEC) industry for the communication of tolerance information on drawings. As a result of this shortcoming, defects associated with dimensional and geometric variability occur with potentially severe consequences. In contrast, in mechanical engineering, geometric dimensioning and tolerancing (GD&T) is a symbolic language widely used to communicate both the perfect geometry and the tolerances of components and assemblies. This paper prescribes the application of GD&T in construction with the goal of developing a common language called geometric dimensioning and tolerancing in construction (GD&TIC) to facilitate the communication of tolerance information throughout design and construction. design science research is the adopted methodological approach. Evidence was collated from direct observations in two construction projects and two group interviews. A focus group meeting was conducted to evaluate whether the developed solution (GD&TIC) fulfilled its aim. The contribution of this paper to designers, to organisations involved in developing AEC industry standards, and to the scholarly community is twofold: (1) It is an attempt to develop a standardised approach (GD&TIC) for the communication of tolerance information in AEC, and (2) it identifies discrepancies between GD&TIC rules and some of the commonly used American and British standards on tolerances.

Keywords: dimensional tolerance management; communication of tolerance information in construction; tolerance-related defects; tolerancing in architecture and engineering; tolerance requirement; tolerance specification; tolerance analysis; geometric variation; construction tolerances; tolerance risk; geometric dimensioning and tolerancing; building movement; building information modelling; tolerance compliance control

1. Introduction Materials and components cannot be exactly dimensioned and positioned in the way that they were designed. Tolerances are defined as the accepted amount of variations of materials and components from nominal values or design specifications [1]. There are two types of tolerances: (1) dimensional tolerances, stating the permitted amount of deviation for a specific size, e.g., floor thickness; and (2) geometric tolerances, stating the allowed amount of deviation on a specific geometric property, e.g., the flatness of concrete slabs [2]. Construction projects are traditionally made up of an assembly of several different factory-made components and components produced in situ. Construction tolerances range from less than a millimetre for many factory-made components to several millimetres for many

Buildings 2020, 10, 62; doi:10.3390/buildings10040062 www.mdpi.com/journal/buildings Buildings 2020, 10, 62 2 of 29 in-situ components [3]. Moreover, contemporary buildings have become lighter and more vulnerable to building movement and subsequent geometric changes [4]. The lack of uniformity of accuracy between factory-made and in-situ components, as well as the higher level of building movements in contemporary buildings are two major factors that affect the dimensional and geometric accuracy of buildings [5]. The conversion of a good design into a good product (e.g., a building) is a matter of keeping dimensional and geometric variations within tolerances that are predetermined at the design stage [6]. The acceptability of a product depends on whether its variations in size and geometry fall within set limits; thus, the bridge between design and production is tolerance. In other words, tolerances interlink design with construction because, without specifying the tolerances, it is not clear whether components and sub-assemblies (i.e., connections of two or more components) meet the design intent regarding the accuracy of the final product. The exchange of tolerance information between design and construction teams is essential to ensure that components fit and function properly [7]. However, when designers are developing ideal assemblies of components within their drawings and models, they tend to presume that these components will fit together perfectly and they often do not take tolerances in to consideration [8]. One reason for this is that no standardised form of information exchange, particularly concerning tolerances, exists in construction design documents (e.g., drawings) [9]. In other words, design documents do not adequately include tolerance information and therefore do not transfer presumed tolerance information between parties involved in project delivery because of the lack of a tolerancing system (i.e., a system to communicate the tolerance information) in architecture, engineering, and construction (AEC). In this paper, tolerance information represents the permitted dimensional and geometric variations of a component or sub-assembly to ensure that functional requirements (e.g., water tightness, safety, serviceability, durability, constructability, the fit between components, structural stability, aesthetics, and energy performance) are satisfied [10]. The improvement of tolerancing is expected to reduce defects associated with dimensional and geometric variability, referred to hereafter as tolerance problems [11]; however, the existing literature do not offer any considerable actionable advice to improve tolerancing. As a result of shortcomings in interlinking design with construction through tolerancing, tolerance problems occur [4]. Tolerance problems may adversely impact functional requirements, considerably increase the cost of construction and maintenance [12], cause delays [13], and increase material wastage [14]. Those problems influence customer satisfaction and are often at the centre of disputes between consumer, contractor, supply chain, and client [15,16]. Hence, there is a clear need in construction to develop a tolerancing system when compiling design documents. The system of geometric dimensioning and tolerancing (GD&T) is widely used in mechanical engineering as a common language to facilitate the communication of tolerance information [17]. GD&T is successful in significantly reducing tolerance problems in manufacturing [18] and reducing the number of ambiguous situations that arise when using conventional tolerancing approaches [19]. Though the potential application of GD&T in the AEC industry has been acknowledged before [20], it has not yet been thoroughly investigated. The aim of this paper is to prescribe a new tolerancing system for AEC drawings by applying GD&T in construction, termed GD&TIC. GD&TIC is expected to improve the communication of tolerance information and reduce tolerance problems that occur due to the lack of a tolerancing system in the AEC industry. Unlike previous studies that have considered GD&T for tolerance analysis (i.e., the calculation of combined variations), this research applies GD&T in construction to improve the communication of tolerance information. GD&TIC communicate dimensional and geometric variations through a set of systematic rules and consistent terminology, as opposed to conventional tolerancing systems that only communicate dimensional tolerances [21]. In this research paper, first, the related background is presented. The research method used for this research is explained. The proposed tolerancing system, GD&TIC, is then introduced, and the application of GD&TIC is delineated through examples. The discrepancies between the proposed system and some of the existing reference Buildings 2020, 10, x FOR PEER REVIEW 3 of 33

BuildingsGD&TIC2020 is, delineated10, 62 through examples. The discrepancies between the proposed system and some3 of 29 of the existing reference documents (i.e., standards, industry guidance bulletins, and codes of practice) are then investigated in order to identify incompatibilities between the proposed tolerancing documents (i.e., standards, industry guidance bulletins, and codes of practice) are then investigated in system and existing reference documents. Given that numerous reference documents addressing order to identify incompatibilities between the proposed tolerancing system and existing reference tolerances exist, the scope of the research reported in this paper includes the investigation of documents. Given that numerous reference documents addressing tolerances exist, the scope of the discrepancies between GD&TIC and American and British reference documents. The proposed research reported in this paper includes the investigation of discrepancies between GD&TIC and tolerancing system is evaluated. The findings and contributions to knowledge are discussed. American and British reference documents. The proposed tolerancing system is evaluated. The Eventually, conclusions drawn from the research, and suggestions for follow-on research are findings and contributions to knowledge are discussed. Eventually, conclusions drawn from the discussed. research, and suggestions for follow-on research are discussed. 2. Theoretical Background 2. Theoretical Background

2.1. Tolerancing in Construction The ineineffectiveffective communication of tolerance information is a perennial challenge in the AEC industry, andand insuinsufficientfficient attentionattention hashas beenbeen devoteddevoted toto tolerancingtolerancing [[8,22].8,22]. Architects and engineers typically do not specify tolerances in their drawingsdrawings and use chain dimensioning, in which all dimensions are connected head-to-tail asas chains withoutwithout anyany tolerance [[23].23]. It is known that tolerance problems mainlymainly occur occur in thein connectionsthe connections between betw theeen structural the structural frame and frame non-structural and non-structural components (e.g.,components cladding, (e.g., panelling cladding, units, panelling pipework, units, lift wells, pipework, and stairwells) lift wells, [6 ].and Designers stairwells) sometimes [6]. Designers use the termsometimes ‘HOLD’ use or the the term plus ‘HOLD’/minus sign or the ( ),plus/minus as a prefix sign or su (±),ffix as to a distinguish prefix or suffix between to distinguish important between and less ± important dimensionsand less important in connections dimensions between in structural connections and non-structural between structural components and non-structural [24]. However, thecomponents exact amount [24]. ofHowever, permitted the variations exact amount is not of stated permitted or communicated variations is innot either stated of or these communicated approaches. in eitherTolerances of these can approaches. be communicated on drawings by using the conventional plus/minus system [25,26]. FigureTolerances1 illustrates can anbe examplecommunicated of the on application drawings of by the using conventional the conventional plus /minus plus/minus system system for a square[25,26]. holeFigure [5 ].1 illustrates The conventional an example system of the results application in simplicity of the conventional in the communication plus/minus of system tolerance for informationa square hole [ 27[5].]. The However, conventional this system system appearsresults in to simplicity not distinguish in the communication between different of tolerance types of dimensionalinformation [27]. and geometricHowever, tolerancesthis system (e.g., appears flatness, to plumbness,not distinguish and clearance)between different [28]. As types a result, of designersdimensional and and construction geometric teamstolerances in the (e.g., industry flatness, cannot plumbness, become systematicallyand clearance) aware[28]. As of dia ffresult,erent typesdesigners of tolerances and construction and lack theteams vocabulary in the industry to communicate cannot become tolerance systematically information aware [5,24]. of different types of tolerances and lack the vocabulary to communicate tolerance information [5,24].

Figure 1. Example of the communication of tolerance information for a hole at a fascia joint using the conventional plusplus/minus/minus system [[5]5]. The terminology for the communication of tolerance information in AEC is mainly defined by The terminology for the communication of tolerance information in AEC is mainly defined by reference documents [24]. The terminology is currently inconsistent and fragmented across various reference documents [24]. The terminology is currently inconsistent and fragmented across various reference documents [29]. This is because most of the existing reference documents are considerably out reference documents [29]. This is because most of the existing reference documents are considerably of date and have been developed by different independent organisations [30], and no thorough attempt out of date and have been developed by different independent organisations [30], and no thorough has been made to harmonise the terminology [31]. For example, [32,33] use the term ‘verticality’, while [15,34] use the term ‘plumbness’; [35,36] use the term ‘alignment’, while [15,36,37] uses the term ‘parallelism’. Such discrepancies in terminology are confusing for researchers and practitioners, and, Buildings 2020, 10, 62 4 of 29 therefore, there has been a call to revise American and British reference documents addressing the communication of tolerance information [38]. It will be hard to introduce a completely new terminology on a worldwide basis even if it has enough expressiveness [39]. Rather, the terminology used in the existing reference documents should be considered as a basis, and any discrepancy between new developments and existing terminology should be investigated and refined to avoid incompatible developments that would cause even further confusion [40]. Since its establishment, building information modelling (BIM) has been expected to significantly improve the communication of tolerance information [41]. In particular, unlike previous Computer Aided Design (CAD) systems, BIM does not represent objects with fixed geometry. Rather, parametric modelling in BIM allows components to receive attributes such as tolerance information that determines the geometry of components [42]. Nevertheless, the communication of tolerance information in BIM is still limited to the conventional plus/minus approach for a single or group of similar components [43]. Despite the fact that customised tolerance annotations can be created, it appears that no standard tolerancing approach exists for the communication of tolerance information in BIM [44]. All in all, the current practice of architects and engineers regarding tolerancing, the terminology and tolerancing methods used in existing reference documents, and the current functions of BIM for tolerancing often establish an ambiguous and incomplete communication of tolerance information on drawings and models [19], which can result in tolerance problems [9].

2.2. Geometric Dimensioning and Tolerancing GD&T was first developed during World War II and became part of the military standards [45]. It is a symbolic language [17] that communicates both the perfect geometry and tolerances for a component [46]. It specifies the permitted variation in size, form, orientation, and location of features (e.g., size or surface) on a component [28]. It also conveys the design intent regarding dimensions and tolerances, not only by defining the size and shape of the component but also by representing the relationship between components in an assembly [47]. The objective of this tolerancing system is to ensure that tolerances are established based on the functional requirements so that the components in an assembly will function as intended [46]. It should be emphasised that, in manufacturing, there is currently no other method than GD&T by which a component can be defined in the design without ambiguity [48]. Ignoring GD&T results in the acceptance of parts based on specifications that then fail to function [17], or the rejection of parts that are out of specification that still function properly [49].

2.3. Previous Application of Geometric Dimensioning and Tolerancing in the AEC Industry After reviewing the literature, it was found that there has been an attempt to adopt GD&T in the AEC industry. An analytical method called tolerance mapping has been proposed to evaluate interrelationships between components while considering their geometric categories [20]. Though GD&T principles are used in this method, this research is concerned with using GD&T for the tolerance analysis (i.e., the calculation of combined variations) of a given design, rather than for the communication of tolerance information [4,50]. The use of GD&T in this research is not going into detail about how tolerance information for various components can be communicated using GD&T. In other words, the geometric characteristic symbols of GD&T have not been used to communicate the tolerance information thus far; rather, they have been used for performing the tolerance analysis [13].

3. Research Method This research adopted the design science research (DSR) methodological approach. DSR focuses on designing an artefact and prescribing a solution to solve a problem in practice while also contributing to theory [51–53]. In other words, the key tasks of DSR are (1) to prescribe an artefact that will address the practical problems by its developed applicable solutions [54] and (2) to bring together the two realities of practice and theory [52]. This approach was originally developed in the area of information systems, but a number of authors, such as [55–58], have suggested that DSR should be used to develop Buildings 2020, 10, 62 5 of 29 solutions for solving practical and relevant problems in AEC. DSR is about prescribing and evaluating, which means designing and constructing an artefact and then ensuring that the identified problem has been solved [59]. The artefacts are created with the ultimate goal of solving problems, making changes in the application area, and improving performance [60]. The outcome of DSR, the artefact, has a prescriptive nature as it aims at solving a practical problem [61]. The focus of this research was not only on understanding and describing the problem but also on solving a practical problem and constructing a new artefact that can improve the existing practice of the AEC industry in terms of tolerancing. The proposed artefact of this research was GD&TIC. As discussed in Section 2.1, there is a need for further research in tolerancing from both theoretical and practical viewpoints. From a theoretical viewpoint, the literature has mostly focused on exploring the problem with communicating tolerance information rather than on proposing a solution to improve tolerancing; it therefore gives limited practical recommendations [25,62,63]. From a practical viewpoint, there is evidence that the lack of a standardised approach for tolerancing leads to ambiguous situations during design and tolerance problems during construction [4,5,9]. Therefore, DSR seemed appropriate for this research. The following steps were taken in this research to undertake DSR [53,59,64–66]: (1) problem definition, (2) awareness of problem, (3) the development of solution, and (4) evaluation. The steps taken to undertake this research are presented in the ensuing sections.

