CERTIFICATE Iv BUILDING CONSTRUCTION

CERTIFICATE IV BUILDING CONSTRUCTION Training Package BCG03

BCGCB4007A Plan Building or Construction Work

TAFE NSW Riverina Institute, Albury Campus Overview

Most building company’s today use a computerised Construction Project Management System. This allows them to schedule tasks efficiently, manage resources, monitor costs and report on projects for analysis and presentation i.e. the detailed work schedule is prepared using computerised Construction Project Management software.

In planning the programme for a construction project, it is necessary to know all distinct operations of the project. How they would be done, who will do them, and in what sequence they can be carried out. Working times will then be determined for the various operations and each operation will be fitted into a “builders’ calendar” period over which the contract will be completed.

The builder will approach the scheduling work on the “KEY DATE TABULATION PRINCIPLE”. Under this method they will establish starting and finishing dates for the basic elements of the work, eg. preliminaries, soil and water management, bulk excavations, retaining walls, concrete piers, footing and pads, brickwork, internal sewer drainage, cast in- situ concrete floors, wall frames, roof frames, insulation and roofing work and so on.

Detailed operations will be then fitted into this overall plan, keeping in mind the necessary sequences. The construction programme is aimed for effective co-ordination of activities, therefore congestion and interference will be kept to a minimum. The schedules needed constant revision and updating during the contract period, and preplanning provides the means of meeting these changes.

GANTT OR BAR CHARTS

In the early 1900’s, Henry 1. Gantt and Frederick W. Taylor’ realised that effective planning had a dramatic impetus within the manufacturing industry. They developed a graphical method of producing a time/task schedule which was adopted by the industries of the time and is today used widely. The GANT or BAR CHART is often seen. A sample of a simple Gantt Chart is shown below:

2 Some of the advantages and disadvantages of this type of schedule are as follows:

Advantages • Simple and easy to produce. • Easily read and understood by unskilled personnel • Progress can be recorded and shown visually • Can be easily adjusted to suit altered circumstances • Schedules of event dates can be easily produced from the information • Milestone events can be shown on the chart • Dates for ordering of materials, issuing notices, deliveries of materials and equipment can all be shown on the chart and easily seen • Supplementary short term program can be easily integrated with the main chart • Simple personnel resource profiling and cash flows can be produced from the chart • Suitable technique for small projects

Disadvantages • Complex critical links between inter-related tasks do not show clearly • Critical tasks are not always considered when the chart is produced

3 • Charts tend to be static representations of situation and do not show true dynamic inter-relationships of activities

A typical bar chart should include, as well as the expected start, duration and completion of an activity, a method of keeping control of or monitoring progress. This may be done in a number of ways:

 colouring in the bars  drawing parallel bars  coloured pins (for a wall chart)

The actual bar chart has no specific design but any method used should contain as a minimum:

• project name • timescale (daily, weekly, etc) • dates • activity description (in order of appearance on site) • dependencies, activity to activity (this is not always appropriate or easy to show on a bar chart and can get quite cluttered, so is usually only shown for simple projects). However, the time that an activity bar is started is dictated by any dependencies. • a moving day/date cursor for showing time elapsed • a method of recording progress • completion date (target and/or contract)

Bar charts are drawn with the activities listed in a column on the left-hand side of the page, and the time shown horizontally. Work periods or times to complete each activity are shown with ‘bars’ which may be open or coloured in, according to what they represent. Often, the bar charts are coloured in as the job progresses, to show the proportion of work completed at a particular point in time.

Some points to note:

• Actual dates appear at the top of the chart, so it is easy to look down and see which activities should be complete, which are in progress and which are due to start on any particular day. • The length of the ‘bar’ for an activity indicates the length of time required for its completion. It is possible therefore to monitor

4 activities as to whether they are ‘on track’, ahead of schedule or behind schedule. Appropriate action could be taken then to get the project back on track • it is possible to show dependencies between activities by drawing an arrow from the end of one down to the start of another. However, on a large project, this can become very cluttered, so a bar chart is often not the best way to show dependencies.

