P. Rajagopalan and M.M Andamon (eds.), Engaging Architectural Science: Meeting the Challenges of Higher Density: 52nd 145 International Conference of the Architectural Science Association 2018, pp.145–152. ©2018, The Architectural Science Association and RMIT University, Australia. Learning from the past to build tomorrow: an overview of previous prefabrication schemes
Milad Moradibistouni Victoria University of Wellington, Wellington, New Zealand [email protected] Nigel Isaacs Victoria University of Wellington, Wellington, New Zealand [email protected] Brenda Vale Victoria University of Wellington, Wellington, New Zealand [email protected]
Abstract: The world population growth can potentially lead to a shortage of appropriate houses in many countries. It can also increase the cost of land, which will directly affect the price of houses. Given the advantages of prefabrication, this method has the potential to provide numbers of high-quality houses in a short time. However, despite many historic attempts to produce prefabricated houses, there have been many failures. This paper presents a review of previous house prefabrication schemes to better understand the factors involved in their failure. Prefabrication schemes in five different time periods have been reviewed. The review looks at the construction-related needs in each period, the way the method of prefabrication responded to those needs, and any weaknesses of the method. The review ends by suggesting the most important factor for the potential of prefabrication is the current negative perceptions of stakeholders, including house owners and financiers. These negative perceptions come from early prefabrication schemes which focused on quantity and speed over quality and aesthetic aspects, and the fact these schemes were often linked to shortages of conventional building materials.
Keywords: Prefabrication; housing; housing shortages; material shortages
1. INTRODUCTION
A building can be constructed using different methods and materials. Choosing the best amongst the various options is affected by factors such as availability, cost, and location of site. As an example, in most vernacular architecture indigenous materials are used as these are cheap, readily available, and have the most conformity with climate (AIA, 1976). Despite the effect of materials and climate on the choice of construction method, it is also affected by needs and aims of the building. For example, the choice might be different if the aim is to create an energy-efficient or zero energy building, or where time is the main constraint and the building has to be ready as quickly as possible.
This paper has studied the construction-related needs of societies in five different time periods and the way prefabrication responded to those needs. It has also looked at any successes of the industry and investigated the reasons behind any failures to see what factors need to be considered to ensure the success any future prefabrication venture. This paper is mainly shaped around the history of prefabrication in UK, United States of America and New Zealand while also noting important examples from other countries.The first step in this analysis is to define prefabrication and its different types.
2. PREFABRICATION
Prefabrication is often regarded as synonymous with standardisation. Le Corbusier compared the process of building a house with a car production line and believed that the construction industry could be streamlined if the process of building a house became more like that of making a car, thus moving production from the site to the factory (Vale, 1995, p. 64). Prefabrication has come to mean a method of construction whereby building elements, ranging in size from a single component to a complete building are manufactured at a distance from the final building location. These elements are then sold and carried to the final location, usually by motor vehicles, where they are assembled and attached topre-made foundation (Seratts, 2012, p. i).
These can be classified based on the materials and systems used or the degree of prefabrication Moradibistouni( and Gjerde, 2017). Based on the degree of prefabrication five groups emerge Figure( 1). 146 M. Bistouni, N. Isaacs and B. Vale
• Component: this group comprises simple pre-cut and pre-shaped elements, and the more complicated sub- assemblies, made by combining more than one element (Bell, 2009). This group has the least degree of prefabrication but has more flexibility in terms of the final house. It usually needs more onsite work with more potential for defects (Boafo, 2016).
• Panel: panels are two-dimensional elements made up of a limited number of components, joined together in the factory. Panels are easy to transport using a flat back trailer and offer a high level of flexibility with less on-site work compared with components. Panels can be simple pieces which need more on-site work or made in more complete forms that include cladding, doors, windows and even wiring and plumbing (Bell, 2009; Elitzer, 2015).
• Module: modules are three-dimensional units made up of panels joined together in the factory. Modules, which are approximately 80-95% completed before leaving the factory, are very useful for buildings with a repetitive geometry (Boafo, 2016).
• Hybrid prefabrication: a combination of the modular system, usually for service zones, and the panelised system, for the building envelope. This combination makes transportation easier while decreasing the possibility of defects as the complex service zone is factory made (BRANZ, 2013).
• Complete Building: the entire building is factory constructed and moved by a heavy haulage vehicle to the site, where it is attached to the permanent foundations (Steinhardt, 2013).