3.1. Step One: Problem Definition ‘Problem definition’ is suggested as a first step for the development of an artefact [59,64–66]. The identified problem should have potential for research and should be relevant to practice [64,67]. In this step, a review of the literature was carried out not only in AEC but also in mechanical engineering and manufacturing to characterise the terms ‘tolerancing’ and ‘communication of tolerance information’, as well as to recognise the areas of concern for tolerancing in AEC from the earlier researchers’ point of view. The literature helped the authors to understand the underlying needs of the AEC industry in terms of tolerancing and the potential solution in manufacturing (GD&T). A summary of the findings of this step are presented in Section 2.1.

3.2. Step Two: Problem Awareness The next step is ‘problem awareness’, which can arise from multiple sources including empirical studies [59,64,65]. This step in the research included exploratory empirical studies in two construction projects (i.e., case A and case B). The empirical studies were aimed at identifying tolerance problems that occurred as a result of the poor communication of tolerance information and then thoroughly understanding the reason behind their occurrence. Despite the potentially severe magnitude and impact of such tolerance problems, it appears that there is little documentation and analysis of tolerance problems that have occurred due to the lack of a tolerancing system in the construction literature [68]. Therefore, the empirical studies were essential to establish problem awareness. Those tolerance problems then were used as a basis to delineate the application of GD&TIC through relevant examples in Section 4.1. Details of the projects studied and the development stages of these projects are given in Table1.

Table 1. Type of projects studied and their stage of development.

Project Type of Project Development Stage The installation of the building Case A A circa 7500 m2 building envelope and interior components A circa 2.30 ha terraced Case B Erection of structural frame warehouse/manufacturing building Buildings 2020, 10, 62 6 of 29

A non-probability sampling (non-random sampling), based on the authors’ subjective judgement, was used in this study to select cases. Among the non-probability sampling techniques (quota, purposive, snowball, self-selected, and convenience) [69], purposive sampling, which highlights the importance of conscious decision-making, was adopted. This form of sampling is used when working with a very small sample, such as in case study research and when the researcher intends to select cases that are particularly informative [70]. The purposive sample of this study was based on the following criteria: (1) the acknowledgment of the need for a better tolerancing system by the main contractors executing the projects, (2) the willingness to give the authors access to construction sites, and (3) the stage of development. Regarding the latter criterion, tolerance problems in the connection between the structural frame and other components could be identified during empirical studies. Such problems are amongst the most recurring and costly tolerance problems, as mentioned in Section 2.1. This implies that the selected cases were informative due to the type of tolerance problems identified. The observations of two cases led to the satisfactory achievement of theoretical saturation [71] because it resulted in a deep understanding of how the lack of a tolerancing system leads to tolerance problems on site and provided an adequate basis to the application of GD&TIC through relevant examples in Section 4.1. While two cases may appear to be a small sample, the sample size in qualitative research is directly linked to the quality of data in supporting the aim of the study. In other words, the purposive sampling in this study ensured that right cases were selected and theoretical saturation, which is more important than the size of sample [72], was achieved. Data collection tools used included direct observations and two group interviews. Direct observations in this research were carried out to identify tolerance problems that occurred as a result of the poor communication of tolerance problems. The tolerance problems identified through observations were validated in two group interviews, one for Case A and one for Case B. In other words, the group interviews were used for the refinement of the description of the tolerance problems and the reason behind their occurrence. The multiple data collection methods resulted in triangulation that contributed to the rigour of the research [73]. In direct observations, the researcher does not become an internal member of the case being investigated [74] and only observes activities in the field [74]. The observations in Case A and Case B took ten and five months, respectively. The list of participants in each group interview is given in Table2. The interviewees were suggested by the managing directors of the main contractors because they were engaged with the project from the beginning and were fully aware of all issues on site including tolerance problems. This ensured that the right participants were on board, which is more important than the number of those participants [72]. The participants were asked whether the tolerance problems and the reason behind their occurrence had been presented adequately. The participants confirmed that the main cause of the occurrence of the identified tolerance problems was due to the poor communication of dimensional and geometric variations between designers and construction trades.

Table 2. Role/position of interviewees in Case A and Case B.

Case A Case B Role/position of interviewee Role/position of interviewee Project Director Design Manager Project Director Architect Senior Project Manager Site Engineer Site Manager Quantity Surveyor Site Engineer Senior Quantity Surveyor

The list of tolerance problems identified in Case A and Case B are presented in Table3. Further details of those tolerance problems can be found in Table A1. After the completion of the literature Buildings 2020, 10, 62 7 of 29 review in step one and the empirical studies in step two, the importance and relevance of the research problem (i.e., the lack of a standardised tolerancing system) could be ascertained by the authors.

Table 3. Summary the tolerance problems identified in Cases A and B.

Project Corresponding No. Description Case A Tolerance Problem 1 Flatness of concrete slabs Case A Tolerance Problem 2 Perpendicularity of columns and cladding stone panels Case A Tolerance Problem 3 Straightness of beams Case B Tolerance Problem 4 Parallelism of doorways Case B Tolerance Problem 5 Position of purlins on the roof Case B Tolerance Problem 6 Position of columns

3.3. Step Three: Development The ‘development’ step, for which creativity was an inevitable part, was then undertaken [59,64–66]. In this step, the proposed artefact (GD&TIC) was developed (prescribed) based upon the findings from Step One and Step Two. In Step One, the review of the conventional methods for tolerancing in AEC and methods for tolerancing in manufacturing helped the authors to understand the shortcomings of the conventional methods for the tolerancing in AEC and to identify GD&T as a solution to improve the tolerancing in AEC. In Step Two, the analysis of the identified tolerance problems helped to gain an understanding of how the lack of a tolerancing system in AEC leads to tolerance problems on site. In Step Three, the proposed solution was developed based on the configuration of the gained understanding from the literature review on GD&T and analysis of the characteristics of tolerance problems that occurred due to the lack of a tolerancing system. The application of GD&TIC was delineated in Step Three through relevant examples found in Step Two. Moreover, an analysis of the discrepancies between the existing reference documents and GD&TIC’s rules in Step Three helped to ensure the compatibility of GD&TIC with existing reference documents and avoid developing incompatible solutions with those reference documents. In Step Three, it was prescribed that how GD&T’s rules should be applied in the AEC industry. More specifically, this research proposed (1) a definition for the tolerance zone in AEC, (2) how a tolerance zone should be applied to construction component, (3) what characteristic symbols are more applicable in AEC, (4) how components should be controlled by each geometric characteristic in GD&TIC, and (5) how GD&TIC symbols should be inserted into drawings. The results of this step are presented in Section 4.1.

3.4. Step Four: Evaluation ‘Evaluation’ is the final DSR step [59,64–66]. Attention has been drawn to the focus group as a method for evaluating the utility of artefacts developed through DSR [75], and this method was used in this research. The principles of the unique adequacy (UA) requirement of methods was used to ensure the thorough evaluation in this research [76]. This approach is the most fundamental principle of ‘ethnomethodological research’, for which the focus is on a detailed study of directly observable practices performed by members of a local setting [77]. The action in this research was ‘tolerancing’, and the local setting was the ‘AEC industry’. The UA requirement of method has two related criteria: the weak and strong forms [78]. In its weak form, the UA requirements demands to analyse the AEC industry setting adequately in a way that the researcher gains the competence about what any member in that setting would ordinary know about a particular practice [76]. This competence is referred to as ‘knowing how’; it consists of being able to perform relevant activities within that setting [79]. The weak requirement demands the researcher to become vulgarly competent in a more specialised practice [80]. In this research, the observations and group interviews in Case A and B helped the authors to gain the competence in tolerancing. The researcher then needs to develop a practical artefact that an outsider cannot develop without having the competence [81]. The practical artefact in this research was the GD&TIC. Buildings 2020, 10, 62 8 of 29

The strong requirement demands the methods of analysis used to report on a setting to be derived from that setting [79]. This stipulates the application of a policy of ‘ethnomethodological indifference’, i.e., it refuses to evaluate the activities that constitute the setting by approaches that are not part of that setting [81]. In other words, the participants invited to the focus group must be the same as the participants attended the group interview by which the competency about tolerancing was achieved. As a result, the participants, who (1) are aware of the problem, (2) contributed to develop the artefact, and (3) would be the potential users of the artefact, are in fact confirming the final solution [82]. Note that potential users of the artefact are the main source of knowledge because they can adequately inform the evaluation of the artefact [61]. If a new participant group were approached for the evaluation, the level of understanding of the new participants from the proposed solution would have been by far lower, and the authors recognise the effort that would have had to place in order to explain the problem and introduce the solution [75]. In the focus group, the identified tolerance problems were reviewed, and then it was explained to the participants how those problems could have been avoided using GD&TIC. Overall and generally, as a result of complying with the weak and strong criteria, a realistic environment, in which the artefact is implemented, will be approximated [83], and this makes the focus group as strong as the implementation [82]. The evaluation should be based on appropriate criteria [54]. The criteria proposed by [54,84–86] were used to develop a framework to evaluate the solution developed in this research (Table4). The framework has three hierarchical levels: (1) criteria, (2) attributes, and (3) corresponding questions. The criteria in this framework were usefulness and effectiveness. Usefulness addresses the capability of GD&TIC to improve tolerancing, and effectiveness addresses GD&TIC’s capability to achieve the objective of GD&TIC (i.e., a reduction in tolerance problems caused by the poor communication of tolerance information) while using resources [85]. Two attributes fall under the usefulness criterion, namely practicality [54,86] and applicability [86]. Three attributes fall under the effectiveness criterion, namely acceptability [85,86], efficacy [84,86], and efficiency [84]. The framework consisted of five questions, each question representing an attribute. A verbatim transcription from the recorded focus group was produced. A summary of findings is presented in Section 4.3. All quotations from the focus group are presented in italics and were improved for readability.

Table 4. Framework developed for evaluating usefulness and effectiveness of geometric dimensioning and tolerancing in construction (GD&TIC).

Criteria Attributes Corresponding Questions Does GD&TIC have the potential to be accepted by designers Acceptability and contractors, and to be used in the AEC industry? Effectiveness Is GD&TIC useful in the sense that it will lead to improved Efficacy tolerancing in AEC? Does the time and cost needed to implement GD&TIC outweigh Efficiency the costs saved as a result of eliminated reworks, delays and poor quality? Practicality In terms of clarity and simplicity, is GD&TIC easy to implement? Usefulness Could GD&TIC avoid the tolerance problems identified in Case Practicality A and Case B?

