As the push to use materials which are friendlier to the environment and safer, faster, easier and less costly to build with gathers pace, a movement toward more extensive use of timber as a structural material in commercial and multi-residential buildings in Australia continues to expand.
Throughout the world, designers working with timber on multi-storey buildings are reaching for the sky. In May, Vancouver architect Michael Green unveiled a proposal for the world’s tallest timber building in Paris. The 35-storey tower, known as Baobab, would comprise a mix of market and social housing, a student hotel and urban agriculture. Other 30 storey buildings made from wood are planned in Stockholm, Vancouver and Vienna.
Locally, proposed changes to the Building Code of Australia would allow for timber building systems to be used in offices, hotels and apartment buildings of up to 25 metres (approximately eight storeys) in effective height – up from the current restriction of three storeys.
Enthusiasm within the industry is growing. In 2013, Andrew Lawrence, a structural engineer and associate at Arup, wrote that he would be “perfectly happy to live in a twenty storey timber building.”
Primarily, all this is being driven by a push toward greater levels of sustainability, Melbourne-based senior project management consultant and chair of engineered timber floor frame systems outfit TECHBUILD Jack Haber says. Describing sustainability as the “one unassailable thing that timber can claim over all other building materials,” Haber said trees were natural, were a good natural way to effectively store carbon, and did not involve carbon intensive processes in production.
“In an environment that we are in at the moment…it is inevitable that embodied energy is going to become a factor that builders have to consider (in Australia) as they have to consider it in Europe,” Haber said.
“There is an overwhelming understanding and acceptance that timber is a more sustainable product and that greenhouse gas emissions are far fewer with a timber building than what they are with a concrete or steel building.”
Outside of sustainability, Haber says timber’s relative light weight makes it easier, safer, faster and less costly to build with compared with traditional concrete. Panelised timber construction is also easy to work with at heights, making it ideal when adding floors to existing buildings.
Timber is also suitable in some circumstances where conditions are less than favourable. At Docklands, where all buildings have to be piled, for example, footings under Lend Lease’s Forte apartment complex were much less onerous than those built with concrete in the same area.
Finally, many of those who work with timber hail largely from the residential sector and are therefore less likely to be unionised compared with their concrete or steel sector counterparts. This reduces the potential for industrial disruption on site.
Of course, a critical question when it comes to timber revolves around fears surrounding fire resistance and safety. In the UK, such fears were exacerbated in June when five homes were destroyed and 30 were damaged after what started as a small fire on the first floor of a four-storey timber frame block of flats in the city of Canterbury spread upwardly and ferociously. Kent Fire and Rescue Service assistant director Paul Flaherty said the timber framed construction had enabled the fire to spread quickly among the frame voids.
Naturally, timber suppliers acknowledge that wood does burn but suggest that in some respects, it can outperform steel in terms of the length of time it can be exposed to fire without its structural integrity being compromised. Whereas wood burns slowly and char created on the wood surface as it burns helps maintain the integrity of the structure, UK-based timber products supplier International Timber argues, metal will melt upon reaching a critical temperature (approximately 1,300 degrees Celsius) and collapse.
Haber says timber can also has a set of coatings which help stop it from burning, and that especially with mass wood such as CLT or solid timber beams, these will have to be exposed to fire for a considerable length of time before they start to collapse.
Perhaps the biggest challenge for tall timber, Haber says, revolves around a lack of awareness amongst architects and engineers about its potential as a material in tall buildings. He says the challenge for the timber industry was to spread the word about the potential for wood in such applications.
An additional difficulty in the case of cross laminated timber, he says, is that there are currently no domestic suppliers and those wishing to use it are reliant upon imports. Were a domestic supply chain to develop, he said, managing supply would be easier and costs would fall.
Overall, Haber believes timber use in tall buildings will grow. He says framed timber construction is suitable for buildings of up to five or six storeys, mass timber likewise up to eight or nine and you are looking at a concrete solution after that.
He believes timber buildings are the way of the future in commercial and multi-residential construction.
“If for no other reason – and there are many reasons why it’s a good material – from a sustainability perspective if we want to reduce our greenhouse gas emissions and we are serious about it, then timber buildings are a must,” he said.