The Construction Project is broken into tasks and then the task is divided into phases or steps. Here is an example of “Preliminaries”:

Preliminaries:

• Assign a full time Project Manager / Site Supervisor. • Send suppliers & subcontractors tender packages including your company’s “Terms of Engagement”. • Examine quotations received from suppliers & subcontractors • ‘Signing trade contracts (SC2), to successful suppliers / subcontractors clearly specify contractual conditions & terms of engagement • Work Cover Notice of Intention to Commence Construction Work / submit notice. • Surveyor to check existing levels and contours indicated on the site drawings • Setting out work • Obtain Survey Set-out Certificate

Objectives

The objective of using a project management system for a construction project is to assess the features of the project before it is begun. It should enable the project to run as smoothly as possible based on a predicted sequence of events and activities that has been carefully compiled and analysed. The construction programme allows the builder to: • co-ordinate project activities, • predict purchasing requirements, • arrange for timely delivery of materials, • plan for efficient use of resources, • predict cash flow for the duration of the project,

5 • monitor costs, • monitor performance, • monitor overall progress.

These management functions that are undertaken by the builder are organisational issues that are made easier by having a construction programme.

The builder can also use the ability to monitor costs and progress on various aspects of the project to control the overall progress, and make allowances or changes as necessary. There are various methods of planning but to ensure useability, a construction programme needs to be • easy to interpret, • easy to change (flexible), • accurate, and • have input from all involved parties, as well as • show all required, relevant information.

Construction activities and sequence

In order to be able to generate a construction programme, it is necessary to be able to identify activities and to understand the relationship between the activities. This will generally require some experience of construction techniques and also of all of the tasks involved in a project from site establishment to completion and handover.

It is also important to be able to assess the level to which the job needs to be broken down. Too detailed a list of activities can make the planning process too time consuming and of no additional use in the management of the job. Conversely, too little detail will not allow the job to be managed efficiently. A large project with an unwieldy number of activities can be planned at different levels.

The overall job can be planned to allow an overview and general monitoring, and selected components of the job can be planned and analysed in more detail as a sub-plan. This sub-plan can be consulted only as required but can also serve as the main planning tool that is used by the supervisor of that section of the work.

6 Let us look at an example of a construction activity sequence for a basic brick veneer cottage.

Sample construction activities list

I. Clear and establish site 2. Arrange temporary services; electricity, water, etc 3. Arrange sub-contractors and approximate dates 4. Arrange materials and approximate delivery dates 5. Set out 6. Bulk and detailed excavation for footings 7. Plumber to install pipes and drains 8. Formwork to ground slab 9. Vapour barrier/Termite treatment 10 Notice to council for inspection 11. Fix reinforcement 12. Place and finish concrete to slab 13. Cure slab 14. Erect wall frames 15. Arrange for inspection 1 6. Erect roof trusses 17. Install windows and external door frames 18. Roof plumbing 19. Attach roof covering 20. Construct external walls (brick veneer) 21. Install external doors, decking and steps 22. Electrical rough-in 23. Plumbing rough-in 24. Brick cleaning 25. Wet area waterproofing 26. Install wall insulation 27. Fix internal linings 28. Joinery and fit-out 29. Wall and floor tiling 30. Painting 31. Plumber final fit-out 32. Electrician final fit-out 33. Install ceiling insulation 34. Complete landscaping and erect fences

Notice that the list is in the order in which the activities need to occur. It allows for a break up of activities where trades are required on

7 more than one occasion, eg electrical, for the initial wiring, and then later, after the internal linings and finishes have been installed, for the final fix eg power points, switches, light fittings, etc. In addition, an attempt has been made to be inclusive of all activities. Omitting an activity could be disastrous for the progress of the project.

