INN OVATIVE SOLUTIONS Demystifying prefabrication New Zealand is home to a new generation of prefabs. What does PrefabNZ CEO Pamela Bell see as the case for prefabrication on New Zealand construction projects? By Peter Cunningham, Chief Executive, Construction Clients’ Group

refabrication, or prefab for short, refers to any part of a building that is made at a different location than the final building Psite, which is why it is also referred to as off-site construction.

What is prefab? Off-site construction occurs in a manufacturing plant specifically designed for this type of process. Individual components, panels, modules or the complete building are construct­ ed in the factory and then transported to the site. Once on site, the building will be installed onto a permanent foundation by fastening it to the ground and to other modules and covering and sealing the seams. These buildings meet the applicable building codes and are indistinguishable from traditional site-built Albany Senior High School in Auckland made extensive use of prefab technologies during its construction in 2009. construction techniques. Prefab can also be used as a complementary system to traditional construction. It comes in infrastructure projects (such as hydroelectric But what are the societal and sustainability all shapes and sizes, from small components scheme housing) to some of the first one- impacts of prefab construction methods? such as prenailed wall frames, to panels (2D), piece fibreglass bathrooms (from Industrialised Reduced local impacts larger modules (3D volumes) or even complete Building Systems in the 1970s). Interest in A key feature of prefab is that much of the buildings. Hybrid prefab is a mixture of several prefabrication has been renewed through the process is in controlled factory conditions. This prefab systems or prefab with traditional sustainability agenda and ‘off-site movement’ reduces the amount of time spent on site, which construction. Prefab can be any combination of around the world. New Zealand is home to a leads to reduced local impacts. timber, concrete, metal or plastic. new generation of prefabs such as bachkit, port- Experience shows that prefab hotel rooms It can be used for a variety of purposes a-bach, HABODE, iPAD, K Bach and others. can be assembled on site and completed ready including residential, educational, healthcare A lot is happening in the prefab world, but it to use in less than half the time of a traditionally and commercial applications. Buildings can often happens in isolation and there is a need built hotel of a similar size. This means that the range from a few modular units to several to coordinate, inform and in many cases, re- site is disrupted for a shorter period, reducing hundred. They can be arranged in architecturally educate. The time is right to collaborate and noise, pollution and local traffic disruption. The pleasing configurations and can be many market the benefits to the world. lightweight nature of the construction also offers storeys high. potential for smaller foundations and therefore Many benefits less groundworks, again reducing disruption Prefab has a role in productivity Until recently, off-site fabrication, particularly in when bringing in concrete and removing spoil. Prefab has a key role to play in improving industry housing, has, rightly or wrongly, been associated However, large deliveries of volumetric or panel efficiency, effectiveness and productivity in the with poor quality, a reduction in flexibility and units can be disruptive to the area and need design and construction process. choice, and higher costs. Market resistance careful logistics management to avoid problems. PrefabNZ is building on an innovative and prevented significant uptake of the technology, Financially, the shorter construction period rich history of prefabrication in New Zealand despite examples here and abroad that illustrate provides a quicker return on investment for the – from large-scale government investment in its technical feasibility and benefits. client and reduces overheads.

26 BUILD 124 June/July 2011 Not to be confused with its mobile namesake, the iPAD is a Kiwi innovation in lightweight kitset Prefabricated modules can take almost any size and shape, and use combinations of building. construction materials.

Better quality and reduced defects Enhanced health and safety locally. They provide a long-term economic and In other industries, such as car manufacture On-site construction work can be dangerous. often social service to the community. and electronics, we expect zero faults when we Off-site manufacturing allows much of the Greater efficiency purchase goods, yet defects in buildings are process to be carried out in more controlled Building sites are notoriously inefficient in common at handover and are often costly and and comfortable factory conditions where their use of labour and materials. Studies in time consuming to rectify. safety requirements can be more easily met the United Kingdom found that site labour can A construction site exposed to the elements and policed. be up to 50% less efficient than factory-based doesn’t provide ideal conditions for high-quality The use of scaffolding on site is a particular activities. workmanship and doesn't provide attractive concern, and some off-site manufacturing Volumetric construction using prefabricated working conditions in winter. schemes try to eliminate the need for scaffolding modules also allows buildings to be dismantled Factory-based activities allow better and by integrating claddings during manufacture in and the modules reused at a different location. safer working conditions and are more likely to the factory. Improved logistics lead to higher quality. It is easier in a factory Conversely, the use of heavy lifting equipment Prefabrication generally leads to fewer site to set up quality control procedures, with to locate the prefabricated components on site deliveries when compared to traditional testing, prototyping and checking, for example, requires careful management. construction methods. electrical and water installations in volumetric Improved environmental performance Recent monitoring at a modular site suggests units can be tested prior to leaving the factory. A building’s thermal and acoustic performance that deliveries were reduced by up to 90% when Feedback suggests that far fewer call backs are depends on the quality of workmanship and compared to a nearby site constructing a similar necessary to correct defects after completion of supervision. For instance, it’s important building using traditional techniques. However, buildings using prefabrication. This is a significant to correctly install insulation and ensure these are generally large vehicle deliveries cost and efficiency benefit to the builder and leads airtightness to ensure the building’s often travelling considerable distances from the to satisfied customers. It also improves efficiency in environmental performance once it is in use. factory. the use of resources and reduces waste. Reports from North America show higher Prefab construction also requires less on-site Less waste in manufacture thermal performance in homes that use off-site labour for a shorter period of time, so a well Construction waste is one of the principal waste manufacturing techniques. managed site using prefab should significantly streams to landfill sites. Factory manufacturing Factory manufacturing also allows workers reduce the amount of traffic it generates. allows better management of the waste stream, to be better trained and supervised and allows more efficient use of materials, more accurate regular checking and testing of performance. Opportunity for improvements ordering and better storage conditions. Social benefits Prefabrication offers an opportunity to improve Any waste in a factory is easier to collect and A job manufacturing prefab components is both efficiency and sustainability. However, reuse or recycle. Many prefab manufacturers generally more stable and long-term than site- many of the benefits are not yet fully realised, have recycling facilities installed so that waste is based employment, so employers are often and the industry has much to learn to fulfil the sent back to their source for recycling, reducing willing to invest in workforce training. Off-site potential of this technology. the costs of waste disposal. There is further fabrication requires a highly skilled and flexible Much work is needed as prefab is often still potential for reducing waste if the designer workforce to be efficient, which necessitates perceived as a project innovation rather than is prepared to use standard sizes, which can greater training by employers. industry best practice. reduce the number and size of off-cuts. Building sites are temporary employment For more information, see www.prefabnz.com. Assembly of prefabricated components on locations, so they generally offer little long-term Research by Pamela Bell for her Master of site generates little waste, as the components amenities for the local community. Factories, on Architecture thesis, Kiwi prefab: prefabricated arrive on site pre-engineered and ready to the other hand, are often closely linked to the housing in New Zealand, has been used in this assemble together. community, with much of the workforce living article.

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