4. Results: Geometric Dimensioning and Tolerancing in Construction (GD&TIC) GD&T is a comprehensive language [87]. GD&TIC is a simplified and refined version of GD&T and is a system prescribed for the communication of tolerance requirements in AEC. The main reason for using the term ‘GD&TIC’ (as opposed to ‘GD&T’) is to emphasise that this system is the refined version of GD&T and was developed specifically for the AEC industry. Four key terms used in GD&TIC are: (1) surface feature, (2) feature of size, (3) datum, and (4) tolerance zone. These are defined as follows. The surface feature and the feature of size are two specific types of features. A geometric tolerance can be applied to a surface feature or a dimensioned feature. The latter type of feature is Buildings 2020, 10, 62 9 of 29 known as a feature of size [88]. The datum is a theoretically exact point, axis, or plane from which the location or geometric characteristics of a feature are established [46]. The tolerance zone is a two or three-dimensional area within which all of the toleranced features are contained [45]. Depending on the type of tolerance applied to a feature, tolerance zones can have different shapes (e.g., circle and cylinder) [46]. Geometric characteristic symbols are the essence of GD&T [17] and, similarly, of GD&TIC. GD&TIC, in this paper, consists of three categories and a set of five symbols. A summary of the fundamentals of GD&TIC is given in Table5. As can be seen in Table5, these symbols fall into three categories: (1) form, (2) orientation, and (3) location. It is worth noting that GD&T has five categories and fourteen symbols [89]. 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Flatness:Perpendicularityamountalong It ofdemonstrates deviation a line. (surface): of the Two3D Tolerance parallel planes, Zone: theForm: shapeFlatness: It establishesof a surface. It demonstrates allowed the amount to have. of Cylindricalmust 3D boundarylie. Tolerance Zone:No limitsFlatness:flatnamount theess Itamo that ofdemonstrates untdeviation a surface of variation of is the whereTwo3D Tolerance theparallel entire planes, Zone: surface the shapeOrientation:deviation of a surface. It of flatness that a surface is 3Dthat ToleranceTwo is directly parallel Zone: planes, Optional whereNo the No Perpendicularityallowedflatnamountallowedess over thatof deviation toaa from surfacehave. (surface): being of is whereTwo theparallelmust entire lie. planes, surface describes the allowed to have. Cylindricalperpendicularentire boundary to surface the mustNo lie. limitsparallel theallowed to amo theunt todatum have. of variation plane. 3D Tolerancemust lie. Zone: relationshipOrientation: between It Perpendicularityflatness that a surface (surface): is wherethatdatum the is entire directly 3Dplane Tolerancesurface Zone:Optional Perpendicularityallowed (surface): over limits a from the being Cylindrical3D Tolerance boundary Zone: featuresdescribes and datums the at limitsPerpendicularityParallelism: theallowed amount toIt limits have.of (surface): variation the perpendicularCylindricalmust lie. to the boundary that is Orientation: It describes Orientation:amount of It variationparallel allowed to the over datum a from plane. Cylindrical3D2Dthat Toleranceor 3D is directlyTolerance boundary Zone: Optional Optional relationshipparticular angles.between limitsamountPerpendicularityallowed the of amoover variationunt a from of (surface): variationallowed being directlydatum perpendicularplane to the datum the relationship between Orientation:describesbeing the It parallel to the datum plane. Zone:Cylindricalperpendicularthat Two is directlyplanes, boundary to the that Optional features and datums at parallelallowedoverParallelism: an to entireover the datumaIt plane, fromlimits beingplane.from the plane Yes features and datums atrelationshipdescribes between the limits the amount of variation areperpendicular2D parallel datumor 3D to Tolerance plane the to datum the particularOrientation:Parallelism: angles. It It limitsbeingamountparallel parallel the ofto amount variationthe to datum the ofreference allowed plane. that2D is or directly 3D Tolerance Optional Zone: Two particular angles. featuresrelationship and datums between at allowedParallelism: over Ita fromlimits being the Zone:datum Twoplane planes, plane that describesvariation the allowed over an an entire entireplane. plane, plane, from perpendicular2D orplanes, 3D Tolerance that to the are parallelYes to the Yes featuresparticular and datumsangles. at amountparallelParallelism: ofto variationthe Itdatum limits allowed plane. the are parallel to the datum relationshipfrom being between parallel being to the parallel reference to the plane. reference Zone:3D2D datumToleranceor Two 3D planes,Tolerance plane Zone:datum that plane featuresparticular and datumsangles. at amountoverParallelism: an of entire variation It plane, limits allowed from the plane Yes plane. areZone:Cylindrical2D parallel or Two 3D toplanes,Tolerance 3Dboundary the Tolerance datum that Zone: Location: It establishesLocation:particular It establishes angles. Tolerancebeingamountover parallel an of entireof variation Position to plane,the reference allowed(TOP): from It Yes Tolerance of Position (TOP): It determines arewhere3D parallel Tolerance theplane central Cylindricalto the Zone: datumaxis of boundary the position of the the position of the beingdetermines parallel plane.the to deviation the reference of a Zone: Two planes, that the deviation of a feature’sover an entire axis fromplane, the from a featureCylindricalwhere ofplane size the boundary must central lie, axis ofYes afeature Yes feature relative to aLocation:feature relative It establishes to a Tolerancefeature’s axis ofplane. Position from the (TOP): Perfect It are3D parallel Tolerance to the Zone: datum Perfectbeing position. parallel to the reference whereconcerningof the size central must the axis lie, of concerning the datum. the positiondatum. of the determinesposition. the deviation of a Cylindrical3D Toleranceplane boundary Zone: Location: It establishes Tolerance ofplane. Position (TOP): It a featuretheoreticallytheoretically of size perfect must perfectlie, location.Yes feature relative to a feature’s axis from the Perfect whereCylindrical the central boundary axis of Location:the position It establishes of the Tolerancedetermines of the Position deviation (TOP): of aIt 3Dconcerning Tolerancelocation. Zone: the datum. position. awhere featureCylindrical the of central size boundary must axis lie, of Yes Location:featuretheLike position relative GD&T,It establishes of theto the a GD&TIC Tolerancefeature’sdetermines system axis of thePosition from usesdeviation the (TOP):a Perfectfeature of aIt control frame theoretically(FCF) to specify perfect information for awhere featureconcerning the of central size mustthe axis lie, of Yes thefeature thegeometric positiondatum. relative controlof theto a of feature’sdeterminesa feature axis position.and the from deviationthereby the Perfect clearlyof a and to visually communicatelocation. how geometric a featuretheoreticallyconcerning of size perfect mustthe lie, Yes The fourth categoryfeatureLikedatum. relativeGD&T, is profile,to the a GD&TICfeature’s which system axisposition. from hasuses the a two Perfectfeature symbols. control frame This (FCF) category to specify information is not presented for in this paper tolerances are applied through drawings [93]. An FCF is a theoretically rectangularconcerninglocation. perfect the box comprised of datum. position. because it can becompartmentsthe indirectly geometricLike GD&T, control where controlledthe GD&TIC of the a geometricfeature systemby and characteristi the usesthereby a form, feature clearlyc symbol, orientation,control and to toleranceframe visually theoretically(FCF) value,communicate andlocation. to specify modifiers locationperfect informationhow , and geometric categories, datum for and, therefore, tolerances are applied through drawings [93]. An FCF is a rectangular box comprised of it is often ignoredthereferences evengeometricLike GD&T, are in controlplaced the the manufacturing GD&TIC[45]of a. featureThe systemFCF and in GD&Tusesthereby a context featureand clearly GD&TIC control and [92 to are ]. framevisually exactly The (FCF) communicate fifthsimilar.location. to specify category Figure informationhow 2 depicts geometric is the thefor runout control that tolerancesFCFthecompartments geometric andLike defines GD&T, are control where appliedeach the GD&TIC symbolof the a through geometricfeature used. system and drawingsThe characteristi usesthereby tolerance a feature[93] clearly modifier.c Asymbol, controln and FCF into toleranceframe FCF isvisually a is rectangular(FCF)out value,communicate of ttheo specify modifiersscope box ofinformationhow comprised this, and geometric research. datum for of is applied to rotatingcompartmentsthetolerancesreferences geometric parts are are control placed where applied [93 [45]of the], a through. whichgeometricfeatureThe FCF and drawings in arecharacteristi GD&Tthereby scares [93]and clearlyc. GD&TIC symbol, A inn and FCF the to toleranceare visually is AECexactly a rectangular value,communicate similar. industry. modifiers Figure box how comprised ,2 Even anddepicts geometric datum whenthe of buildings have FCF and defines each symbol used. The tolerance modifier in FCF is out of the scope of this research. rotating parts (e.g.,referencestolerancescompartments a revolving are are placed where applied [45] the restaurant), through. geometricThe FCF drawings in characteristi GD&T the [93]and tolerancingc. GD&TIC symbol, An FCF are tolerance is exactly a rectangular of value, similar. those modifiers Figure box parts comprised 2, anddepicts is datum expected the of to be handled FCFcompartmentsreferences and defines are placed where each symbol[45] the . geometricThe used. FCF Thein characteristi GD&T tolerance and modifierc GD&TIC symbol, in are toleranceFCF exactly is out value, similar.of the modifiersscope Figure of this,2 anddepicts research. datum the by mechanical engineersreferencesFCF and defines are placed and each notsymbol[45]. The the used. FCF AEC Thein GD&T tolerance people and modifier GD&TIC [20]. in are Hence,FCF exactly is out similar.of this the scope categoryFigure of this2 depicts research. and the its two symbols do not seem to haveFCF relevant and defines each application symbol used. The to t theolerance AEC modifier industry. in FCF is out The of the other scope of symbols,this research. namely circularity 1. Leader arrow: The arrow points to the feature to which the geometric control is applied.

(roundness) and cylindricity2. Geometric symbol: under This the indicates form the category;type of specified concentricity geometric control. and symmetry under the location 3.1. DiameterLeader arrow: symbol The (if arrow required): points This to the indicates feature a to cylindrica which thel tolerance geometric zone. control is applied. category; and angularity under the orientation category, were excluded from the preliminary version 1.4.2. LeaderToleranceGeometric arrow: value: symbol: The This arrow This indicates indicates points the to the thetotal type feature tolerance of specified to which of the geometric thegeometric geometric control. control. control is applied. of GD&TIC presented2.5.1.3. GeometricToleranceLeaderDiameter in arrow: this s msymbolymbol:odifier The research (if arrowThis(if required): required) indicates pointspaper. This to the the indicates type feature Thisof specifieda to cylindrica which isbecause geometric thel tolerance geometric control. they zone. control can is applied. be indirectly controlled by other GD&T symbols.3.1.6.2.4. DiameterLeaderPrimaryGeometricTolerance More a rrow:d s atum value:ymbolsymbol: specifically, The (if This (if arrowrequired):This required): indicates indicates points This Thiscircularitythe to the indicatesthetotal indicates type feature tolerance of the specifieda to cylindrica andmain which of the datum. cylindricitygeometric the geometricl tolerance geometric The control. datumcontrol. zone. control can letter is becorrespondsapplied. controlled by straightness, 4.2.3.5. ToleranceGeometrictoDiameter a feature svalue: mymbols onymbol:odifier the This (if part This(if required): indicates required) which indicates i sThisthe ma the total rkedindicates type tolerancewith of specified athe cylindrica sameof the geometric letter. geometricl tolerance control. control. zone. concentricity can5.3.4.6. be ToleranceDiameterPrimary controlled d smvalue:atumymbolodifier (if byThis (if required):(if required): position, indicatesrequired) This Thisthe indicatestotal symmetryindicates tolerance the a cylindrica main of the can datum. geometricl tolerance be The controlled datumcontrol. zone. letter corresponds by a combination of position 6.4.5. PrimaryToleranceto a feature d atumvalue:m onodifier the (if This partrequired): (if indicatesrequired) which This i sthe ma indicatestotalrked tolerancewith the the main sameof the datum. letter. geometric The datumcontrol. letter corresponds and parallelism, and angularityFigure 2. Illustration can be of a controlledfeature control frame by and parallelism definition of its symbols and/ [10]or. perpendicularity. Moreover, 5.6. toTolerancePrimary a feature d atumm onodifier the (if part required):(if required) which Thisis ma indicatesrked with the the main same datum. letter. The datum letter corresponds no application could4.16.. TypesPrimaryto be a featureof found TFigu olerancesdatum reon 2. thefor Illustration(if partandrequired): those Gwhicheometric of a symbols This ifeatures ma Cindicatesrkedharacteristics control with given framethe the main sameand in the GD&TIC definitiondatum. letter. nature The of its datum symbols of assemblies letter [10] .corresponds in construction and the

to a featureFigu reon 2. the Illustration part which of a featureis marked control with frame the sameand definition letter. of its symbols [10]. purpose of the symbols4.1.1.4.1. Types Form of based Tolerances on and the Geometric findings Characteristics during in the GD&TIC literature review and empirical studies. Figure 2. Illustration of a feature control frame and definition of its symbols [10]. Like GD&T,4.1 the. Types GD&TIC of TFiguolerancesre 2. Illustration system and Geometric of a uses feature Characteristics acontrol feature frame and in control GD&TIC definition of frame its symbols (FCF) [10]. to specify information for 4.1.1. Form the geometric control4.1. Types of of T aolerances feature and and Geometric thereby Characteristics clearly in GD&TIC and to visually communicate how geometric 4.1.1.4 .1. Types Form of Tolerances and Geometric Characteristics in GD&TIC tolerances are applied 4.1.1. Form through drawings [93]. An FCF is a rectangular box comprised of compartments 4.1.1. Form where the geometric characteristic symbol, tolerance value, modifiers, and datum references are placed [45]. The FCF in GD&T and GD&TIC are exactly similar. Figure2 depicts the FCF and defines each symbol used. The tolerance modifier in FCF is out of the scope of this research. Buildings 2020, 10, x FOR PEER REVIEW 10 of 33

Table 5. A summary of the rules and terms of GD&TIC.

Datum Type of Tolerance Geometric Characteristics Symbols Tolerance Zone Required Straightness: It represents 2D Tolerance Zone: how straight a surface is on No Two parallel lines along a line. Form: It establishes Flatness: It demonstrates the 3D Tolerance Zone: the shape of a surface. amount of deviation of Two parallel planes, No flatness that a surface is where the entire surface allowed to have. must lie. 3D Tolerance Zone: Perpendicularity (surface): Cylindrical boundary limits the amount of variation Orientation: It that is directly Optional allowed over a from being describes the perpendicular to the parallel to the datum plane. relationship between datum plane features and datums at Parallelism: It limits the 2D or 3D Tolerance particular angles. amount of variation allowed Zone: Two planes, that over an entire plane, from Yes are parallel to the datum being parallel to the reference plane plane. 3D Tolerance Zone: Cylindrical boundary Location: It establishes Tolerance of Position (TOP): It where the central axis of the position of the determines the deviation of a a feature of size must lie, Yes feature relative to a feature’s axis from the Perfect concerning the datum. position. theoretically perfect location. Like GD&T, the GD&TIC system uses a feature control frame (FCF) to specify information for the geometric control of a feature and thereby clearly and to visually communicate how geometric tolerances are applied through drawings [93]. An FCF is a rectangular box comprised of Buildings 2020compartments, 10, 62 where the geometric characteristic symbol, tolerance value, modifiers, and datum 10 of 29 references are placed [45]. The FCF in GD&T and GD&TIC are exactly similar. Figure 2 depicts the FCF and defines each symbol used. The tolerance modifier in FCF is out of the scope of this research.

1. Leader arrow: The arrow points to the feature to which the geometric control is applied. 2. Geometric symbol: This indicates the type of specified geometric control. 3. Diameter symbol (if required): This indicates a cylindrical tolerance zone. 4. Tolerance value: This indicates the total tolerance of the geometric control. 5. Tolerance modifier (if required) 6. Primary datum (if required): This indicates the main datum. The datum letter corresponds to a feature on the part which is marked with the same letter.

FigureFigure 2. Illustration 2. Illustration of aof feature a feature control control frame and and definition definition of its of symbols its symbols [10]. [10].