Given a drawing of a medium sized project, you need to be able to identify the key activities and to list them in rough order such as has been done above. You might have more or fewer activities or different names, you might combine some of the activities into one activity, or you might have some activities that do not appear above that are particular to your project. With experience, you will find the ‘name’ and ‘extent’ of the activities that suits you best. But remember that for a given size of project, there will be a certain number of activities that will be reasonable, being neither too scant nor too unwieldy to be useful. And try not to forget anything that could be critical!

Activity I

Using the construction activity list above as a guide, and your knowledge of construction from your other subjects, study the drawing below and list the main activities involved in the building of this structure.

Put your list of activities in a table and estimate a time you think it might take to complete each of your activities. Add this to your table as a ‘duration’ column.

8 9 Activity no. Description Duration (days) 1 2 3 4 5 6 7 8 9 10

You will realise when you read through a list of activities for a construction project, that they do not have to happen one after the other in a consecutive sequence.

Some activities must be completed before others are begun, but many can occur simultaneously or can begin before a previous one is finished. This relationship between activities is called ‘dependency’. Dependency defines what activities must be complete before others can begin. For example, before wall frames can be erected, the slab must have been poured and cured. However, waterproofing of wet areas could be happening at the same time as the electrical rough-in.

This information is added to a list of the construction activities by noting the number of the activity(s) that must precede a given activity, in a separate column.

See our example below from our previous list of construction activities:

10 Activity Duration Description Dependency (days) no. 1 Clear and establish site 2 none Arrange temporary 2 services; electricity, water. I none etc Arrange sub-contractors 3 I none and approximate dates Arrange materials and 4 2 3 approximate delivery dates 5 Setout I 4 Bulk and detailed 6 1 5 excavation for footings Plumber to install pipes and 7 2 6 drains 8 Formwork to ground slab 1 7 22 Electrical rough-in 2 19,20 23 Plumbing rough—in 1 20 24 Brick cleaning 1 20 etc

So, from the table above, it can be seen that activity no. 6, “bulk and detailed excavation for footings”, is dependent on the completion of activity no.5, “set out”. Also, activities 22, 23 and 24 all depend on the completion of activity 20, so can be occurring simultaneously. This information, compiled for an entire project, can be used to graphically represent the construction sequence or programme for that project. A graphical representation of this information can help to analyze the whole project in terms of what activities can be happening simultaneously and what the total duration of the project will be.

11 Note that the dependency column could be completed before the durations are estimated, but for the purposes of completing a network diagram which we will be doing later, the duration is not initially required.

Activity 2

Using the list of activities from your Activity I exercise, construct a table that includes the dependencies.

Activity no. Description Duration (days) Dependency 1 2 3 4 D 6 7 8 9 10

A note on duration of activities

Determining the duration of an activity is not as straightforward as it may seem. We need to consider the amount of work that need’s to be done, any time constraints on that work, and how many resources we have available to commit to the activity. Constraints might include, for example, having to pour sections of a large slab at specific intervals to allow for shrinkage, allowing for curing time of concrete, and allowing for cranage of structural items directly into position, with other demands on crane time.

Let’s consider an activity for which it has been estimated 160 hours

12 of carpentry work are required for it to be completed. Note that this is the amount of work, not the time it will take to complete. The time it will take to complete the work is dependent on the resources that are made available to do the work. In this example, if 2 carpenters were allocated to the 160 hours of work, and each worked an 8 hour day, the time taken to complete the work would be: 160 hours of work =10 days 2 carpenters for 8 hours ea

Therefore, activity duration is represented by the amount of work divided by the available resource to do the work. And for the planner who is considering activity durations, the available resource is a prime determinant. So you can see that the available resources are crucial to determining durations and this information should be available to the planner. The network diagram can be used to check allocations of resources and to ascertain over-allocation of resources, where durations have been determined using limited resources that have been. ‘doubly booked’ so to speak. It can also be used to re-allocate under utilised resources to other areas, see resource levelling later in this section.

