Using prefabrication materials, or “prefab”, dramatically speeds up construction time, lowers material costs and increases quality assurance.
Prefab refers to any part of a building that has been assembled offsite in a factory or manufacturing facility and transported in complete or sub-assemblies to the construction site. It is a broad term and refers to a number of different systems or processes, including structural, architectural and services elements.
Prefabaus - the peak body for Australia's off-site construction industry - breaks up prefab into two main families, 2D prefab and 3D prefab. They can be used in conjunction with each other, on their own or with traditional construction methods.
2D prefab is made up of pre-cut, pre-sized, pre-moulded or pre-shaped components that are assembled or installed on site. They often arrive as flat-packed panels or non-volumetric systems, ready for assembly. They might form the building envelope, stair cores, internal load bearing walls or lighter partitions. They might be open or closed panel systems, precast concrete panels or other panel types. 2D prefab is easier to transport, lends itself to mass customisation and has infinite construction options, combined with speed of assembly.
3D prefab systems are three-dimensional structural units which are combined at site with other units or systems, or might comprise an entire small building. They include pods, which are generally not structural modules, such as bathroom or kitchen pods. They are a fast way to build, as they can be manufactured concurrent with site preparation, and can arrive on site almost complete. 3D prefab systems can be joined together to create larger spaces and they are increasingly demonstrating their ability to go multi-level. The elements of 3D prefab may be structural elements, architectural elements or services elements, or they may be a hybrid of these.
Due to their production methods, prefab homes can be delivered on tight budgets and with a positive environmental response. Image: Arkit
Using prefab materials allows for the off-site process to take place simultaneously with site preparation activities, resulting in a significantly reduced overall construction period of a project. This reduced construction time can lead to less labour costs and delays due to bad weather are minimised. There is also a faster time to occupation, which means clients can begin generating an income sooner.
Greater control over the finished product can be achieved, as on-site wet trades can be minimised or eliminated and quality can be created in a factory controlled process. The indoor environment allows for buildings and components to be protected from climate extremes, vandalism and theft. Safety is also easier to control in a factory and most of the work can be conducted at waist height, and workers know the machinery and systems of the factory. Furthermore, the environmental impact of the construction process can be minimised.
Waste in construction is a big issue. Approximately 19 million tonnes of building and demolition waste was generated in Australia in 2008-09. Of this, 8.5 million tonnes (45 per cent) went to landfill while 10.5 million tonnes (55 per cent) was recycled. A number of states, including Victoria, South Australia and Western Australia, have ‘towards zero’ waste strategies and the Australian Government’s “Your Home” website recommends choosing prefab to reduce waste, as each element is designed to be an exact fit.
Prefab buildings are more sustainable than those constructed on-site through manual labour and are potentially twice as efficient compared to on-site building.
There is minimum site disturbance and due to the quality control systems of a factory, the buildings can be better sealed, have improved insulation placement and better energy efficiency.
A CHANGING REPUTATION
Despite their benefits, prefab has had a pretty bad rap in the past.
“Historically in Australia, prefabricated homes have been viewed as more temporary and low budget housing. That’s no longer the case,” says Bill McCorkell Managing Director of Archiblox.
“These days, architect-designed prefabricated houses are getting recognition Australia-wide as high-end architecture with sophisticated building technologies. Luxurious prefab homes are starting to catch on as a new trend that brings together cutting-edge technologies and high-end materials to create a visually distinctive building.”
McCorkell says it’s no longer just “early adopters” who are reaching out for a modular build.
“People are now more informed and can see the benefits of this sophisticated design and build method,” he says
“They are also very interested in the installation process - seeing a house appear as if out of nowhere is always exciting.”
The two bedroom Avalon House by Archiblox has a 16m by 4.6m module size manufactured in Victoria and shipped up to NSW. It is situated on one of the most sought-after sites on Sydney's Northern Beaches.
While prefab used to conjure up images of demountable school buildings, there is now a much wider range of products on offer, more players in the market and increasingly more sophisticated design.
Chris Barnett, Managing Director of Habitech Systems, a provider of flat-packed, high-quality manufactured building components, says the perception of prefab systems are slowly changing.
“Time savings and the ability to control quality better are driving the adoption of pre-fabricated systems in the industry, especially pre-fabricated bathrooms into high rise projects.”
Alpine House by Habitech Systems was created by Habitech using their innovative SIP building system.
The time-saving qualities of prefab are now driving its use in different sectors of the industry, with Habitech seeing a growing interest in hospital construction, particularly due to the reduced building disturbance on operating health care sites.
“However, we still field a lot of enquiries looking for pre-fab options as a cost saving, rather than as a better quality proposition, but the information revolution and shows like Grand Designs are educating Australians as to how poor the quality of our housing is,” Barnett says.
Prefab is changing that way architects work, by providing them with a range of better designed and readymade building elements to work with.
“Different systems create different levels of design limitations, from prefabricated building elements working to set dimensions, through to 'truck the box' prefab approaches being set on fixed transport module sizes,” Barnett says.
Over the next 20 years, Barnett predicts prefab will change the way we build.
“The housing market is now globalised and overseas offers will simply provide better quality buildings, at lower prices with guaranteed quality…Habitech's modular building fabrics are already allowing us to build houses with roof-top PV's that produce more electricity than they use - zero emission and no energy bills.
“Australia needs to innovate, or lose a fair percentage of our construction industry to overseas companies,” he adds.