4.1. Types4.1. of Types Tolerances of Tolerances and Geometric and Geometric Characteristics Characteristics in GD&TIC in GD&TIC

Buildings4.1.1. Form 20204.1.1., 10Form, x FOR PEER REVIEW 11 of 33 The form establishes the shape of a surface [88] [88] and is described described here by means of two two geometric geometric characteristics: (1) (1) straightness straightness and and (2) (2) flatness flatness [89]. [89]. These These characteristics characteristics never never use use a a datum datum [89]. [ 89].

Straightness The straightness controlcontrol can can be be applied applied to to a surfacea surface [93 [93].]. Straightness Straightness is ais condition a condition where where the linethe lineelements elements of a surfaceof a surface follow follow a straight a straight line and line satisfy and satisfy the specified the specified tolerances tole [46rances]. In simple[46]. In terms, simple a terms,straightness a straightness control represents control repr howesents straight how astraight surface a is surface along a is line. along When a line. a straightness When a straightness control is controlapplied is to applied a surface, to ita demonstratessurface, it demonstrates the permitted the deviationpermitted of deviation the straightness of the straightness in each surface in each line surfaceelement line [17]. element The tolerance [17]. The zone tolerance for a straightness zone for a control straightness applied control to a surface applied is two-dimensional to a surface is two- and dimensionalincludes two and parallel includes lines two for theparallel line elementlines for ofthe the line surface element [93 ].of The the twosurface highest [93]. pointsThe two of thehighest line pointselement of ofthe the line surface element create of the the surface first line create element the first of the line tolerance element zone. of the The tolerance distance zone. between The distance the two betweenparallel lines the two of the parallel tolerance lines zone of the is equal tolerance to the zone straightness is equal toleranceto the straightness value. The tolerance second line value. element The secondof the tolerance line element zone of is the at thetolerance bottom zone of the is at line the element bottom of of the the surface, line element parallel of the to the surface, first line, parallel and tooff theset byfirst the line, straightness and offset toleranceby the straightness value. The tole tolerancerance value. zone The for thetolerance straightness zone for controls the straightness delimits a controlsrange of delimits variation a up range and downof variation in a Y-axis up and over down the line in elementa Y-axis ofover the the surface line [element17]. If the of linethe elementsurface [17].of the If surfacethe line is element within theof the two surface parallel is line within elements the two of theparallel tolerance line elements zone, then of the the feature tolerance is within zone, thentolerance the feature [19]. Figure is within3 shows tolerance the tolerance [19]. Figure zone 3 for shows a steel the beam tolerance to which zone the for straightness a steel beam control to which has thebeen straightness applied (related control to Tolerancehas been Problemapplied (related 3). The distance to Tolerance of 15 mmProblem between 3). The the twodistance parallel of 15 lines mm of betweenthe tolerance the two zone parallel represents lines the of the straightness tolerance tolerancezone represents value. the straightness tolerance value.

FigureFigure 3. 3. ToleranceTolerance zone for the straightness control applied to a steel beam.

It is is proposed proposed that th thee straightness co controlntrol in GD&TIC is used to control the beams and columns that are prone to deformation as a result of the dead and imposed loads. These deformations include beam deflection deflection and column buckling, which can potentially result in the components being out of tolerance. Figure Figure 44aa showsshows aa steelsteel frameframe structurestructure withwith thethe straightnessstraightness controlcontrol appliedapplied toto itsits beambeam inin the envelope, and Figure 4 4bb showsshows thethe associatedassociated tolerancetolerancezone zone(related (related to to Tolerance Tolerance Problem Problem 3). 3).

(a) (b)

Figure 4. (a) Straightness control applied to a beam in a steel frame structure; (b) straightness control and its associate tolerance zone.

Flatness Flatness is a condition where a surface has all its elements in one plane [94], which indicates a condition of being completely a planar surface. When a flatness control is applied to a surface, it demonstrates the amount of deviation in flatness that a surface is allowed to have [94]. When the

Buildings 2020, 10, x FOR PEER REVIEW 11 of 33

The form establishes the shape of a surface [88] and is described here by means of two geometric characteristics: (1) straightness and (2) flatness [89]. These characteristics never use a datum [89].

Straightness The straightness control can be applied to a surface [93]. Straightness is a condition where the line elements of a surface follow a straight line and satisfy the specified tolerances [46]. In simple terms, a straightness control represents how straight a surface is along a line. When a straightness control is applied to a surface, it demonstrates the permitted deviation of the straightness in each surface line element [17]. The tolerance zone for a straightness control applied to a surface is two- dimensional and includes two parallel lines for the line element of the surface [93]. The two highest points of the line element of the surface create the first line element of the tolerance zone. The distance between the two parallel lines of the tolerance zone is equal to the straightness tolerance value. The second line element of the tolerance zone is at the bottom of the line element of the surface, parallel to the first line, and offset by the straightness tolerance value. The tolerance zone for the straightness controls delimits a range of variation up and down in a Y-axis over the line element of the surface [17]. If the line element of the surface is within the two parallel line elements of the tolerance zone, then the feature is within tolerance [19]. Figure 3 shows the tolerance zone for a steel beam to which the straightness control has been applied (related to Tolerance Problem 3). The distance of 15 mm between the two parallel lines of the tolerance zone represents the straightness tolerance value.

Figure 3. Tolerance zone for the straightness control applied to a steel beam.

It is proposed that the straightness control in GD&TIC is used to control the beams and columns that are prone to deformation as a result of the dead and imposed loads. These deformations include beam deflection and column buckling, which can potentially result in the components being out of Buildingstolerance.2020, 10, 62 Figure 4a shows a steel frame structure with the straightness control applied to its beam in 11 of 29 the envelope, and Figure 4b shows the associated tolerance zone (related to Tolerance Problem 3).

(a) (b)

FigureFigure 4. (a) Straightness4. (a) Straightness control control applied applied to to aa beam in in a asteel steel frame frame structure; structure; (b) straightness (b) straightness control control and itsand associate its associate tolerance tolerance zone. zone.

FlatnessFlatness Flatness is a condition where a surface has all its elements in one plane [94], which indicates a Flatness is a condition where a surface has all its elements in one plane [94], which indicates a condition of being completely a planar surface. When a flatness control is applied to a surface, it conditiondemonstrates of being the completely amount of adeviation planar surface.in flatness Whenthat a surface a flatness is allowed control to ishave applied [94]. When to a the surface, it demonstrates the amount of deviation in flatness that a surface is allowed to have [94]. When the flatness Buildings of a component 2020, 10, x FOR PEER is critical, REVIEW such as the whole or part of a floor surface, the flatness12 of 33 control is applied flatness [92], of regardless a component of is thecritical, thickness, such as the the whole size or dimension, part of a floor or surface, other featuresthe flatness that control may is also be Buildings 2020, 10, x FOR PEER REVIEW 12 of 33 specifiedapplied [17]. [92], When regardless the flatness of the controlthickness, is the applied, size dimension, the tolerance or other value features for flatnessthat may isalso specified be to specified [17]. When the flatness control is applied, the tolerance value for flatness is specified to ensure thatflatness the of surface a component does notis critical, undulate such as beyond the whole the or specified part of a floor limit surface, [95]. Figure the flatness5 shows control a concrete is ensure that the surface does not undulate beyond the specified limit [95]. Figure 5 shows a concrete slab containingapplied [92], a flatness regardless callout of the of 5th mmickness, (related the size to dimension, Tolerance Problemor other features 1). that may also be slab containing a flatness callout of 5 mm (related to Tolerance Problem 1). specified [17]. When the flatness control is applied, the tolerance value for flatness is specified to ensure that the surface does not undulate beyond the specified limit [95]. Figure 5 shows a concrete slab containing a flatness callout of 5 mm (related to Tolerance Problem 1).

FigureFigure 5. Flatness 5. Flatness control control applied applied to either either view view of ofa concrete a concrete slab. slab.

The toleranceThe tolerance zone zone for thefor the flatness flatness control control isis three-dimensional and and comprises comprises two parallel two parallel Figure 5. Flatness control applied to either view of a concrete slab. planes [planes19]. The [19]. elements The elements of the of the surface surface being being controlledcontrolled must must lie lie within within the two the parallel two parallel planes planes[93]. [93]. The first theoretical plane of the tolerance zone is created by considering the three highest points of The first theoreticalThe tolerance plane zone of the for tolerance the flatness zone control is created is three-dimensional by considering and the comprises three highest two parallel points of the the controlled surface. The second theoretical plane of the tolerance zone is parallel to the first plane controlledplanes surface. [19]. The The elements second of theoretical the surface being plane contro of thelled tolerance must lie within zone isthe parallel two parallel to the planes first [93]. plane [17], [17], and the distance between the parallel planes is equal to the flatness tolerance value [93]. If the and theThe distance first theoretical between plane the parallel of the tolerance planes zone is equal is created to the by flatness considering tolerance the three value highest [93 points]. If the of points points of the controlled surface lie within the tolerance zone, then the surface being controlled is the controlled surface. The second theoretical plane of the tolerance zone is parallel to the first plane of the controlledwithin the surfaceflatness tolerance lie within [94]. the The tolerance flatness cont zone,rol, thenlike other the form surface tolerances, being controlledcreates a tolerance is within the [17], and the distance between the parallel planes is equal to the flatness tolerance value [93]. If the flatnesszone tolerance that is [never94]. Therelative flatness to a datum control, [48]. like other form tolerances, creates a tolerance zone that is points of the controlled surface lie within the tolerance zone, then the surface being controlled is Figure 6 shows a concrete slab with a flatness callout of 5 mm. The feature in this concrete slab never relativewithin the to aflatness datum tolerance [48]. [94]. The flatness control, like other form tolerances, creates a tolerance relates to the top surface. The surface must stay entirely within the tolerance zone of 5 mm to be Figurezone6 thatshows is never a concrete relative to slab a datum with [48]. a flatness callout of 5 mm. The feature in this concrete slab within tolerance. Figure 6 shows a two-dimensional cross section whose surface can vary by up to 5 relates to theFigure top surface. 6 shows Thea concrete surface slab must with stay a flatness entirely callout within of 5 mm. the toleranceThe feature zone in this of concrete 5 mm to slab be within mm within the tolerance zone (related to Tolerance Problem 1). tolerance.relates Figure to the6 showstop surface. a two-dimensional The surface must crossstay en sectiontirely within whose the surfacetolerance can zone vary of 5 bymm up to tobe 5 mm within thewithin tolerance tolerance. zone Figure (related 6 shows to a Tolerance two-dimensional Problem cross 1). section whose surface can vary by up to 5 mm within the tolerance zone (related to Tolerance Problem 1).

Figure 6. Two-dimensional cross section showing the tolerance zone for the flatness control applied to a concrete slab.

Figure 6.FigureTwo-dimensional 6. Two-dimensional cross cross section section showing showing the the tolerance tolerance zone for for the the flatness flatness control control applied applied to 4.1.2. Orientation Tolerances a concreteto a slab. concrete slab. Parallelism and perpendicularity are the orientation symbols used in GD&TIC. These symbols describe4.1.2. Orientation the relationship Tolerances between features and datums at particular angles [96]. Parallelism and perpendicularity are the orientation symbols used in GD&TIC. These symbols Parallelism (Surface) describe the relationship between features and datums at particular angles [96]. Parallelism is a condition of a surface, centre plane, or an axis that is equidistant at all points fromParallelism a datum (Surface) plane [19]. A parallelism (surface) control limits the amount of variation allowed over an entire plane, from a state of being parallel to the datum plane [87]. In conventional drawings, the Parallelism is a condition of a surface, centre plane, or an axis that is equidistant at all points size dimension between two surfaces controls the parallelism if those two surfaces are shown to be from a datum plane [19]. A parallelism (surface) control limits the amount of variation allowed over parallel on a drawing. However, this method has two shortcomings. The first shortcoming relates to an entire plane, from a state of being parallel to the datum plane [87]. In conventional drawings, the the size requirement and the parallelism requirement as they are assumed to be similar, while in size dimension between two surfaces controls the parallelism if those two surfaces are shown to be reality they may have different values in order to ensure the functionality [97]. Figure 7a shows a parallel on a drawing. However, this method has two shortcomings. The first shortcoming relates to drawing of a doorway in an industrial building (related to Tolerance Problem 4). The posts at the two the size requirement and the parallelism requirement as they are assumed to be similar, while in sides of the doorway may be within size tolerance, but the parallelism tolerance may need to be reality they may have different values in order to ensure the functionality [97]. Figure 7a shows a drawing of a doorway in an industrial building (related to Tolerance Problem 4). The posts at the two

sides of the doorway may be within size tolerance, but the parallelism tolerance may need to be

Buildings 2020, 10, x FOR PEER REVIEW 13 of 33

tighter to ensure that there is an adequate distance between the posts to accommodate the door whilst also ensuring that there are no gaps around the door (Figure 7b). Further to this, when the size tolerance is satisfied, it does not necessarily ensure that the two sides of the doorway are in a plane Buildings 2020, 10, 62 12 of 29 (Figure 8). The second of these shortcomings relates to when parallelism is implied by using a size 4.1.2.dimension, Orientation as the datum Tolerances is not specified [96]. This can result in confusion, as the modification process is highly dependent on the measurement results and a lack of datum can cause different Parallelism and perpendicularity are the orientation symbols used in GD&TIC. These symbols measurement results [89]. In Figure 8, the datum can be positioned to either side of the doorway and describe the relationship between features and datums at particular angles [96]. determines whether the right side or the left side of the doorway is out of alignment. Parallelism (Surface) Parallelism is a condition of a surface, centre plane, or an axis that is equidistant at all points from a datum plane [19]. A parallelism (surface) control limits the amount of variation allowed over an Buildingsentire 2020 plane,, 10, xfrom FOR PEER a state REVIEW of being parallel to the datum plane [87]. In conventional drawings,13 of 33 the size dimension between two surfaces controls the parallelism if those two surfaces are shown to be parallel tighter to ensure that there is an adequate distance between the posts to accommodate the door whilst on a drawing. However, this method has two shortcomings. The first shortcoming relates to the size also ensuring that there are no gaps around the door (Figure 7b). Further to this, when the size tolerancerequirement is satisfied, and the it does parallelism not necessarily requirement ensure as that they the are two assumed sides of to the be doorway similar, whileare in a in plane reality they (Figuremay have8). different values in order to ensure the functionality [97]. Figure7a shows a drawing of a doorwayThe second in an of industrial these shortcomings building (related relates to to Tolerance when parallelism Problem 4). is Theimplied posts by at theusing two a sidessize of the dimension,doorway as may the bedatum within is not size specified tolerance, [96]. but This the can parallelism result in confusion, tolerance as may the needmodification to be tighter process to ensure is thathighly there dependent is an adequate on the distance measurement between resu thelts posts and to a accommodate lack of datum the can door cause whilst different also ensuring measurementthat there are results no gaps [89]. around In Figure the 8, door the datum (Figure can7b). be Further position toed this, to either when side the of size the tolerance doorway isand satisfied, determinesit does not whether necessarily the right ensure side that or the the left two side sides of the of thedoorway doorway is out are of in alignment. a plane (Figure 8).

