Above: Aveo Bella Vista Aged-Care – Strongbuild Binderholz.
Wood construction innovation within the building industry has seen timber, one of the oldest building materials known to man, gain traction in multi-storey buildings as developers and designers alike become aware of the structural performance and construction benefits of structural timber building systems.
Cost-effective and sustainable, timber is now an available option in mid-rise building construction thanks to a change in the National Construction Code Volume One (NCC), administered by the Australian Building Codes Board (ABCB). From May 1, 2019 timber buildings (Classes 2 to 9) can be built up to an effective height of 25 metres, typically 8-storeys, under the NCC Deemed-to-Satisfy (DTS) provisions rather than requiring a Performance Solution approach.
These code changes follow the 2016 acceptance of a DTS solution introduced to the NCC permitting, for the first time, construction in fire-protected timber building systems to an effective height of 25m for Class 2 (apartments), 3 (e.g. hotels) and 5 (office) building classifications.
Timber building systems include traditional lightweight timber framing and newer massive timber construction (MTC) options including cross-laminated timber (CLT), laminated veneer lumber (LVL) and glue-laminated timber (glulam).
These initial code changes came about after extensive work and a successful submission by Forest and Wood Products Australia (FWPA), the company behind the WoodSolutions Program.
Ric Sinclair, Managing Director, Forest and Wood Products Australia says the code change was the outcome of a strategy the FWPA adopted some 7 years ago to address the issue of combustibility in the building code, which was seen as biasing the Code against timber.
“It was quite strategic that we were trying to identify what were the changes that we could deliver a safe outcome but reduce any impediments against the use of timber. Through the ABCB’s independent technical review process, our proposed changes were supported because of the solid body of technical evidence that demonstrated our systems, based on fire-resistant grade plasterboard and sprinklers, were safe for occupants and the community.” says Sinclair. “An additional public benefit will be faster project construction over time that will lead to cost savings.”
Boris Iskra, National Codes and Standards Manager, Forest and Wood Products Australia says fire-protected timber (a defined term in the NCC) building elements are fire safe and the NCC permits fire-protected timber building elements (e.g. walls, floors, lift shafts) to be used wherever an element is required to be of non-combustible construction.
“This is because we have demonstrated that fire-protected timber building elements achieve the fire performance requirements of the NCC. Prior to 2016 when the first Code change came through, anyone wanting to build a timber building had to do a fire engineered solution,” explains Iskra. “There were a lot more steps, hurdles, costs and essentially time delays in getting the buildings done. You still have two pathways but with DTS, if you follow the recipe, you’re approved.”
According to the ABCB, the Deemed-to-Satisfy solution follows a set recipe of what, when and how to do something. It uses the DTS Solutions from the NCC, which includes materials, components, design factors and construction methods that, if used, are deemed to meet the performance solution requirements.
The Deemed-to-Satisfy provisions have been extended to include all classes of buildings which will now enable the use of fire-protected timber building systems in aged accommodation, schools, retail and hospitals.
This is good news for building professionals including property developers and builders because the change to the NCC will save time and money compared to demonstrating compliance via Performance Solutions, for getting mid-rise timber building constructions over the line at the approval stage.
“Prior to the DTS solution we were hearing of costs in the order of $30-40K on a project just to undertake a Performance Solution. From the timber perspective, you were behind the eight ball before you even started because you knew there were always these additional costs to contend with,” says Iskra.
Developers and design professionals alike will appreciate the code change, which effectively see Australia lead the rest of the world in terms of the range of building types that can be built.
The tallest wood building in the US is Portland Oregon’s eight-storey Carbon 12 building and the tallest timber building constructed in the world to date is the 18 storey (53 metres) Tall Wood Residence in Vancouver, Canada.
Cess De Jager, President and CEO, Softwood Lumber Board, US says there are a number of misconceptions in the market regarding fire but once the facts are understood, it is not a barrier.
“In North America, light frame construction is common for residential construction and the fire performance of those buildings is well understood. Fire resistance rating requirements are based on construction type and fire separation distance is set out in the US building code (aka International Building Code),” says De Jager. “One hour and two hour fire resistance requirements are generally provided by fire-rated assemblies that include gypsum sheathing.”
In Australia however, the maximum fire resistance level of 4 hours is required in buildings such as warehouses and factories which could be achieved using massive timber building systems.
“We are part of this international revolution that’s occurring with timber construction. We’re seeing significant interest around the world to build taller and safer in timber,” says Sinclair.