Similarly, Jan Gyrn, Managing Director of Modscape agrees the perception of prefab has changed.
“Australia is constantly learning from the methods and systems used overseas in Europe, Asia and the USA and continues to squash outdated views associated with traditional prefab construction.”
“Today there are many examples that showcase the quality and design flexibility of prefabricated construction,” she adds.
Industry appreciation and understanding of the design possibilities of prefabrication are growing thanks to outfits like Modscape. Image: Mt Martha House by Modscape.
Modscape uses modular design and prefabrication to create architecturally designed, sustainable homes and buildings. They work collaboratively with architects to develop their design and minimise risk in the building process, as they design, cost and build in-house.
“The use of prefabricated materials in the construction industry is improving efficiency across the entire building process,” Gyrn explains.
“Architects are also seeing the benefits and designing to suit a prefabricated, modular build. The delivery method of our modular construction is informing the design process, but design flexibility is retained.”
Designed by Jackson Clements Burrows Architects, Modscape recently constructed new prefabricated modular learning spaces and associated amenities for Monash College in Clayton. The impressive time-lapse video documents the build from construction to installation and completion
Although they have come a long way, Gyrn predicts the use of prefabricated materials and systems will continue to evolve.
“All parties want the certainty that a project can be delivered on time and on budget. Greater appreciation of the industry and greater understanding of the design possibilities coupled with accelerated construction time, less waste and less site disruption is making prefabrication more and more exciting,” he says.
However, prefab is not without its limitations.
THE OTHER SIDE OF THE COIN
When using prefab, there can be a higher initial construction cost and there is a greater need for coordination of build sequences, to ensure delivery and installation run smoothly and the speed of using prefab is optimised.
The cost and constraints of the shipment method must be taken into account, especially if the factory is located far away from the site. For example, modular structures transported on a flat-backed trailer will be limited in length, width and weight based on the capacity of the truck. Transport may also be affected by daytime traffic restrictions in city centres, maximum load capacities and height restrictions under bridges.
Due to a lack of knowledge of the manufacturing processes among architects, a lengthened design development stage is common with architects not familiar with the process of modular construction. Barnett noted there are some design limitations, however this will vary depending on the manufacturer and their means and methods of production.
PREFAB IN ACTION
Arkit is an architect-led design and build group who specialise in high quality, customised prefabricated building solutions. The group focus on challenging the perceived design limitations associated prefabricated construction and offer both panelised and modular construction options.
Two projects recently completed using Arkit’s modular system include the Phoenix Early Learning Centre project and the Light House project. The Phoenix Early Learning Centre project is the first prefabricated building commissioned by the Victorian Department of Education and Training through a design and construct delivery method. Comprising a 66-child early learning facility, the centre was built within an operating school site. Using prefabrication enabled site based construction time to be limited to eight weeks. The Light House project is a new-build residential project located in a sensitive coastal environment. Built in two modules, the project was factory built and delivered to site fully fitted out. Designed to maximise outdoor interactions, the project was constructed in 12 weeks.
Arkit is currently working with several clients affected by the Great Ocean Road bushfires. Their panelised system will enable architect-designed BAL rated homes to be delivered in around a third of the time of traditional site based construction. Arkitit has approached the Office of the Victorian Government Architect to request the inclusion of a prefabrication option within the suite of standard designs to be developed for the rebuild.
A recent new-build Arkit project, Tucker House, was constructed from a series of wall, roof and floor cassettes. A key consideration in the selection of this system was the difficult nature of the site. The project was located on a steep site subject to land slip, but through the use of panelised construction, the project was completed in 12 weeks.
House of Häagen-Dazs by Archiblox
Archiblox’s House of Häagen-Dazs at Federation Square Melbourne. Photography by Tom Ross
The House of Häagen-Dazs was used to introduce the American ice cream brand Häagen-Dazs back to the Australian market place after a hiatus of nearly 30 years. Archiblox designed a prefabricated Pod with a construction time of 10 weeks. The project used advanced prefabricated building methods and materials that carry high sustainable properties.
Bill McCorkell Managing Director of Archiblox says The Taboo Group got in touch as they wanted to use Archiblox’s prefabricated method for a quick turn around “and also because they loved our designs, and sustainable qualities”.
The Pod is constructed of carbon neutral timber cladding on the exterior, plywood interiors including seating and the ceiling, and recycled blackbutt timber planter boxes. Currently the Pod operates on grid power, but it is possible to power it with solar photovoltaics. The project used Weathertex for the external cladding, which are the first Australian manufacturer to receive a Greentag Platinum certification with a Green Rate R Level A for their natural range products. Additionally, the primed flat cladding and wall panel sheets used have received Gold certification and they meet the requirement set by the Green Building Council of Australia’s Green Star program, achieving maximum rating points for wall cladding and panels.
The House of Häagen-Dazs at its new home at Circular Quay. Photography by Michael Wickham
The building moved from Federation Square to The Rocks in Sydney and sits lightly in its landscape. Once transported to its next destination it will leave no trace of being there.
The biggest challenge was the delivery into the centre of Melbourne CBD and Sydney CBD, which required a reasonable amount of co-ordinations with permits and authorities.
“We had to ensure the building was under 10 tonnes due to the placement at Federation Square as the building was sitting above the train lines and could not exceed this weight,” McCorkell says.
“We were required to come up with an alternative footing system to accommodate this weight requirement.”