Figure 1: Different types of prefabrication. (Source: Moradibistouni and Gjerde, 2017)
3. METHODOLOGY
This paper is part of a larger study investigating the potential use of prefabricated Accessory Dwelling Unit (ADU) as a potential solution to the shortage of housing in New Zealand. An ADU is a secondary residential unit providing the basic needs of dwellers, with no dependency to the primary unit (Smith, 2017). This paper is a literature-based investigation that explores the potential for prefabrication to act as a resource-efficient method of construction by looking at what has succeeded and failed in the past. This paper explores the history of prefabrication in five different historical periods: before WW I; during both World Wars; between the two World Wars; after WWII; and the present time. The scope is limited by only considering prefabrication related to housing. The similarities of this effect in both World Wars means that here they are treated together.
The paper discusses how prefabrication helped the construction industry in the selected countries to meet market needs by exploring the potential benefits and weaknesses of the prefabrication method used during those periods. In doing this it focuses on the reasons behind failures to see what can be learned from them. In each period the reason prefabrication was chosen as method of construction is outlined and the ability of this method to respond to those needs is investigated.
4. PREFABRICATION BEFORE WW I (BEFORE 1914)
The history of prefabrication dates back to the beginning of nomadic life and times when people had to migrate due to external threats or environmental conditions. The main reason people looked to prefabrication was their need to have houses which were easy to assemble, disassemble, and transport (Herbers, 2004, p. 14). These early prefabricated shelters were made of some pre-cut structural elements, usually timber, joined together using precut holes and/or ropes and covered by an envelope of leather, woollen fabric or other natural materials. Examples of these shelters can be found in the civilization of the early Persians, North American Indians and Mongolians, respectively called Black Tent, Tipi and Yurts. Other examples can be found in different ancient nations (Giller, 2012). Learning from the past to build tomorrow: an overview of previous prefabrication schemes 147
In the same way emigration to British colonies in the 18th and 19th centuries, led to the development of transportable prefabricated houses and housing components. The reason behind these prefabricated buildings was again the need for houses which could be easily transported and assembled, often on an unknown site. Most of these houses were made of timber and were covered by canvas and later clad with weatherboarding (Smith, 2009). These houses could even be assembled by unskilled owners. Once the immediate need for housing was satisfied and sufficient building skills accrued in the new colonies, the need to ship prefabricated houses was less urgent. One result of this is that little can be learned about failures as firms just disappeared.
5. PREFABRICATION DURING THE WORLD WARS (1914-1918 AND 1939-1945)
During both World Wars, most factories changed their function to serve the war effort. In the UK, and other countries, the draft reduced the availability of men to operate factories or build, leading to a significant shortage of houses, while the focus on the manufacture of war goods led to a shortage of building materials (English Heritage, 2011). Particularly in WWII, there was a need for methods of construction with less on-site work which used materials more efficiently (Harrison, 1945). This gave a spur to prefabrication as this method was potentially able to reduce use of raw material by 40-50% and construction time by 35-57% (Phillipson, 2001, p. 3; Gorgolewski, 2005, pp. 125-126; Britto, 2008, p. 14).
One of the most prominent prefabricated structures built during WWI was the Nissen hut, designed by Canadian engineer Peter Nissen, as a cheap, portable shelter for the British Army. The building, which was made of corrugated sheet metal pulled into a half cylinder and fixed on brick foundations, could be used for different functions such as a shelter, hospital, or armoury (Florian, 2013; Decker, 2005, pp. 5-7). The Nissen hut has been claimed as the first mass-produced prefabricated building (Mallory, 1973. 81). It was easy and fast to transport and be assembled by unskilled workers but had weaknesses. The biggest was the lack of thermal insulation which made the hut cold in winter and hot in summer (George, 1937, p.63). During WW II, the idea behind the Nissen hut was optimized and better insulation was added. In the USA this became the Quonset hut (Decker, 2005, p. 7). The shortage of houses during both World Wars, coupled with the shortage of materials during and afterwards, helped to bring the benefits prefabrication to fore. The effect of this on housing is described in the next section,
It is estimated that by the last year of WWII, after six years of war, 475,000 houses in the UK were destroyed or uninhabitable (Barr, 1958). In 1944 Prime Minister Winston Churchill released his plan for constructing approximately 300,000 permanent and 500,000 temporary houses without increasing demand on conventional building resources and skilled labour (English Heritage, 2011; Finnimore, 1989). By switching production to the factory, prefabrication could potentially increase the efficiency of use of materials and labour by 50% while using 40% fewer man-hours (Chiu, 2012, p. 16).