(a) (b)

Figure 7. (a) A doorway in an industrial building; (b) the doorway when its posts are at the extreme Figure 7. (a) A doorway in an industrial building; (b) the doorway when its posts are at the extreme allowed distance. allowed distance.

Figure 8. The lack of alignment between the two sides of the doorway while the specified size tolerance Figure 8. The lack of alignment between the two sides of the doorway while the specified size is satisfied. tolerance is satisfied. (a) (b) The second of these shortcomings relates to when parallelism is implied by using a size dimension, In terms of the application of parallelism (surface), when two surfaces should maintain a asFigure the datum 7. (a) A is doorway not specified in an industrial [96]. This building; can result (b) the in doorway confusion, when as its the posts modification are at the extreme process is highly constantallowed distance, distance. the parallelism control is used. For instance, when it is a functional requirement dependent on the measurement results and a lack of datum can cause different measurement results [89]. In Figure8, the datum can be positioned to either side of the doorway and determines whether the right side or the left side of the doorway is out of alignment. In terms of the application of parallelism (surface), when two surfaces should maintain a constant distance, the parallelism control is used. For instance, when it is a functional requirement that

Figure 8. The lack of alignment between the two sides of the doorway while the specified size tolerance is satisfied.

In terms of the application of parallelism (surface), when two surfaces should maintain a constant distance, the parallelism control is used. For instance, when it is a functional requirement

Buildings 2020, 10, x FOR PEER REVIEW 14 of 33

that doorframes stay equidistant, the parallelism control is then required. This control specifies that (1) the surfaces of those components must be parallel with each other and (2) by how much the components can be offset relative to each other whilst still functioning properly (related to Tolerance Problem 4). The FCF of the parallelism control contains a parallelism symbol, a tolerance value, and a datum feature [93]. Figure 9a shows two walls separated by a door. The drawing callout for a parallelism of 5 mm is applied to Wall 2 (similar to Tolerance Problem 4). In Figure 9b, Wall 1 is set as the datum, and, therefore, the front surface of Wall 2 is referenced parallel in relation to Wall 1. Buildings 2020The, 10 ,tolerance 62 zone for parallelism is two-or three-dimensional, and it comprises two13 ofparallel 29 planes that are parallel to the datum plane [91]. The tolerance zone for the walls illustrated in Figure 9a is shown in Figure 9b (similar to Tolerance Problem 4). The two parallel and dotted lines doorframes stay equidistant, the parallelism control is then required. This control specifies that (1) the demonstrate the tolerance zone for Wall 2. The tolerance zone planes are offset by the tolerance value surfaces of those components must be parallel with each other and (2) by how much the components [98], which, in this example, is 5 mm. The datum is the plane on the front surface of Wall 1. The can be offset relative to each other whilst still functioning properly (related to Tolerance Problem 4). tolerance zone is parallel to the surface of datum A according to the definition of the tolerance zone The FCF of the parallelism control contains a parallelism symbol, a tolerance value, and a datum for parallelism. The feature, which is the front surface of Wall 2, is within tolerance, providing that feature [93]. Figure9a shows two walls separated by a door. The drawing callout for a parallelism of 5 all its elements fit between the tolerance zone of 5 mm. Both walls fall within the tolerance zone, and, mm is applied to Wall 2 (similar to Tolerance Problem 4). In Figure9b, Wall 1 is set as the datum, and, therefore, the front surface of Wall 2 is in tolerance and parallel with Wall 1. therefore, the front surface of Wall 2 is referenced parallel in relation to Wall 1.

(a) (b)

FigureFigure 9. (a) 9. Parallelism (a) Parallelism (surface) (surface) control control applied applied to two to separatetwo separate walls; walls; (b) cross (b) cross section section of the of walls the walls depicteddepicted in Figure in Figure9a and 9a the and associated the associated parallelism parallelism tolerance tolerance zone. zone.

PerpendicularityThe tolerance zone for parallelism is two-or three-dimensional, and it comprises two parallel planes that are parallel to the datum plane [91]. The tolerance zone for the walls illustrated in Figure9a is shown inPerpendicularity Figure9b (similar is toa condition Tolerance used Problem to ensure 4). The th twoat a parallel surface and or axis dotted is exactly lines demonstrate at a right angle the tolerancerelative zoneto a fordatum Wall 2.plane The tolerance[19]. It zoneis herein planes areindicated offset by as the perpendicularity tolerance value [98(surface)], which, and in thisperpendicularity example, is 5 mm. (axis). The The datum perpendicularity is the plane oncontrol the front limits surface the amount of Wall of 1. variation The tolerance allowed zone over a is parallelsurface to or the axis surface from of the datum situation A according of being to parallel the definition to the datum of the toleranceplane [99]. zone This for condition parallelism. is used The feature,when a which feature is theneeds front to surface be perpendicular of Wall 2, is within to another tolerance, feature providing [99]. thatIt is all suggested its elements that fit the betweenperpendicularity the tolerance zone(axis) of control 5 mm. is Both mainly walls used fall for within columns the tolerance located zone,in the and, building therefore, envelope the front or other surfacecolumns of Wall for 2 iswhich in tolerance plumbness and parallel tolerances with are Wall a 1.major concern. This control specifies (1) that the plumbness of those columns is of prime importance for the proper functioning of a mating Perpendicularitycomponent (e.g., cladding) and (2) how much variation of the columns can take place whilst ensuring that the sub-assembly (e.g., the sub-assembly comprised of the cladding installations and columns) Perpendicularity is a condition used to ensure that a surface or axis is exactly at a right angle functions properly. relative to a datum plane [19]. It is herein indicated as perpendicularity (surface) and perpendicularity The perpendicularity (surface) control can predominantly be applied interior partition walls and (axis). The perpendicularity control limits the amount of variation allowed over a surface or axis from cladding panels. This control specifies how much variation can be applied to those components and the situation of being parallel to the datum plane [99]. This condition is used when a feature needs how much they can be out of the plumb relative to the floor surface, which acts as the datum. to be perpendicular to another feature [99]. It is suggested that the perpendicularity (axis) control is However, the application of the perpendicularity control is not limited to these two cases and should mainly used for columns located in the building envelope or other columns for which plumbness be used whenever appropriate. A perpendicularity (surface) control is a three-dimensional tolerance tolerances are a major concern. This control specifies (1) that the plumbness of those columns is of zone. It comprises two parallel planes oriented at 90˚ relative to a datum plane [19]. The distance prime importance for the proper functioning of a mating component (e.g., cladding) and (2) how much variation of the columns can take place whilst ensuring that the sub-assembly (e.g., the sub-assembly comprised of the cladding installations and columns) functions properly. The perpendicularity (surface) control can predominantly be applied interior partition walls and cladding panels. This control specifies how much variation can be applied to those components and how much they can be out of the plumb relative to the floor surface, which acts as the datum. However, the application of the perpendicularity control is not limited to these two cases and should be used whenever appropriate. A perpendicularity (surface) control is a three-dimensional tolerance zone. It comprises two parallel planes oriented at 90◦ relative to a datum plane [19]. The distance between the parallel planes equates to the perpendicularity (surface) tolerance value [93]. Figure 10a shows the tolerance zone for a stone panel used in a cladding system to which the perpendicularity (surface) of Buildings 2020, 10, x FOR PEER REVIEW 15 of 33

between the parallel planes equates to the perpendicularity (surface) tolerance value [93]. Figure 10a Buildings 2020, 10, 62 14 of 29 shows the tolerance zone for a stone panel used in a cladding system to which the perpendicularity (surface) of 10 mm has been applied (related to Tolerance Problem 2). The tolerance zone is 10 mmperpendicular has been applied to the floor (related surface, to Tolerance and the tolerance Problem 2).zone The planes tolerance are 10 zone mm is apart. perpendicular The feature, to thewhich flooris surface,the side and surface the tolerance of the stone zone cladding, planes are is 10 within mm apart. tolerance, The feature, providing which that is theit fits side entirely surface in of the thetolerance stone cladding, zone of is 10 within mm. tolerance, providing that it fits entirely in the tolerance zone of 10 mm.

(a) (b)

FigureFigure 10. (10.a) Perpendicularity(a) Perpendicularity (surface) (surface) tolerance tolerance zone zone applied applied to ato stone a stone panel panel used used in a in cladding a cladding system;system; (b) perpendicularity(b) perpendicularity tolerance tolerance zone zone applied applied to a to column. a column.

PerpendicularityPerpendicularity (feature (feature of size)of size) is ais three-dimensionala three-dimensional tolerance tolerance zone zone in in which which the the amount amount of of variationvariation ofof aa feature’s feature’s central central axis, axis, oriented oriented at at 90 90◦ to˚ to a datum,a datum, is controlled.is controlled. In In Figure Figure 10 b,10b, the the perpendicularityperpendicularity callout callout has has been been applied applied to ato column a column (related (related to Toleranceto Tolerance Problem Problem 2). 2). When When a a perpendicularityperpendicularity control control is applied is applied to a to column, a column, it controls it controls the the axis axis of that of that column column (feature) (feature) [100 [100].]. The The tolerancetolerance zone zone for for an axialan axial control control is a is cylinder a cylinder with wi theth the diameter diameter equal equal to the to the tolerance tolerance [45]. [45]. The The tolerancetolerance zone zone is perpendicular is perpendicular to the to the datum datum plane plane and an thed the feature feature axis axis should should lie withinlie within the the tolerance tolerance zonezone of 5 of mm. 5 mm. To distinguishTo distinguish between between perpendicularity perpendicularity (axis) (axis) and and perpendicularity perpendicularity (surface), (surface), a correct a correct FCF FCF shouldshould be applied. be applied. The The FCF FCF for perpendicularity for perpendicularity (surface) (surface) control control must pointmust directlypoint directly to the surface to the [surface45]. The[45]. leader The arrow leader can arrow reference can anyreference view onany the view drawing on the because drawing the entirebecause side the surface entire is side referenced surface is perpendicular.referenced perpendicular. The FCF of the The perpendicularity FCF of the (surface)perpendicularity control contains(surface) the control perpendicularity contains the symbol,perpendicularity a tolerance value,symbol, and a atolerance datum feature value, [and93]. a Figure datum 11 afeature shows [93]. a stone Figure cladding 11a shows where a the stone perpendicularityBuildingscladding 2020, 10where, x FOR (surface) the PEER perpendicularity REVIEW control has been (surface) applied control (related has to been Tolerance applied Problem (related 2). to Tolerance16 Problem of 33 2). The FCF of the perpendicularity (axis) control contains the perpendicularity symbol, a diameter sign, a tolerance value, and a datum feature [93], if necessary. The reason for the presence of the diameter sign in the FCF is that whenever a feature is axial and the tolerance zone is cylindrical, it requires the use of the diameter symbol (Ø) [100]. Apparently, the diameter symbol in the FCF of the perpendicularity (surface), for which the tolerance zone comprises two parallel planes, is not needed. Figure 11b shows that the perpendicularities (axis) controls of 15 and 20 mm have been applied to the columns in the envelope of a building (related to Tolerance Problem 2).

(a) (b)

Figure 11.11. ((aa)) PerpendicularityPerpendicularity (surface) (surface) control control applied applied to ato stone a stone cladding; cladding; (b) perpendicularity (b) perpendicularity (axis) control(axis) control applied applied to the to columns the columns in the envelopein the envelope of a building. of a building.

4.1.3.The Location FCF of Tolerances the perpendicularity (axis) control contains the perpendicularity symbol, a diameter sign, a tolerance value, and a datum feature [93], if necessary. The reason for the presence of the diameter Tolerance sign inof theposition FCF is (TOP) that whenevercontrol is among a feature the is location axial and tolerances. the tolerance It establishes zone is cylindrical, the position it of the feature relative to a datum [92].

Tolerance of Position (TOP) Prior to defining the tolerance of position (TOP) control, the definition for the perfect position should be established. The perfect position specifies the exact location of a feature of size in space. The perfect position of each feature is given on drawings by basic dimensions, and it is the exact location of the feature. The TOP control is the location tolerance of a feature of size relative to its perfect position [17,46]. In other words, it determines how far away a feature’s axis can deviate from the perfect position, which is a theoretically perfect location. When the TOP control is applied to a feature of size, the basic dimension must specify the perfect position of the axis or centreplane of the feature of size [101]. This control indicates the tolerance zone surrounding the perfect position and it is centred on this zone. Hence, the perfect position refers to the exact point that it is targeted, while the TOP control refers to the area surrounding the point [89]. The tolerance zone of the TOP control is cylindrical [102]. Figure 12a shows a three-dimensional column where the TOP control has been applied (related to Tolerance Problem 6). The perfect position, which is the central axis of the column, can be seen going through the column. The cylindrical tolerance zone of the TOP control is centred on the perfect position of the controlled feature [101]; in other words, half of the width of the tolerance zone is on either side of the datum feature centre line. The feature is allowed to vary within the width zone from side-to-side. Hence, the tolerance zone exists around the central axis. The diameter of the cylindrical tolerance zone equates to the tolerance value assigned for the TOP control [103].