Basic steps in compiling a bar chart

Lets go through the process of compiling a bar chart in steps:

1. List all the activities or operations to complete the job. An activity can consume time but not take any resources; for example, curing concrete could involve leaving a hose dripping onto a wet bag but the delay in the progress is a couple of days. Each activity has its own horizontal line indicating the length of time required for that activity. The order in which the activities are listed is not important but it does make it easier to draw the chart if they are listed in approximate chronological order.

2. For each activity, list any restraints, for example other activities that must immediately precede this particular activity. In situations where one activity may start part-way through the preceding activity, for example start painting already fabricated steel work before all fabrication is complete, then each activity may be broken into two or more activities. We could have an

13 activity such as: ‘fabricate first part of the steelwork’, followed by both activities of ‘paint the first part of the steelwork’ and ‘fabricate the second part of the steelwork’; this being followed by ‘paint the second part of the steelwork’. Note that in more sophisticated construction programming methods, such as using programming software, a ‘lag time’ or ‘delay’ can be put onto the start of an activity to account for this kind of situation where two activities can occur simultaneously, but one must be underway before the other can commence.

3. Estimate the duration of each activity — how long you think it would take to complete this activity — and enter this data.

4. Establish the project completion date. Draw the planning chart with each activity represented by a horizontal line of length equal to its duration and following restraining activities. Now it’s time for you to have a go. Try the following activity.

Activity 3

On the blank chart provided on the next page, complete a bar chart using the following information:

Level site This starts at zero and takes 2 days. This starts when level site is completed and the Set out garage duration is half a day. Excavate This starts also after set out is completed and drainage trench takes 2 days. Excavate Can begin after set out, requiring half a day to electrical trench complete. Can begin once set out of garage is completed. Excavate footings Requires 3 days. Duration of 2 days, after excavation of drain Lay drains trench is complete. One day duration. Can begin on completion of Lay conduits excavate electrical trench. Trench mesh can be placed once the footings Place trench have been excavated. This requires 3 days to mesh complete.

14 Inspect drains After drains have been laid. Requires 3 days. and backfill Inspect electrical After conduits are laid, electrical trenches can and backfill be inspected and backfilled, taking 2 days. This starts once backfilling of trenches is Slab preparation complete. Two days duration. Pour slab and when stab preparation is complete, slab can be cure poured. Pouring and curing requires 5 days.

Show all of the dependencies using an arrow to join the end of one activity to the beginning of another, as shown in the previous figure. For example, inspect electrical and back/ill cannot be started until the conduits have been laid. So the arrow for the activity inspect electrical and hack/Ill will follow from the end of the lay conduits activity.

15 http://www.youtube.com/watch?v=CW_wGSFavTc The sum of the individual activity durations is 26 days. What is the actual duration of the project, given that some of the activities can happen simultaneously?

You will notice that some activities may be started at a later time than indicated in the schedule, without affecting the duration of the job. This ‘extra time’ that is available for these activities are called ‘float’. For example, inspection and backfilling of electrical conduits can be delayed by 3 days without affecting the overall project. We say that it has a ‘float’ of 3 days.

It is very useful to have this time as it allows various resources to be allocated elsewhere, allowing more efficient programming of plant and personnel. However the amount of float is difficult to assess on a bar chart even when all of the dependencies are indicated. Float is most easily assessed using a tool called a network diagram, which we will discuss next.

When an activity does not have any float, that is, if the project duration will be increased if its start is delayed, then that activity is designated a critical activity, or an activity that is on the critical path.

For example, if backfilling of the drainage trenches is delayed, then the slab preparation will be delayed, which will delay pouring of the slab, and so the finish of the whole project will be delayed.

The critical path consists of those activities that determine the duration of the job, because any delay to the start of one of these

16 activities will delay the completion time of the job. The most convenient way of establishing the critical path is by constructing a network diagram.