The result was the development of non-traditional houses, many of which drew on the systems used for war time huts and other buildings. This led to problems related to sound and thermal insulation, and the fire resistance of houses (Hayes, 1999, p. 54; Stevens, 1995; Nash, 1954). There were also serious concerns over the quality of prefabricated houses as there was an attitude of valuing quantity over quality in their design and construction (Hashemi, 2013). More importantly, the 1944 temporary houses in the UK were designed to last approximately 10-15 years, but most were used for much more than this period of time, which led to defects and leaks (BRE, 2004). In fact although “some 156,623 temporary bungalows were produced for rent under the aegis of the 1944 temporary housing program [in the UK]” (Vale, 1995, p. 1), the program was wound up because it was considered to be too expensive. The prefabricated temporary houses had cost more than expected.
6. PREFABRICATION BETWEEN THE TWO WORLD WARS (1918-1939)
After WWI the shortage of both houses and materials gave a spur to prefabrication. In 1927 for the first time in Scotland more than 20,000 non-traditional houses with some type of prefabricated system were completed (Stationary Office, 2001). Some, like the Atholl and Weir systems, had walls of steel plate, using the skills developed building ships for the war effort (Ministry of Works, 1944, pp. 80-84). The poor quality of joints, ventilation and lack of sufficient thermal mass and resistance meant these houses needed a lot of heating. However, there were other ventures in prefabrication in this period. The first is the many systems that used concrete, beginning with Atterbury’s 1918 standardized prefabricated hollow concrete slab houses at Forest Hills Gardens (Pennover and Walker, 2009, pp. 255-265). Concrete was so used so often by house prefabricators in the USA that in the 1934 review of 98 illustrated systems of prefabrication by Bemis and Burchard, and based on the major material in hybrid systems, found 50% were concrete, 38% steel, 10% wood and 1% plastic (Vale and Skinner, 2018). These developments in concrete prefabrication were to lead to the many panel based systems developed for apartment housing because of the speed these offered, though many also suffered from poor indoor environments and lack of comfort.
Another boost to prefabrication between the wars came from the need to provide temporary accommodation for workers on big infrastructure projects, such as in the USA the dams built under the aegis of the Tennessee Valley Authority. These demountable houses were of wood and came in sections that could be transported on the public highways (Huxley, 1943, p. 112). This in turn gave rise to associating prefabrication with temporary and trailer based housing. 148 M. Bistouni, N. Isaacs and B. Vale
7. PREFABRICATION AFTER WW II (AFTER 1945)
After World War II, the need for a new method of construction which was faster and more efficient continued in the face of a shortage of conventional building materials and labour (Turner, 2015; Waskett, 2001). In addition to needing more houses in less time and using non-conventional materials and unskilled workers other reasons, especially in the UK, include worry about the shortage of work and the need to find jobs for the demobilized troops; and the emergence of support by the Ministry of Works for prefabrication (Gay, 1987).
From 1945 to 1947, the UK government gave a heavy subsidy on non-traditional construction methods so as to encourage their use (Hayes, 1999). However, once the subsidies were cut in 1947, prefabricated buildings failed to compete economically with traditional methods, in part because they needed the application of new technologies in different stages of manufacturing, transporting and assembling.
Prefabrication is most efficient when used for larger numbers of buildings, but it has higher start-up costs than conventional house construction. The costs of creating suitable designs, factories in which they can be made by a specially trained workforce under appropriate management systems, and systems to transport and place on-site all have to be paid for before even one house has been completed. This capital investment continues to be a problem for prefabrication-based construction companies, which in turn can lead to financial institutions treating prefabrication companies as having greater risk than conventional construction businesses.
Stakeholders were still struggling with the post-war financial crisis and shortages of materials and workforce (Finnimore, 1989; Hayes, 1999). Moreover, in the 1950s off-site construction was hampered by site delays, the inability to stay within expected costs, and the inability to estimate realistic on-site man-hours (Hayes, 1999). As Mckean (1995) and Pirrozfar (2013) have noted, there was also a conflict between manufacture-based production of houses and the aesthetic side of architecture. Hashemi (2013) also pointed to a lack of policy in post-WW II for monitoring buildings constructed using new technologies. These weaknesses combined to cause, such as the 1968 collapse of Ronan Point, a 21-storey prefabricated, panelised London tower block, which affected the success and acceptance of prefabrication (Pearson, 2005).
