The Green, a recently completed five-storey timber frame apartment building by Australand in Melbourne, heralds a new era of affordable building construction for Australia’s medium-density housing needs.
The Green residential apartment complex in Parkville, an inner-northern suburb of Melbourne, has the appearance of a traditional, rendered, multi-level building – but there are few ‘traditional’ elements in this cutting-edge development, which is the first five-storey timber framed building in Australia. It is developed and built by Australand using its ‘hybrid’ construction methodology that combines commercial disciplines with a domestic trade base.
At the heart of this development are numerous design and material innovations, all interlinked to provide a faster and more efficient construction methodology.
The fundamental design principles owe more to conventional detached housing construction than multi-level building techniques, enhanced by an inventive array of prefabricated components.
The entire building took approximately 12 months to complete, according to Australand’s Estimating Manager Kase Jong.
Using a timber frame design based on a ‘structure first’ approach, which considers the engineering capacities of timber to define design parameters, the building was constructed in layers, with the floor of each level ‘dropped in’ using largely prefabricated flooring cassettes.
The largest pre-assembled flooring cassettes used in The Green were sized up to 2.7m x 8m each and weighed just over a tonne.
“The beauty of what we do is that after we have set the floors down, there is no propping of any sort required underneath because the floors span from load-bearing wall to load-bearing wall,” Kase Jong says.
“And because all the internal walls are installed at each level, we are able to come in on the floor below and start roughing in all the services while work continues on the floor above.”
In addition to roughing in services, workers were also able to install walling systems while the structure of the levels above were being completed. Kase Jong says most walls were made using prefabricated frames of 3.6m lengths, which were easy to work with and manoeuvre, before frames were enclosed with full walling systems on site.
Walls included the new Exsulite®-Kooltherm® Thermal Façade System, which Kase Jong describes as a rigid cladding system with a high performance thermoset insulation core, fixed to the timber framing with metal or timber battens.
Developed jointly by Kingspan Insulation and Dulux® AcraTex®, Exsulite®-Kooltherm® Thermal Façade System is a proprietary CodeMark-accredited walling product that includes high-performance insulation characteristics, lightweight rigidity, and outstanding thermal efficiency.
The Kooltherm® K5 boards in the Exsulite®-Kooltherm® Thermal Façade System are fixed and coated with Dulux® AcraTex® weatherproof coating system. The Exsulite®-Kooltherm®Thermal Façade System helps buildings achieve exceptional thermal efficiency, achieving RT4.6 in a timber-framed wall, with a 20 mm cavity, using just 80 mm of Kingspan Kooltherm® K5 External Wall Board and no added wall batts. Total system R-values of up to RT7.0 (heat flow in) can be achieved by adding R2.5 wall batts. Australand confirm that apartments in The Green have an average performance rating of 7 Stars. High-performance glazing (10.38mm) also enhances acoustic and energy efficiency.
THE FUTURE IS PREFABRICATED
According to Kase Jong, benefits and savings associated with the use of prefabricated technologies and building techniques are significant, allowing for greater design flexibility, ease and speed of installation, and excellent thermal and acoustic performance. Interestingly, hybrid buildings are more labour intensive in terms of manpower than those associated with a concrete-based construction of similar scale; the real savings are derived by extracting the cost benefits of engaging the domestic labour force and supply chain to deliver hybrid buildings.
Furthermore speed in construction and reduced materials costs, enhanced by superior performance from new-generation products and building systems. (Labour costs will inevitably fall as greater levels of prefabrication are adopted.)
“All the cladding in these kinds of projects is applied on site at this stage,” Kase Jong says. “Which means the next step is to look at pre-cladded systems. I believe we’re not far from it, but hybrid construction is taking baby steps at the moment.”
Another important feature of prefabrication is worker safety.
Hazards associated with the construction of floor joists, for instance, are mostly averted through the use of ‘drop in’ floor cassettes, which have a direct positive effect on worksite safety.
This level of safety will only be improved as more complete prefabricated units, including full walling systems such as the Exsulite®-Kooltherm® Thermal Façade System, are more commonly used in the Australian market.
“We are happy to work with subcontractors or suppliers that can come up with suitable systems for us,” Kase Jong says.
“For Australand, hybrid building construction methods apply to about 50% of our medium-density houses/apartments. It’s about finding the right solution to the right site for each situation. Our goal and our preference has always been to introduce more 5 storey timber buildings in the designated activity centers in the middle and hopefully outer suburbs. We believe this approach to the construction of these homes makes sites viable that weren’t previously viable from an economic point of view.” “This enables Australand to provide more affordable housing for the average Australian in the middle suburbs where concrete construction is not economically viable. This saving will revolutionise the supply of medium rise apartments in the middle to outer ring suburbs as it creates a price point that people can afford to buy.”