CRITICAL PATH TECHNIQUES

In the late 1950’s E. I. du Pont de Nemours Company in the USA developed Network Analysis and the Critical Path Method ( C.P.M. ) of scheduling. The method was developed by du Ponts to assist them in their planning of the shut downs of their chemical plants for routine maintenance. Du Ponts developed a graphical network diagram which showed that every project has at least one sequence of events (or tasks ) that is critical to the completion of the overall project. By allocating each event an estimated time duration they were able, by simple mathematical calculations, to determine the minimum length of time that the project would take to complete. By utilising this method of scheduling du Ponts were able to save considerable time in their maintenance programs.

At about the same time, the United States Navy were developing a method of scheduling called Program Evaluation Review Technique (P.E.R.T.). They utilised this method of scheduling to manage the development of the Fleet Ballistic Missile Weapons System. This system was also based on the development of a logical network diagram. However, the times allocated for each event were calculated mathematically using standard statistical Beta and Normal Distribution Curves which were used to analyse each events times, using the most pessimistic, most optimistic and most likely predictions. By carrying out these calculations they were able to allocate the most likely time that each task would take. Utilisation of this method of scheduling meant the US Navy were able to plan and control the more than 2000 subcontractors involved in the development of the Polaris Missile system, achieving completion of the project ahead of time. A sample of a simple Network Diagram is shown below:

17 An example of a CPM network diagram showing Precedent Events layout

Reference to the above diagram shows a network which does not represent in any way a pictorial view of a project plan. The network diagram does not have any clearly identified time chart and the flow of the work tasks is hard to understand.

However, the information contained in the network is logical and the inter-relations between the tasks allows both sequential and parallel activities to be logically inter woven to illustrate the total configuration of events.

Some of the advantaged and disadvantages of this type of schedule are as follows:

Advantages:

• Separation of the planning process from the schedule preparation

• Times for activities are not considered in the development of the network diagram. Sequence of activities are the initial criteria for the network development. • The inter-relationships of all tasks is clearly shown on the network. This means that it can be clearly seen which activities are reliant on other activities. • Information from the network can be mathematically presented and used for the presentation of a graphical chart for the work. • Modem computer programs are available to carry out the development of the network plan and associated schedule.

18 Disadvantages:

• Development of network diagrams require high skill levels • Network diagrams are unwieldy and difficult to follow • Initial time required to develop the network diagram and associated schedule is high. • The cost required to prepare the initial schedule and to continue to maintain its correctness throughout the project is high.

Information

Information must also be considered as a required resource to allow the work to proceed. During the progress of the work certain information will need to be obtained to allow the work to proceed in a timely manner. The type of information that is required is as follows: • Engineering information required due to found conditions. • Colour schedules. • Special finishes schedules. • Selection of materials to be purchased under P.C. arrangements. • Any other information that needs to be supplied to the contractor during the progress of the work.

RESOURCE PLANNING & LEVELLING

Planning

Before the planner can commence the preparation of the schedule for a project, decisions will need to be made in regards to all resources. As stated previously, it can be seen that resource does not only include personnel but materials and plant/equipment as well.

To be able to schedule a project, all resources will have to be checked to establish if availability is a factor that needs to be considered.

Should a resource not be available in the time required in the schedule, adjustments will need to be made as to how the project is to proceed. Considerations will need to be made to use alternate resources to fulfil the requirements of the contract.

19 The planner will need to analyse the cost impact of substituting alternate materials or using substitute labour, either by subcontract or short term labour hire.

Resource allocation

In the initial planning stage for the work, it is necessary for the planner to assess the amount of resource required to complete parts of the work within specific allowed time frames. To be able to do this, the planner needs to resolve the amount of actual work required to be carried out for a section of work.