8. CONTEMPORARY PREFABRICATION
Current shortages of affordable housing in countries like New Zealand are again raising a case for using prefabrication construction methods. However, there are other reasons for looking again at prefabrication. At present, humanity is using energy and environmental resources at a rate that is equivalent to using the resources of 1.6 planets, and without change, it will be 2.0 planets by 2050 (Global Footprint Network, 2016). Additionally, Conti (2016) has predicted that world energy consumption will increase by 48% by 2040. Moreover, in 2015, the average concentration of CO2 in the atmosphere (399 ppm) was an increase of 40% in comparison with that of the mid-1800s and the highest level reached in the last 800,000 years (Hong Kong Observatory, 2016). Construction methods are important as “…the buildings sector and people’s activities in buildings are responsible for approximately 31% of global final energy demand and approximately one-third of energy- related CO2 emissions.” (Global Energy Assessment, 2012) The construction industry plays an important role in the use of energy and its environmental impacts, making it necessary to use methods of construction which use resources more efficiently and in a more environmental friendly manner. Theoretically, prefabrication could be a good replacement for traditional methods as it uses resources of energy and water 50-55% and 30-50% more efficiently respectively, and can also reduce CO2 emissions by 35% (Britto, 2008, p.14; Phillipson, 2001, p.3). However, the current negative perceptions of stakeholders toward prefabrication, which seem to have originated from the past experiences, some of which have been mentioned above, is probably the biggest obstacle to the wider use of prefabrication
“People have got the idea that it [prefabrication] means jerry-building, tumbledown shacks, caravans, shoddy work, ribbon development, draughts and leaks and everything that’s bad in the building. The Government itself seems to hold the confused opinion that prefabrication means something temporary” (Vale, 1995, p.17).
9. PREFABRICATION AND THE FUTURE
World population is growing fast. The population which was approximately 2.5 billion in 1950 reached more than 7.5 billion in 2018 and is predicted to rich to more than 10 billion by 2050 (United Nations, 2004). Close to 65% of global population is predicted to live in cities by 2040 compared to 55% in 2012, and this is also forecast to equal a 25% increase in energy demand (ExxonMobil, 2016, p. 12). These data show there will be a growth in number of houses needed. For example, New Zealand is today facing a shortage of 71,000 houses. As a result of population growth, this shortage of houses increased by 40 houses a day in 2017 (Miller, 2017). The world community needs methods of construction able to provide more houses in less time – a role for prefabrication.
In addition to the shortage of houses, population growth has more direct effects on the construction industry. Dunkerey Learning from the past to build tomorrow: an overview of previous prefabrication schemes 149 argues the increase in demand for urban land has a direct relationship with population growth, leading to increases in cost of land. The easiest way of overcoming this, would be converting other types of land, such as rural, to urban land to accommodate more people. However, this conversion relies on an expansion of the road network and the provision of new infrastructure supplying services such as electricity, sewage, and drinking water, as well as other services such as policing, which can put an extra economic pressure on governments (Dunkerey 1983, p. 6). Although Dunkerey’s (1983, p. 6) view was “land location is specific, and existing urban plots cannot be reproduced” there are other ways of reusing or expanding the use of existing urban land.
One is the use of Accessory Dwelling Units (ADU). ADUs are smaller, secondary residences, placed on the existing plot of a primary residence. They usually appear where there is existing infrastructure (Ross, 2016, p. 17). ADUs can be classified into four types according to Smith (2017).
• Partitioned ADUs: these units are the result of dividing an existing dwelling into two or more units by using partitions inside the existing house envelope.
• Converted ADUs: converted ADUs are the result of converting an existing independent space, such as a garage or basement to a living unit.
• Attached ADUs: this group of ADUs is the result of constructing or attaching a unit to an existing house.
• Standalone ADUs: these ADUs are constructed completely from foundation to finishes, and as a separate building from the primary dwelling but on the same lot.
A recent study shows that partitioning existing house into smaller units could add over 180,000 new houses to the NZ housing market with no impact on unused residential land (Smith, 2017).
Matching the benefits from the different types of prefabrication parallel to the different types of ADUs shows the high potential for prefabricated ADUs. Panelised prefabricated systems could be used to build partitioned and converted ADUs, while modular prefabricated systems can be used for building attached and standalone ADUs.