Buildings 2020, 10, 62 15 of 29

requires the use of the diameter symbol (Ø) [100]. Apparently, the diameter symbol in the FCF of the perpendicularity (surface), for which the tolerance zone comprises two parallel planes, is not needed. Figure 11b shows that the perpendicularities (axis) controls of 15 and 20 mm have been applied to the columns in the envelope of a building (related to Tolerance Problem 2).

4.1.3. Location Tolerances Tolerance of position (TOP) control is among the location tolerances. It establishes the position of the feature relative to a datum [92].

Tolerance of Position (TOP) Prior to defining the tolerance of position (TOP) control, the definition for the perfect position should be established. The perfect position specifies the exact location of a feature of size in space. The perfect position of each feature is given on drawings by basic dimensions, and it is the exact location of the feature. The TOP control is the location tolerance of a feature of size relative to its perfect position [17,46]. In other words, it determines how far away a feature’s axis can deviate from the perfect position, which is a theoretically perfect location. When the TOP control is applied to a feature of size, the basic dimension must specify the perfect position of the axis or centreplane of the feature of size [101]. This control indicates the tolerance zone surrounding the perfect position and it is centred on this zone. Hence, the perfect position refers to the exact point that it is targeted, while the TOP control refers to the area surrounding the point [89]. The tolerance zone of the TOP control is cylindrical [102]. Figure 12a shows a three-dimensional column where the TOP control has been applied (related to Tolerance Problem 6). The perfect position, which is the central axis of the column, can be seen going through the column. The cylindrical tolerance zone of the TOP control is centred on the perfect position of the controlled feature [101]; in other words, half of the width of the tolerance zone is on either side of the datum feature centre line. The feature is allowed to vary within the width zone from side-to-side. Hence, the tolerance zone exists around the central axis. The diameter of the cylindrical tolerance zone equates to the tolerance value assigned for Buildingsthe 2020 TOP, 10, controlx FOR PEER [103 REVIEW]. 17 of 33

(a) (b)

FigureFigure 12. (a) 12. Tolerance(a) Tolerance zone zone of the of thetolerance tolerance of ofposition position (TOP) (TOP) control control applied applied toto aa column; column; (b ()b position) positionof of the the referenced referenced column column relative relative to to datums. datums.

UnlikeUnlike orientation orientation symbols, symbols, the location the location of the oftolerance the tolerance zone of zone the ofTOP the control TOP control is established is established relativerelative to a datum. to a datum. Figure Figure 12b shows 12b shows the same the samecolumn column in a two-dimensional in a two-dimensional view. view.The axis The of axis the of the columncolumn is 3.4 m is 3.4from m datum from datum A and A 2.1 and m 2.1from m datum from datum B. The B. tolerance The tolerance zone is zone perpendicular is perpendicular to the to the surfacesurface floor and floor is and located is located with basic with dimensions basic dimensions relative relative to datum to datum A and A datum and datum B on the B on sides. thesides. It is envisagedIt is envisaged that the that TOP the control TOP control in GD&TIC in GD&TIC is mainly is mainly used for used three for purposes: three purposes: (1) to control (1) to control the locationthe location of the of features the features of size of (e.g., size (e.g., column columnss and andbeams) beams) and and (2) to (2) control to control the the distance distance between between the the featuresfeatures of of size. size. When When the TOPTOP controlcontrol is is applied, applied, the the perfect perfect position position is defined is defined with basicwith dimensionsbasic dimensions to specify either the exact location of the axis of a feature of size or the location of a feature of size in relation to another feature of size or surface datum. Figure 13a shows six steel columns (related to Tolerance Problem 6), and Figure 14a shows ten beams in a roof (related to Tolerance Problem 5). The TOP control has been applied to these two examples. The tolerance zone and the perfect position of the controlled features are displayed in the figures. Figure 13b demonstrates how to control the location of a feature of size, and Figure 14b demonstrates how to control the distance between features of size.

(a) (b)

Figure 13. (a) TOP control applied to the columns; (b) demonstration of how to control the location of a feature of size.

Buildings 2020, 10, x FOR PEER REVIEW 17 of 33

(a) (b)

Figure 12. (a) Tolerance zone of the tolerance of position (TOP) control applied to a column; (b) position of the referenced column relative to datums.

Unlike orientation symbols, the location of the tolerance zone of the TOP control is established relative to a datum. Figure 12b shows the same column in a two-dimensional view. The axis of the column is 3.4 m from datum A and 2.1 m from datum B. The tolerance zone is perpendicular to the surface floor and is located with basic dimensions relative to datum A and datum B on the sides. BuildingsIt2020 is envisaged, 10, 62 that the TOP control in GD&TIC is mainly used for three purposes: (1) to 16control of 29 the location of the features of size (e.g., columns and beams) and (2) to control the distance between tothe specify features either of thesize. exact When location the TOP of the control axis of is a applied, feature of the size perfect or the position location ofis adefined feature with of size basic in relationdimensions to another to specify feature either of sizethe exact or surface location datum. of the axis of a feature of size or the location of a feature of sizeFigure in relation 13a shows to another six steel fe columnsature of size (related or surface to Tolerance datum. Problem 6), and Figure 14a shows ten Buildings 2020, 10, x FOR PEER REVIEW 17 of 32 beamsFigure in a roof 13a (relatedshows six to steel Tolerance columns Problem (related 5). to The Tolerance TOP control Problem has 6), been and applied Figure 14a to these shows two ten beams in a roof (related to Tolerance Problem 5). The TOP control has been applied to these two examples.examples. The tolerance zone zone and and the the perfect perfect position position of of the the controlled controlled features features are are displayed displayed in the in examples. The tolerance zone and the perfect position of the controlled features are displayed in the thefigures. figures. Figure Figure 13b 13 demonstratesb demonstrates how how to to control control the the location location of of a a feature feature of size, and and Figure Figure 14 14bb figures. Figure 13b demonstrates how to control the location of a feature of size, and Figure 14b demonstratesdemonstrates how how to to control control the the distance distance between between features features of of size. size. demonstrates how to control the distance between features of size.

(a) (b) (a) (b) Figure 13. (a) TOP control applied to the columns; (b) demonstration of how to control the location of FigureFigure 13. 13.( a(a)) TOP TOP control control applied applied to to the the columns; columns; ( b(b)) demonstration demonstration of of how how to to control control the the location location of of a feature of size. aa feature feature of of size. size.

(a) (b)

FigureFigure 14.14. ((aa)) TOPTOP controlcontrol appliedapplied toto thethe beams;beams; (b(b)) demonstration demonstration ofof howhow toto controlcontrol the the distance distance betweenbetween features features of of size. size.

FigureFigure 15 15 shows shows a a drawing drawing calloutcallout forfor thethe positionposition ofof columnscolumns (related(related toto ToleranceTolerance ProblemProblem 6).6). ‘15X’‘15X’ inserted inserted above above the the FCF FCF implies implies that that similar similar TOP TOPcontrol control is applied is applied to all the to columns. all the columns. The perfect The positionperfect position of the axis of ofthe the axis columns of the hascolumns been definedhas been using defined basic using dimensions. basic dimensions. A datum has A beendatum used, has namelybeen used, datum namely A, which datum is theA, which line behind is the theline columnsbehind the at thecolumns bottom. at the The bottom. feature The is the feature axis of is the the column,axis of andthe column the tolerance, and zonethe tolerance for the TOP zone control for the is cylindricalTOP control [104 is]. cylindrical Therefore, the[104] diameter. Therefore, symbol the mustdiameter be used symbol in the must FCF be just used before in the the FCF tolerance just before value the [95 tolerance]. value [95]. 4.2. Discrepancies between GD&TIC Rules and Some of the Commonly Used American and British Reference Documents

4.2.1. Shape of the Tolerance Zone for the Flatness Control Flatness in the British system is specified according to the service regularity, which is defined as deviation in height of the surface of a flooring layer over short distances in a local area [105]. With reference to the service regularity requirement, the suitability of a floor in service is determined by controlling changes in height over short distances. Flatness in the American system is the degree to which the surface approximates a plane. Hence, both definitions imply that flatness is determined over an area.

Figure 15. Drawing callout for the TOP control applied to the columns.

Buildings 2020, 10, x FOR PEER REVIEW 18 of 33

(a) (b)

Figure 14. (a) TOP control applied to the beams; (b) demonstration of how to control the distance between features of size.

Figure 15 shows a drawing callout for the position of columns (related to Tolerance Problem 6). ‘15X’ inserted above the FCF implies that similar TOP control is applied to all the columns. The perfect position of the axis of the columns has been defined using basic dimensions. A datum has been used, namely datum A, which is the line behind the columns at the bottom. The feature is the axisBuildings of the2020 ,column,10, 62 and the tolerance zone for the TOP control is cylindrical [104]. Therefore,17 ofthe 29 diameter symbol must be used in the FCF just before the tolerance value [95].

Buildings 2020, 10, x FOR PEER REVIEW 18 of 32

4.2. Discrepancies between GD&TIC Rules and Some of the Commonly Used American and British Reference Documents

4.2.1. Shape of the Tolerance Zone for the Flatness Control Flatness in the British system is specified according to the service regularity, which is defined as deviation in height of the surface of a flooring layer over short distances in a local area [105]. With reference to the service regularity requirement, the suitability of a floor in service is determined by controlling changes in height over short distances. Flatness in the American system is the degree to Figure 15. Drawing callout for the TOP control applied to the columns. which the surfaceFigure approximates 15. Drawing a plane. callout Henfor thece, TOP both control definitions applied imply to the thatcolumns. flatness is determined over an area. 4.2. DiscrepanciesIn practice, to between determine GD&TIC the flatness Rules and of concrete Some of andthe Commonly other types Used of finished American floors, and British the straightedge Reference In practice, to determine the flatness of concrete and other types of finished floors, the Documentsbasis is used in both American and British systems, especially for floors finished by conventional techniquesstraightedge [15 basis,35,105 is –used108]. in Figure both 16American shows the and principle British behindsystems, using especially a straightedge for floors to finished determine by conventional techniques [15,35,105–108]. Figure 16 shows the principle behind using a straightedge 4.2.1.the flatness Shape ofof floorthe Tolerance surfaces. TheZone straightedge for the Flatness is placed Control on the surface and will, therefore, be placed on theto determine two highest the points flatness along of its floor length. surfaces. The distance The straightedge (∆) between is the placed lowest on point the on surface the surface and will, and thetherefore, straightedgeFlatness be inplaced the is thenBritish on the measured system two highest is and specified must points be according along less that its to thelength. the permissible service The distance regularity, deviation (Δ) whichbetween for flatness. is definedthe lowest The as 2 deviationmpoint straightedge on thein height surface in the of andthe British surfacethe systemstraightedge of a [ 25flooring,33 ,is105 then laye] and measuredr over the 10 short ft straightedgeand distances must be in methodless a local that inarea the the [105].permissible American With referencesystemdeviation [15 to for,36 the ]flatness. are service currently The regularity 2 regardedm straightedge requirement, as standard in the the methods.British suitability system of [25,33,105] a floor in serviceand the is 10 determined ft straightedge by controllingmethod in thechanges American in heig systemht over [15,36] short aredistances. currently Flatness regarded in the as standardAmerican methods. system is the degree to which the surface approximates a plane. Hence, both definitions imply that flatness is determined over an area. In practice, to determine the flatness of concrete and other types of finished floors, the straightedge basis is used in both American and British systems, especially for floors finished by conventional techniques [15,35,105–108]. Figure 16 shows the principle behind using a straightedge to determine the flatness of floor surfaces. The straightedge is placed on the surface and will, therefore,Figure be placed 16. on the two highest points along its length. The distance (Δ) between the lowest Figure 16. The principle behind using straightedge to determine the flatnessflatness ofof floorfloor surfaces.surfaces. point on the surface and the straightedge is then measured and must be less that the permissible deviationThe definitionsfor flatness. of The the 2 flatness m straightedge control in in GD&TIC the British and system the flatness [25,33,105] in the aforementionedand the 10 ft straightedge standards The definitions of the flatness control in GD&TIC and the flatness in the aforementioned methoddo seem in tothe be American different system in nature. [15,36] The are usecurrently of the regarded straightedge as standard method methods. implies that there is a standards do seem to be different in nature. The use of the straightedge method implies that there is two-dimensional tolerance zone for flatness, whereas the tolerance zone for the flatness control should a two-dimensional tolerance zone for flatness, whereas the tolerance zone for the flatness control be three-dimensional. should be three-dimensional. 4.2.2. Shape of the Tolerance Zone for the TOP Control 4.2.2. Shape of the Tolerance Zone for the TOP Control The reviewed British reference documents, e.g., [34,37,109] and the reviewed American reference The reviewed British reference documents, e.g., [34,37,109] and the reviewed American reference documents, e.g., [32,36] for both concrete and steel elements assume a square tolerance zone for the perfectdocuments position., e.g., For[32,36] instance, for both Figure concrete 17a showsand steel a tolerance elements zone assume for aa columnsquare tolerance that is formed zone for by thethe perfect position. For instance, Figure 17a shows a tolerance zone for a column that is formed by the maximum and minimum of the horizontal and vertical location dimensions. The limits of 100 and 120 maximum and minimum of the horizontal and vertical location dimensions. The limits of 100 and mm at the bottom side and the left side of the column show the location of the column’s centre line. 120 mm at the bottom side and the left side of the column show the location of the column’s centre According to the reviewed American and British reference documents, which are based on coordinate line. According to the reviewed American and British reference documents, which are based on dimension, a square box is created around the centre as a tolerance zone. If the centre of the column coordinate dimension, a square box is created around the centre as a tolerance zone. If the centre of can deviate inside the tolerance zone, it will still be within tolerance. the column can deviate inside the tolerance zone, it will still be within tolerance.