As an example, consider an estimate which has established that the construction of a section of formwork for a wall requires an amount of 160 hours of carpentry work to be carried out. Note that the estimate has established the amount of work, not the time it will take to complete. The time it will take to complete the work section is dependent on the resource made available to do the work. In our example, if 2 carpenter resource were allocated to the 160 hours of work and each resource worked an 8 hour day the time taken to complete the formwork for the wall would be

160 hours work 2 carpt / 8hrs per day = l0 days. Therefore, schedule task time is represented by the amount of work divided by the available resource to do the work and can be shown as a formula as follows: Schedule task time = Amount of work x Available resource

This is an important consideration when the planner is considering schedule time as the formula can also be written as follows:

Required Resource = Amount of Work x Schedule task time

In the example above, we can substitute the figures to work out the resource required for the wall formwork. The calculation would be as follows: 160 hours work 10 days =.l6hours/day (2carpt/8hrsperday)

20 In this regard, it is a requirement of the planner to decide the resource required for each section of work to achieve the time outcome required for the section of work being considered.

Planning Cumulative Resources Requirements

During the construction of some projects, the same type of resources maybe required over a range of tasks, or a task re- occurs at regular periods using the same resource.

As stated previously, resource can be Personnel, Materials, Plant & Equipment, Information etc.

When these types of activities occur, the planner needs to consider that as the resources are allocated to the various or re-occurring tasks, it is important to ensure that the same resource is not required for some other task. This is particularly the case where the same gang of personnel or the same equipment is required for a - number of tasks.

The planner needs to plot the use of the resource to ensure that a clash doesn’t occur. When using a computer based scheduling program, it is possible to allocate resources to tasks and the program will show where resources are over allocated. This allows the planner to recognise when a clash occurs and amend the resource use to remove the clash.

When using Gantt charts, resource allocation can be carried out manually by allocating resources to activities and then accumulating the information into a resource schedule. This will show if the same resource is allocated to more than one task at the same time and allow the planner to adjust the plan or the resource use to overcome the clash.

CRITICAL PATH NETWORK DEVELOPMENT

INTRODUCTION

The most effective method for analysing and programming project activities is undoubtedly network analysis, a well proven technique, used extensively in the professions and industry and known as Critical Path Method of scheduling building construction.

21 The principle of network analysis is a graphical display of the relationships between activities which consume resource and events which are points in time.

ACTIVITIES represented by arrows, join EVENTS, drawn as circles, which represent the starts and finishes of activities.

The logic of the system is that no activity may start at an event until all activities ending at the event have finished. Thus the network diagram provides for both sequential and parallel activities to be logically interwoven, to illustrate the total configuration of events. Against each activity arrow is noted a brief description (or identifier), the responsible participant, the estimated time duration, and the resource level required, where relevant. The network is analysed to establish the longest path, in tents of time, from start to finish.

This path is known as the Critical Path, and, by definition, delay to any activity on this path will delay the completion of the project Activities which are not on the critical path have spare time available which is known as FLOAT. In difficult situations, such as excessive demand for resources, non-critical activities can sometimes be rescheduled within the limits allowed by their float, to help smooth the use of resources.

CONVENTIONS OF NETWORK DIAGRAM DRAWING

When drawing network diagrams there are specific conventions that should be followed. You should refer to the Aust Standard AS 2443 - 1981 Glossary of Terms for Network Planning in the Building Industry. This standard sets out the tents and symbols that are used when network diagrams are drawn.

Generally, networks are drawn with the flow of the diagram going from Left to Right and where ever possible, the activity arrows should be straight, starting at a node on the left and ending at a node on the right.

When it is necessary for an activity arrow to pass over another activity arrow, the method of showing the cross over of the activity arrows should be followed as set out in these notes.

22 NETWORK DIAGRAM CONSTRUCTION

RULES AND CONVENTIONS OF NETWORK CONSTRUCTION

DEFINITIONS

The first step in the use of a critical path technique is the development of a network diagram. Definition of the basic terms used in such diagram are as follows:1

TERM SYMBOL DEFINITION

Network Nil A graphical representation of the activities and events in a project showing their inter-dependencies and inter-relationships

Activity An operation or process consuming time and possibly other resources.

