Prefab and timber: the great green convergence
Sponsored: WoodSolutions | 20 December 2016
The growing momentum around prefabrication and the market’s growing appetite for lightweight and massive timber building systems in larger commercial and residential projects is creating a solid pathway to achieving more sustainable, low-carbon structures in the built environment, according to Ric Sinclair, managing director of Forest and Wood Products Australia.
Sinclair says the current industry excitement around the use of wood products in prefabrication comes down to three factors.
First, wood is a sustainable product. A well-managed forest is a renewable resource, and timber stores carbon both as it grows and once it is used.
Second, prefabrication increases the speed and safety of construction.
Finally, prefab offers the opportunity for offsite manufacture.
“What makes wood special is other materials can be used for faster construction and offsite construction, but only wood does all of these things,” Sinclair says.
“Wood is where the three come together.”
Another aspect of using timber, including the engineered timbers, is the accuracy of processing that is possible with prefabrication, he says.
With computer-aided drawing and computer-aided manufacture (CAD-CAM), it is possible to fabricate to within a millimetre. This is achievable with timber building systems and steel, but Sinclair says it is difficult to do with concrete.
FWPA is one of the industry bodies that form part of the new Australian Research Council for Training in Advanced Manufacturing of Prefabricated Housing, based at the University of Melbourne.
Sinclair says prefabrication can address the lack of skills that is responsible for the building sector’s sometimes poor performance in terms of defects, compliance and quality outcomes.
Controlled manufacture, automation and stepped processing can all help, he says.
One of the legacy issues wood products have had competing with steel and concrete has been their less homogenous nature.
Steel, concrete and other materials are the result of known chemical and industrial processes, and are well understood by engineers in terms of performance standards and capabilities.
Now engineered timber levels the playing field
Timber, however varies, both between species and from log to log. This is where the new generation of engineered timber products level the playing field.
“There is a growing alphabet of engineered timber products,” Sinclair says.
They include laminated veneer lumber (LVL), cross laminated timbers (CLT), glulam, laminated strand lumber (LSL) and plywood.
The performance of engineered timber products is more consistent and predictable than most traditional timber alternatives. The process of modification removes the variability and increases the ease of engineering and handling.
It’s still a natural product, he says, but modification makes it more of a known quantity in terms of performance standards.
“These types of products are not new – plywood is an engineered product that has been around for hundreds of years.”
The continued expansion of engineered timbers is exciting, Sinclair says, as it creates more opportunities for using them.
“These products are compelling, competing and convertible.”
The market is growing rapidly
The number of companies using prefabricated approaches with timber is growing rapidly. They include Lendlease, Strongbuild, architect-led builder ARKit and Timber Building Systems – a company founded by the former managing director of Hickory’s Unitised Building division.
ARKit director Craig Chatman says the company is using two main methods for prefabricated construction – modular and panellised building.
“Using the modular system we deliver building works in the factory that are 90 to 95 per cent complete. With panellised construction we build wall, floor and roof elements as a series of cassettes, complete with plumbing, structural framing, insulation and linings.
“These components are fabricated in the factory and assembled on site. Prefabricated components combine the time and quality benefits of offsite construction, whilst not constraining the design to transportable, module sizes.”
Chatman says that prefabricated construction requires upfront consideration of the build method to inform early design decisions. That means there is alink between design and construction that provides opportunities to explore innovative options, building methods and the best construction sequence.
The company’s projects include both residential and commercial projects constructed from timber products. One of its residential projects, The Light House, was a finalist in the Australian Timber Design Awards.
Chatman says the company has chosen to focus on using timber because it is “the ideal product for prefabricated construction”.
“It offers significant design flexibility and, as a lightweight building system, delivers a better environmental outcome.”
He says they use a range of products, preferring suppliers and materials with strong environmental credentials. These include products that are formaldehyde-free or low-VOC, use recycled content or have PEFC or FSC certification.
“This information is becoming more prevalent in the market and assists us in making informed selections.” Chatman says.
The engineering considerations for timber in prefab are no different to steel, he says, and clients have been very positive about accepting timber construction.
“The environmental, time and cost benefits of using timber are seen as a considerable advantage over the use of steel or masonry construction.”