Buildings 2020, 10, x FOR PEER REVIEW 19 of 33

Figure 16. The principle behind using straightedge to determine the flatness of floor surfaces.

The definitions of the flatness control in GD&TIC and the flatness in the aforementioned standards do seem to be different in nature. The use of the straightedge method implies that there is a two-dimensional tolerance zone for flatness, whereas the tolerance zone for the flatness control should be three-dimensional.

4.2.2. Shape of the Tolerance Zone for the TOP Control The reviewed British reference documents, e.g., [34,37,109] and the reviewed American reference documents, e.g., [32,36] for both concrete and steel elements assume a square tolerance zone for the perfect position. For instance, Figure 17a shows a tolerance zone for a column that is formed by the maximum and minimum of the horizontal and vertical location dimensions. The limits of 100 and 120 mm at the bottom side and the left side of the column show the location of the column’s centre line. According to the reviewed American and British reference documents, which are based on coordinate dimension, a square box is created around the centre as a tolerance zone. If the centre of Buildings 2020, 10, 62 18 of 29 the column can deviate inside the tolerance zone, it will still be within tolerance.

(a) (b) (c)

Figure 17. (a) The tolerance zone for a column when the position tolerance is applied based on the reference documents;documents; ( b()b the) the maximum maximum distance distance between between the axisthe ofax theis of column the column and the and target the location target inlocation the tolerance in the tolerance zone; (c) comparisonzone; (c) comparison between the between tolerance the zonetolerance for the zone position for the tolerance position implied tolerance by theimplied reference by the documents reference anddocuments GD&TIC. and GD&TIC.

However, asas explainedexplained earlier, earlier, the the tolerance tolerance zone zone in in GD&TIC GD&TIC for for the the TOP TOP control control is cylindrical.is cylindrical. In thisIn this case, case, it was it thewas authors’ the authors’ choice choice to propose to propose modifications modifications to the reference to the documents,reference documents, as opposed as to adoptingopposed to GD&TIC adopting in theGD&TIC referencing in the documents. referencing The documents. reasoning The behind reasoning this choice behind was this that choice the axis was of thethat column the axis can of the be o columnff the targeted can be locationoff the targeted in diagonal location directions, in diagonal which meansdirections, that which it will bemeans a greater that distanceit will be compareda greater distance with the compared vertical and with horizontal the vertical directions and horizontal (Figure directions 17b). In other(Figure words, 17b). In the other axis maywords, be the in theaxis corner may be at in a distancethe corner of at 14.14 a distance mm from of 14.14 the perfect mm from position; the perfect however, position; it would however, still be it withinwould tolerance.still be within It seems tolerance. illogical It seems to accept illogical only to this accept distance only and this not distance to accept and the not same to accept distance the insame any distance other direction. in any other It is moredirection. logical It is to more allow logical the same to allow tolerance the same of 14.14 tolerance mm for of the 14.14 axis mm of thefor columnthe axis inof allthe directions. column in The all tolerancedirections. zone The is tole diametricrance zone in a two-dimensionalis diametric in a two-dimensional view and is cylindrical view inand a three-dimensionalis cylindrical in a three-dimensional view (Figure 17c). view (Figure 17c). 2 In In Figure Figure 17 17a,b,c,a–c, the the tolerance tolerance zone zone is 20is 20 by by 20 20 mm. mm. This This leads leads to to a tolerancea tolerance area area of 400of 400 mm mm. If2. theIf the circle circle that that envelops envelops this this square square is considered is considered with thewith Pythagorean the Pythagorean theorem, theorem, the diameter the diameter equals 2 28.28equals mm. 28.28 Considering mm. Considering this diameter, this diameter, the tolerance the tolerance area will area be will 628.13 be 628.13 mm . Inmm other2. In words,other words, using theusing perfect the perfect position position with a with cylindrical a cylindrical tolerance tolerance zone allows zone allows for 57% for of 57% a larger of a tolerancelarger tolerance zone whilst zone providingwhilst providing the same the function. same function. In short, In GD&TIC short, GD&TIC will add 57%will moreadd 57% to a tolerancemore to a zone tolerance by considering zone by the cylindrical tolerance zone than the conventional coordinate systems used in the existing standards would allow.

4.3. Evaluation of GD&TIC

A summary of the discussions and comments made after each question during the focus group meeting is given next.

4.3.1. Efficacy GD&T is useful in the sense that “it decomposes tolerance information into three geometric categories” (Quotation 1). Dividing the tolerance information into distinct comprehensible categories ensures that “they are more easily communicated” (Quotation 2). Additionally, GD&TIC improves clarity and consistency in drawings, as “it provides the same use of language for parties in a project when communicating tolerance information” (Quotation 3). Following GD&T ensures that all parties “are aware of tolerance information” (Quotation 4).

4.3.2. Practicality GD&TIC is a “comprehensive tolerancing system” (Quotation 5), and, as a result, “its understanding is overwhelming” (Quotation 6). The comprehensiveness of GD&TIC “requires Buildings 2020, 10, 62 19 of 29 users for a great deal of training ... [and, therefore], makes it more complicated to learn” (Quotation 7). Moreover, “sustaining the implementation of GD&TIC throughout the project and motivating designers to follow all rules is another hindrance” (Quotation 8).

4.3.3. Acceptability “If the economic advantages are highlighted, then there is a higher chance that GD&TIC will be accepted” (Quotation 9) by designers and contractors. “yes, there is nothing that you have said today that we should not be doing as a standard tolerancing system. If we do not get [the work] right the first time, it costs us money” (Quotation 10). However, “terms and rules used in GD&TIC are difficult to understand for the industry” (Quotation 11). The participants recommended “tone down some of the academic language so it is in layman’s terms, [and then GD&TIC] would probably be more readily accepted” (Quotation 12).

4.3.4. Efficiency The participants acknowledged that “we need to be more concerned with tolerances, it is an issue across the industry” (Quotation 13). Tolerance problems are costly and “they may cost contractors remarkably more than avoiding them proactively” (Quotation 14). GD&TIC can potentially “reduce the rework” (Quotation 15) that is caused by tolerance problems through improving the communication of tolerance information. The reduction of rework often leads to “the elimination of waiting time incurred by the modification of tolerance problems” (Quotation 16). To answer this question, the costs of incorporating GD&TIC into the design process should have a sum deducted equivalent to “the cost of tolerance problems due to poor communication of tolerance information and the cost of waiting time” (Quotation 17). Further investigation is needed “to explore the amount of savings as a result of GD&TIC” (Quotation 18).

4.3.5. Applicability On the question related to the applicability of GD&TIC, the participants stated: “from the academic point of view, yes” (Quotation 19). However, in practice, “it requires all parties, from designers to operatives on site, [to] understand GD&TIC and its rules” (Quotation 20), which is “very difficult to achieve” (Quotation 21).

5. Discussion In this paper, the current practice of tolerancing in the AEC industry was reviewed. It was argued that some of the existing tolerancing methods do not specify the exact amount of permitted variations. Despite the simplicity of the conventional plus/minus system, types of geometric variations have not been grouped into widely known and documented categories in this system. In other words, the conventional tolerancing system is not able to systematically communicate geometric variation [110]. Hence, designers and practitioners in the industry are not systematically aware of different types of geometric categories and lack the vocabulary to communicate geometric variations [4,5,17,24,25]. For example, currently, the size dimension between two surfaces controls the parallelism, while in reality, size requirements do not specify the tolerance for parallelism requirements (Parallelism (Surface)). The first improvement to the conventional plus/minus system is that in GD&TIC, the geometric variations of a feature are grouped into three categories: (1) form, (2) orientation, and (3) location [17,19]. Given that GD&TIC is a dictionary of words that are symbols and concepts, a designer can choose the symbols that most appropriately convey tolerance information related to geometric variations [93]. It was acknowledged during the evaluation that dividing the tolerance types and geometric characteristics into distinct categories ensures that tolerance information is more easily communicated compared with conventional tolerancing methods in which such categorisation does not exist (Quotations 1,2, and 4). Additionally, the use of the same language among parties improves clarity and consistency in drawings (Quotation 3). Buildings 2020, 10, 62 20 of 29

Though the term ‘HOLD’ or the plus/minus sign can be used to distinguish between important and less important dimensions, designers cannot systematically specify the critical features (e.g., straightness, flatness, perpendicularity, parallelism, and position) on a component or in a sub-assembly. The second improvement to the conventional tolerancing system is that in GD&TIC, the feature control frame (FCF) helps to systematically communicate the permissible variation of critical features on a component or in a sub-assembly [4,5,17,24,25]. For example, Figure 11a illustrates how GD&TIC can communicate the perpendicularity tolerance of columns as a critical feature in an assembly. When using conventional tolerancing systems, designers do not systematically specify the relationship between critical features of the components in an assembly [8]. The third improvement to the conventional systems is that GD&TIC overcomes this challenge by establishing datum to locate other features [17,19,45]. For example, in Figure9a, the parallelism relationship between two walls separated by a door is established by the datum on one of the walls. The typical tolerancing system used in the AEC industry does not systematically define tolerance zones. There is only a general consensus that tolerance zones start from the lower limit and go to the upper limit when using the plus/minus system [111]. The fourth improvement to the conventional tolerancing systems is that GD&TIC has a precise definition for each of the tolerance zones of the form, orientation, and location tolerances. All the points of the features must be within the defined tolerance zones. The width of the tolerance zones is determined by tolerance values [46]. Given the call by organisations involved in developing AEC industry standards to improve existing tolerancing methods (Section 2.1), GD&TIC can potentially be considered as a tolerancing system for the industry. The knowledge transfer from manufacturing into AEC must be treated with caution, and differences between these two industries must be taken into account [112]. In this regard, two discrepancies between GD&TIC rules, and some of the commonly used American and British standards on tolerances were found (Section 4.2). It was argued that the shape of the tolerance zone for the flatness control is three-dimensional, whereas the existing reference documents imply that there is a two-dimensional tolerance zone for flatness (Section 4.2.1). Moreover, existing reference documents assume a square tolerance zone for the perfect position, whereas it was proven that the tolerance zone of the TOP control is cylindrical (Section 4.2.2). Note that although the scope of this research was to identify discrepancies of GD&TIC rules with American and British reference documents, there is not any limitation to adopt GD&TIC in AEC projects of any country. Table6 summaries the proposed application of each geometric characteristic in AEC.

Table 6. A summary of the proposed applications of each geometric characteristic in GD&TIC.

Type of Tolerance Geometric Characteristics Applications Straightness To control the beams and columns that are prone to deformation. Form Flatness To control the flatness of floor surfaces. To control components for which plumbness tolerances are a Perpendicularity (surface) Orientation major concern. Parallelism To control surfaces that should maintain a constant distance. To control (1) the location of features of size such as columns and Location Tolerance of Position (TOP) beams and (2) the distance between those features of size

During the focus group meeting conducted to evaluate GD&TIC, it was discussed that GD&TIC is expected to eliminate the rework caused by tolerance problems, including those encountered in Case A and Case B (Quotation 19), through the improvement of the communication of tolerance information (Quotation 15). The elimination of rework is a basic element of the reduction of processing time [113]. However, further investigation is required to understand whether the costs of incorporating GD&TIC into the design process outweigh the costs saved through the improved tolerancing (Quotations 17 and 18). If the economic advantages of GD&TIC can be demonstrated, then there is a higher chance that it will be accepted and used in the industry (Quotations 9 and 10). It was acknowledged that GD&TIC is a comprehensive tolerancing system (Quotation 5) and therefore that its understanding is overwhelming (Quotation 6). The difficulties in learning terms and rules used in GD&TIC and in Buildings 2020, 10, 62 21 of 29 motivating designers to sustain the implementation of GD&TIC throughout the project were raised as the major hindrances to the acceptance and practicality of this tolerancing system (Quotations 7, 8, 11, 12, 20, and 21). This situation is similar to when GD&T was introduced to manufacturing [17]. Organisations developing AEC reference documents, BIM, and training courses can play major roles to overcome the hindrance of widely implementing GD&TIC in AEC. It is suggested that organisations involved in developing AEC industry reference documents start reviewing and harmonising the existing terminology and replacing them with categories and tolerance characteristics used in GD&TIC. The out of date conventional tolerancing systems in current reference documents can also be updated with GD&TIC. Moreover, parametric modelling in BIM enables objects to receive GD&TIC symbols and rules to bridge the gap between design and construction. In particular, the concept of datum can be embedded in objects and the relationship between the critical features of objects can be described with tolerance characteristics. Designers can then systematically incorporate tolerances into building information models, and such models become the main tool for the communication of tolerance information. Regarding training courses, their purpose is to provide architecture and engineering students with an overview of terminology used in GD&TIC and to apply GD&TIC in a design setting.