Lead activity An activity that consumes time but not resource, for example, the curing time for concrete.

Dummy activity A logic link that consumes neither time nor any other resource

Event A defined stage in the progress of a project after the completion of all preceding activities but before the start of any succeeding activity.

23 By definition, activities represent the passage of time and/or the consumption of resources. They are points in time when all activities leading to them have been completed. Events are frequently referred to as MILESTONES or NODES.

ACTIVITIES BEGIN AND END AT EVENTS

These events are referred to as Preceding and Succeeding events respectively ( or as Tail and Head events). An event with no activities leading up to it is the Origin or Starting event; an event with no succeeding activities is the Terminal or Finishing event.

NETWORK CONSTRUCTION

A. The tail of an arrow indicates the earliest point at which the activity represented can commence and the head of the arrow represents the latest point by which the activity must be completed but the length of the arrow bears no relationship to the time of the activity. When the duration of the activity are written alongside

24 them they must be in the same time units (for example, days), but the network is not drawn to scale.

B. All event nodes must be numbered, but the head node must have a higher number than the tail node. There must be no duplication of numbers and sparse numbering is always used in order to avoid confusion.

C. Activity arrows show the time flow and job sequence. Where one activity depends on another, they are drawn in sequence

D. If two activities, each dependent upon the completion of a common activity, and can be carried out simultaneously, they are drawn with a common origin node.

25 E. It follows that all activities which start at a common node must depend on all activities which end at that node. Hence a basic axiom of network construction is as follows: An activity cannot start before any activities leading to its tail node have been completed.

F. No activity can lead to an event from which no activity departs unless this is the terminal event representing the objective of the project. Similarly, no activity can lead from an event to which no activity leads unless this is the starting point. There can be only one starting and one objective event; in other words, no activities are allowed to dangle - all must be tied into the network.

PARALLEL ACTIVITIES

A. Although it is possible in logic to have more than one activity leading between the same tail and head nodes, because of the limitations in some computer programs it is important that each activity have a unique pair of preceding and succeeding events.

26 B. In the case illustrated the activities of ordering materials and preparing the store are carried out between events 20 and 30 and occur in parallel. The way they are represented, however, is not acceptable because they are not uniquely deified for reference purposes. The network must be modified and this is done by including an extra event and a dummy activity before or after one of the parallel activities. A dummy activity does not consume time or resource.

10-20 Define materials requirements Satisfactory

20 - 30 Could represent either “Order Not Satisfactory materials” or “Prepare store

30 – 40 Deliver materials Satisfactory

Add a Dummy Activity and the network would be represented as follows:

LOOPING ACTIVITIES

No loops are allowed in the network. Each activity must bring you closer to your objective. The sequence illustrated is impossible in a logical network layout.

27 Wrong - Activities are looped WORKED EXAMPLES

The best way to explain the construction of a network diagram is to carry out a worked example. The first step is to list all the activities that make up the project and list them at random, that is without consideration of theft order or duration. These activities are then given identification ( I.D. numbers or similar) and the activities worked through to establish a list which identifies the activities on which the considered activity is dependent on as well as all the activities which are dependent on the activity being considered. By going through this process, a list similar to the list as set out for the Office Complex project on page 9 will be established. From this list, the network diagram can be produced.

As an example, set out following are a series of lists that show activities as identified (A, B, C etc) and the designated dependencies.

EXAMPLE 1: Assume you have a series of activities as listed and the dependencies between the activities are as follows:

ID DEPENDS TIME

A depends on Start 2 B depends on A 3 C depends on A 2 D depends on B,C 1 End depends on D

The diagram would be shown as follows:

28 Draw a network diagram for the following

ID DEPENDS TIME

A depends on Start 2 B depends on Start 2 C depends on A,B 3 D depends on A 2 E depends on C 3 F depends on C,D 2 G depends on E,F 2 End depends on G -