However, aside from potential benefits, there are some considerations regards to build and use of ADUs. One of these is restrictions related to building an ADU on a lot which already includes a house. This means the ADU must be ready quickly in order to minimise the effects on the residents, or they must be moved out of the primary house during the construction. This can put financial pressure on the project. Moreover if, for example, the ADU is going to be located on the backyard, the way the ADU is to be placed (e.g. lifted by crane), must be considered at the first design stages. Different councils and legislation may set different requirements, such as the maximum allowed site coverage. This variety of rules makes design of ADUs more complicated. The possibility and efficiency of using ADUs are under investigation in the larger study commenced in 2016.
10. EVALUATION AND CONCLUSION
The aim of this paper was learning from the past by reviewing part of the history of the prefabrication industry so as to see what prefabrication in the future might offer. The intention was to see what the needs of societies were in different periods of time and to look at possible benefits of prefabrication in relation to those needsTable 1 collects together the main results of this review. 150 M. Bistouni, N. Isaacs and B. Vale
Table 1: Review summary
Time period Most important needs Responses of prefabrication to needs Reasons for failures Ease of transport and Use of timber as being light and easy Pre-WW I (1914) - assembly to assemble Systems created which provided less Speed in supplying No proper sound and thermal than ideal interior environments such During WWI & II buildings with less on-site insulation and fire resistance; as the Nissen Hut. (1914-18 & work, efficient use of valuing quantity over quality; using 1939-45) materials and less need prefabricated houses for more than Prefabrication produced temporary for skilled labour their expected lifetime house quickly Houses in quantity and Lack of comfort Proliferation of many different Between WWI & II produced at speed competing systems using different (1918-1939) Not putting efforts into a few materials Demountable houses systems and perfecting these Experimental systems such as steel Site delays, cost overruns, Shortage of houses and frame and concrete panel were aesthetic concerns, and cutting Post-WW II (1945) of conventional building developed, including for high rise financial support (subsidies for materials and labour blocks prefabrication). Housing shortage Research shows prefabrication could Negative perceptions of be 50-55 % more efficient in use Need to make efficient stakeholders toward prefabrication Present time of energy, 30-50% more efficient use of resources and be originating from historical use of water and could reduce CO more environmentally 2 experiences emissions by 35% friendly More efficient use of developed lands to Prefabrication could be used to create Future - provide houses for different types of ADUs growing population
Table 1 shows that pre-WWI, the most important concerns regarding prefabrication were much like those of the early nomads – the ability to move houses, often over considerable distances using animal (for example yak) or wind (ship) power. Such buildings needed to be easy and quick to assemble. During and immediately after both World Wars due to the urgent need for more houses, the priority of governments was supplying houses in quantity rather than focusing on quality, the former in some cases leading to building temporary houses. Because of that hurry, most of the prefabricated houses that resulted did not have the quality people expected or the quality the industry potentially could have delivered. As the urgent need for more houses disappeared, just when quality could have become the focus, governments cut support for prefabrication, and without the subsidies the industry was uneconomic. At the same time, a general perception was formed linking prefabrication with the low quality and temporary houses of the war years and the years between them. The result was disinterest in prefabrication, which meant less chance of benefitting from its advantages.
In the present time, there is a need for a method of construction that can use energy and materials more efficiently. Moreover, due to rapid population growth, the world will soon be faced with a major shortage of houses, as has already happened in some countries. Due to its modern benefits prefabrication could provide the next generation of houses in the form of prefabricated ADUs by using already developed land. However, learning from the past, the quality, design, and aesthetic aspects of prefabricated buildings should be considered as important as the quantity and mass production aspects of prefabrication. Clear and explicit rules need to be defined for prefabricated buildings, with monitoring of their production, transportation and assembly. Another important factor to be considered is the importance of the support, mostly financial, of the fledgling prefabrication industry by governments. The main reason for this need of financial support is the fact that while payments in traditional buildings can be done in different stages, in small amounts, in prefabricated building most of the payment should be done at the beginning of the process, one-stop shopping. Moreover, financial institutions prefer to invest their money on traditional made houses as they believe that prefabricated houses are not good investments. Finally and most importantly there is an urgent need to show what this industry can already do in terms of producing quality houses to change any negative perceptions toward prefabrication based on its history.
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