6. Conclusions The aim of this research was to prescribe the application of GD&T in construction to improve communication of tolerance information in AEC drawings. In this paper, an overview of the existing practice of tolerancing in the AEC industry was presented. It was discussed whether the lack of a standardised approach for tolerancing leads to ambiguous situations during design and to tolerance problems during construction. Despite the potentially sever consequences of those tolerance problems, the literature has mostly focused on exploring the problem with tolerancing rather than proposing a solution to improve it. Design science research (DSR) was chosen as the methodological approach because its focus is on prescribing a solution to solve a practical problem (e.g., a poor communication of tolerance information), as well as on contributing to theory. DSR in this research consisted of four steps, namely ‘problem definition’, ‘problem awareness’, ‘development’, and ‘evaluation’. The ‘problem definition’ step helped to recognise the areas of concern for tolerancing in AEC from the preceding researchers’ point of view. In the ‘problem awareness’ step, six tolerance problems caused by poor communication of tolerance information were identified in two construction projects. Direct observations and two group interviews were used to collate data in this step. Next, the proposed solution, GD&TIC, was developed based upon the configuration of understanding gained during the literature review and through the analysis of the identified tolerance problems. The terms and rules of GD&TIC and its differences, compared with some of the commonly used American and British reference documents on tolerances, were established. The preliminary version of GD&TIC consists of five geometric characteristic symbols that fall into three categories, namely form, orientation, and location. The remaining nine symbols were deemed to be less applicable and could be controlled by other symbols; therefore, they were excluded from GD&TIC. This research prescribed how tolerance information in drawings is specified through a feature control frame (FCF) by which geometric tolerances are applied to components and sub-assemblies. Two compartments of FCF are datum and tolerance zone. The datum is a theoretically exact axis or plane from which the location or geometric characteristics of a feature are established. The tolerance zone is a two- or three-dimensional area within which all the toleranced features must be contained. The application of GD&TIC was delineated through examples related to the identified tolerance problems. Though GD&T is widely used in manufacturing, none of its categories and symbols have been deployed in the AEC industry thus far for the purpose of communicating tolerance information. The existing tolerancing approaches are only able to communicate dimensional variations and do not communicate geometric variations by grouping them into distinct categories and characteristics. In other words, the Buildings 2020, 10, 62 22 of 29 deployment of GD&T in construction is currently missing in the literature and is a novel contribution to theory. Eventually, a focus group meeting was conducted to evaluate GD&TIC based on five attributes set out in the developed framework. The attributes were acceptability, efficacy, efficiency, practicality, and applicability. The weak and strong criteria of the UA requirements of the method were followed to ensure that a realistic environment for the implementation of GD&TIC was approximated. It was acknowledged during the ‘evaluation’ step that GD&TIC is potentially capable of improving tolerancing and reducing tolerance problems caused by poor communication of tolerance information. This is to reduce the remedial actions needed to solve tolerance problems during construction. Therefore, this research contributes to practice because it demonstrates a solution for practitioners seeking to improve tolerancing and to reduce the number of tolerance problems. However, according to the participants in the focus group, it is difficult to learn terms and rules used in GD&TIC, as well as to motivate designers to sustain the implementation of GD&TIC throughout projects. These difficulties were acknowledged as the major barriers to the acceptance and practicality of GD&TIC in industry. Future works of this research include: (1) the further development of GD&TIC rules and concepts, (2) the incorporation of GD&TIC in building information models, (3) providing a guideline to facilitate the implementation of GD&TIC.

Author Contributions: Conceptualization, S.T., L.K., P.T.; formal analysis, S.T.; methodology, S.T., M.K., P.T., L.K.; validation S.T., P.T., L.K., visualization, S.T.; supervision, L.K., P.T.; writing—original draft preparation, S.T.; writing—review and editing, S.T., L.K., P.T., M.K., A.K. All authors have read and agreed to the published version of the manuscript. Funding: This research is funded by the Innovative Design Lab, School of Art, Design and Architecture, University of Huddersfield. Conflicts of Interest: The authors declare no conflict of interest.

Appendix A. Summary of Identified Tolerance Problems in Case A and Case B. The tolerance problems identified in Case A and Case B and the reason behind their occurrence are explained in Table A1. Buildings 2020, 10, 62 23 of 29

Buildings 2020, 10, x FOR PEER REVIEW 24 of 32 Buildings 2020, 10, x FOR PEER REVIEW 24 of 32

Table A1. Summary and illustrationTableTable of A1 A1 the. .Summary Summary tolerance and and illustration illustration problems of of the the tolerance tolerance identified problems problems in identified identified Cases in in ACasesCases and A A and and B. B. B.

Tolerance No. Tolerance ProblemNo. Tolerance DescriptionDescription Illustration No. problem Description Illustration problem Case A CaseCase A A The deflection calculationTheThe deflection deflection in thiscalculation calculation project in wasin this this based project project on was was slab ba ba pouredsedsed on on slab slab to thepoured poured constant to to the the thicknessconstant constant thickness thickness specified, and nospecified, account and had no been account taken had for been any taken additional for any weight additional as a weight result ofas thea result deflection of the deflection of of specified, and no account had been taken for any additional weight as a result of the deflection of Excessive gap between the the supporting structure.thethe supporting supporting However, structure. structure. more However, However, concrete more more was concrete concrete poured was was to level poured poured the to to concrete level level the the slab concrete concrete and slab slab and and Excessive gap between the achieve the intendedachieve flatness the intended tolerance flatness ( 5 to mm)lerance to a (±5 certain mm) extent.to a certain Making extent. the Making slab thicker the slab thicker skirtingskirting and and concrete concrete slab slab achieve the intended flatness± tolerance (±5 mm) to a certain extent. Making the slab thicker overloaded the ceiling,overloaded and the this ceiling, eventually and this caused eventually more ca deflectionused more (30deflection mm more (30 mm than more the than the Flatness of overloaded the ceiling, and this eventually caused more deflection (30 mm more than the 1 Flatness of concrete slab 1 specifiedFlatness tolerance).of specified As a tolerance). result, the As intended a result, flatnessthe intended could flatness not be could achieved. not be Anachieved. excessive An excessive gap gap 1 concrete slab specified tolerance). As a result, the intended flatness could not be achieved. An excessive gap concretewas observed slab betweenwas observed the concrete between slab the andconcrete recessed slab and skirting. recessed This skirting. tolerance This problemtolerance (theproblem (the was observed between the concrete slab and recessed skirting. This tolerance problem (the excessive deflectionexcessiveexcessive of the deflection deflection concrete of of slab the the andconcrete concrete the subsequentslab slab and and the the subsequent gapsubsequent between gap gap the between between slab and the the recessedslab slab and and recessed recessed skirting) occurredskirting)skirting) because occurred occurred of the because lackbecause of communicationof of the the lack lack of of commu commu betweennicationnication the between between structural the the structural designer,structural designer, thedesigner, the the architect, and thearchitect,architect, concrete and and contractor the the concrete concrete regarding contractor contractor the regarding regarding anticipated the the anticipated deflectionanticipated anddeflection deflection required and and flatnessrequired required flatness flatness tolerances. tolerances.tolerances.

The cladding contractor developed a design in which the offset from the steelwork to the face of The cladding contractorThe cladding developed contractor a design developed in which a design the in off whicset fromh the theoffset steelwork from the tosteelwork the face to of the face of the stone panelsthethe was stone stone 272 panels mm.panels Inwas was that 272 272 case, mm. mm. theIn In that that cladding case, case, the the system cladding cladding could system system absorb could could 32 absorb mmabsorb of 32 32 mm mm of of deviations due todeviationsdeviations the inclination due due to to the ofthe steelinclination inclination columns of of steel steel and column column stone panels.ss and and stone stone The panels. panels. architect The The later architect architect increased later later increased increased PerpendicularityPerpendicularitythe offset to 290the mm.the offset offset This to to was 290 290 mm. tomm. accommodate This This was was to to accommodate accommodate the installation the the installation betweeninstallation the between between steelwork the the steelwork steelwork and and and ofof columnscladding. columns and and Given cladding.cladding. that the distanceGiven Given that that between the the distance distance the steelworkbetween between the the and steelwork steelwork cladding and and system cladding cladding increased, system system increased, increased, the the the Perpendicularity of columns and stone 2 22 stonestonebrackets panels panels of of theof claddingbracketsbrackets of systemof the the cladding cladding could onlysystem system absorb could could 15only only mm absorb absorb deviations. 15 15 mm mm deviations. deviations. As the stone As As panelsthethe stone stone were panels panels were were panels of the cladding system thethebeing cladding cladding installed, thebeingbeing steel installed, installed, columns the the and,steelsteel columns subsequently,columns and, and, subsequent subsequent the stonely,ly, panels the the stone stone started panels panels to leanstarted started into to to lean thelean into into the the buildingsystemsystem up to 30buildingbuilding mm at up theup to to roof 30 30 mm mm level. at at the Thisthe roof roof problem level. level. This This occurred prob problemlem due occurred occurred to the lackdue due to ofto the communicationthe lack lack of of communication communication between the structuralbetweenbetween designer, the the structural structural the architect,designer, designer, the andthe architect, architect, the cladding and and the the contractor cladding cladding aboutcontractor contractor the about anticipatedabout the the anticipated anticipated perpendicularityperpendicularityperpendicularity variations of columns variatio variations andns of of columns thecolumns required and and the perpendicularitythe required required perpendicularity perpendicularity tolerance oftolerancetolerance columns of of columns columns Excessive perpendicularity variations and stone panels. Excessive perpendicularity variations and stone panels.and stone panels. of columns and stone panels Buildings 2020, 10, x FOR PEER REVIEW 25 of 32 of columns and stone panels

Excessive gap between the channel and the stone panels

When the deadWhen load, duethe dead to the load, cladding, due to wasthe cladding, applied onwas the app steellied frame,on the steel the stoneframe, panels the stone started panels started to sag. There was a noticeable gap between the channel and the stone panels in some areas, and to sag. There was a noticeable gap between the channel and the stone panels in some areas, and Straightnessthe gap was of notthe consistent gap was all not the consistent way through. all the way This through. problem Th (theis problem excessive (the deflectionexcessive deflection of steel of steel 3 Straightness of beams 3 beamsbeams and the subsequentbeams and the gap subsequent in the cladding) gap in the was cladding) as a result was of as the a result lack of the communication lack of communication of of the straightnessthe tolerances straightness of the tolerances beams betweenof the beams the between structural the engineer, structural the engineer, architect, the architect, and the and the cladding contractor.cladding contractor.

Case B

Columns, parallel flange channels (PFCs), and cladding rails were misaligned for 30–40 mm, so it was not possible to fit the roller shutter doors without the adjustment of the columns and PFCs. Parallelism of 4 This problem occurred because no information could be found to indicate that the parallelism of the doorways stanchions was essential to ensure that electrically operated shutter doors would fit in the doorways.

Misalignment of stanchions

Buildings 2020, 10, x FOR PEER REVIEW 25 of 32

Excessive gap between the channel and the stone panels

When the dead load, due to the cladding, was applied on the steel frame, the stone panels started to sag. There was a noticeable gap between the channel and the stone panels in some areas, and Straightness of the gap was not consistent all the way through. This problem (the excessive deflection of steel 3 Buildings 2020, 10, 62 beams beams and the subsequent gap in the cladding) was as a result of the lack of communication of 24 of 29 the straightness tolerances of the beams between the structural engineer, the architect, and the cladding contractor. Table A1. Cont.

No. Tolerance Problem Description Illustration Case B Case B

Columns, parallelColumns, flange channelsparallel flange (PFCs), channels and cladding (PFCs), and rails cladding were misaligned rails were misaligned for 30–40mm, for 30–40 so it mm, so it was not possiblewas to fitnot the possible roller to shutter fit the doorsroller shutter without doors the wi adjustmentthout the adjustment of the columns of the andcolumns PFCs. and PFCs. Parallelism of 4 Parallelism of the doorways 4 This problem occurredThis problem because occurred no information because no could information be found could to be indicate found thatto indicate the parallelism that the parallelism of of the doorways stanchions was essentialstanchions to was ensure essential that to electrically ensure that operated electrically shutter operated doors shutter would doors fit would in the fit in the doorways. doorways.

Misalignment of stanchions

Buildings 2020, 10, x FOR PEER REVIEW 26 of 32 Buildings 2020, 10, x FOR PEER REVIEW 26 of 32

The purlins on theThe roof purlins that on support the roof the that cladding support panelsthe cladding were panels out of were the correct out of the positions correct positions for 20 for 20 Position of mm. As a result,mm. there As were a result, no fixingthere were points no forfixing the points panels. for Thisthe panels. problem This occurred problem dueoccurred to the due to the 5 Position of purlins on the roof 5 purlins on the lack of communicationlack of communication between the steel between and claddingthe steel and contractors cladding contractors about the requiredabout the positionrequired position roof tolerance of purlins.tolerance of purlins.

The purlins were out of the correct positions for 20 mm

The building was erected in two sides; hence, there was an interface between these two sides of The building wasThe erected building in twowas erected sides; hence, in two theresides; washence, an th interfaceere was an between interface these between two these sides two of sides of the structure. It turned out that most of the columns in the first side were out of the position Positionthe structure. of It turnedthe structure. out that It turned most ofout the that columns most of the in thecolumns first side in the were first outside of were the out position of the position 6 Position of between 10–15 mm towards the second side. As a result, the beam coming across the top and 6 Position of columns 6 betweencolumns 10–15 mmbetween towards 10–15 the mm second towards side. the Assecond a result, side. theAs a beam result, coming the beam across coming the across top and the top and columns connecting two sides of the building could not be fitted. This problem occurred because the connecting two sidesconnecting of the two building sides of could the building not be could fitted. not This be problemfitted. This occurred problem becauseoccurred thebecause the position tolerance of columns was not communicated to the steel contractor. position toleranceposition of columns tolerance was of columns not communicated was not communicated to the steel to contractor. the steel contractor.

Lack of fit of the beam

Buildings 2020, 10, 62 25 of 29

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