In 2013, Melbourne’s Docklands precinct witnessed the opening of Australia’s first modern high-rise building to be constructed out of engineered timber as Lend Lease opened the 10-storey Forte apartment complex built using cross laminated timber (CLT).
Last May, Sydney’s Barangaroo saw completion of the world’s largest commercial office building made out of engineered timber as the International House Sydney constructed from CLT and glue laminated timber (glulam) supported by conventional concrete at ground level opened its doors.
In Brisbane, ground broke in May on another Lend Lease office tower to be built using engineered timber which when complete will rise to 52 metres.
All up, Timber Development Association NSW executive director Andrew Dunn says, the number of modern timber buildings which are equal to or greater than seven storeys in height has risen from none in 2008 to 30 (completed or under construction) now – of which Australia accounts for four. Whilst engineered timber is much talked about, opportunities also exist using traditional timber framing, which he says in Vancouver (Canada) accounts for around 70 per cent of new multi-storey buildings of up to six storeys in height.
In Australia, momentum was further aided in 2016 when for the first time timber buildings of up to 25 metres were allowed under the National Construction Code using a deemed to satisfy solution – albeit with performance solutions being more popular with top tier players because of the flexibility these offer.
According to Eileen Newbury, national program manager for WoodSolutions and national marketing manager at Forest & Wood Products Australia, demand for timber on multi-storey buildings is being driven by several factors. Along with the environmental benefits, developers are increasingly keen on the economic benefits which timber provides in faster project delivery and construction times and lower cost. Along with the likes of Lend Lease and Australand (now Frasers – developer of the five-storey apartment complex The Green in Melbourne’s north), a number of design and engineering firms are jumping on board, she says. All this is being helped along by a growing demand for multi-residential housing as Australia’s population grows.
“All these companies and individuals have got a passion for building and are exceeding client expectations,” Newbury said, referring to the developers, architects and engineers now using engineered timbers. “What they have got in common is that they take advantage of modern technology and they combine streamlined building systems with sustainable resources such as timber. This means they can build faster and more efficiently.
“There is a vast number of companies who are now preparing to escalate their adoption of timber and sawn wood products.”
According to proponents, timber offers numerous advantages.
First, the relatively light weight of the material and ease with which construction using timber is done enables reduced on-site labour requirements, lower costs, safer working environments and lower waste. This is especially the case with large portions of the building being able to be fabricated offsite.
These benefits are significant. In the case of Lend Lease’s Forte apartment complex, on-site assembly of the structure took just three months and required just two apprentices and two tradespeople, Newbury said. When the structure for International House was being erected, Northrop Consulting Engineers Associate Structural Engineer Consulting Ali Habibi said, six workers were required on site. In Canada, the timber frame for the 18-storey timber and concrete hybrid Brock Commons Tallwood House was constructed in just nine weeks.
Moreover, being ‘dry’ sites, building with timber reduces the need for high risk work such as cutting, welding and grinding, along with the need for scaffolding. With a timber building being around 50 per cent lighter compared with their concrete counterparts, the size of the footings needed to support the structure can be reduced.
Citing independent research commissioned by FWPA, Newbury says timber can deliver cost savings of between four and 13 per cent. On The Green, Frasers reckon they cut 20 per cent off the cost through using CLT.
From a structural perspective, Habibi said the lighter weight means buildings constructed with timber do not need such a large foundation. This enables the use of fewer piles or less deep footings (and associated cost advantages). The lighter building frame has greater lateral stability from an earthquake perspective and attracts a lower seismic load, reducing the amount of material required to control the building from a lateral stability viewpoint in an earthquake. Finally, the lighter timber buildings enable costs to be saved on the ‘transfer level’ on the first floor between the units and apartments above and the basement/car park below, where you want a large opening at the entry level of the building.
Beyond this, timber as a natural material also has a ‘warmness’ associated with it. Walk around the Docklands Library (made of CLT and glulam), Newbury says, and you see people admiring the columns.
People feel more comfortable when surrounded by nature, Dunn adds. Walk through the wooden part of International House, he says, and you feel more comfortable compared with the cold and damp feeling associated with the concrete part of the building.
When showing people around the Forte building recently on a 35-degree day, he says the material’s ability to ‘breathe’ and absorb moisture when the air was dense but release it when the air was drier meant a number of the guests when entering the building mistakenly believed that the air conditioning had been running. Whereas the term ‘concrete jungle’ describes an unnatural and less humane environment, Dunn says architects have occasionally observed people ‘hugging’ timber columns.
That points to further benefits and possible impacts upon human health. In a review of studies published in 2015, Planet Ark noted that wood has been shown to have positive physiological and psychological benefits. The feelings of warmth and comfort that wood elicits in people lowers blood pressure and heart rates, reducing stress and anxiety and increasing positive social interactions, Planet Ark concluded. Wood products within a room have also been shown to improve indoor air quality by moderating humidity.
Along with residential and commercial buildings, this offers important benefits in settings related to areas such as healthcare, aged care and education.
Finally, proponents of timber point to its environmental benefits, which derive from its status as a natural and renewable material which acts as a store of carbon, has good thermal insulation qualities and is often used relatively close to where it is produced. By using 76 per cent timber as opposed to 100 per cent concrete, Habibi said, designers on the 24-storey HOHO building in Austria saved around 2,800 tonnes of carbon – equivalent to car running every day at 40 kilometres per hour for 1,300 years or 117,000 cars running together from Sydney to Newcastle.
Naturally, there are limitations.
In the case of CLT, Habibi says, the absence of a well-developed local supply chain has forced builders on early projects to source material from overseas – a process which adds several months to lead time notwithstanding timber’s faster assembly times.
Timber’s more restrictive spans also mean the material is best suited to applications where excessive spans are not needed. As well as residential, this includes hospitals, aged care facilities, schools and student accommodation.
Sawn timber framing, meanwhile, is generally viable up to around six storeys in height, Dunn said. Beyond that, you are looking at engineered timbers or CLT.
Whilst timber is flammable, the material offers one advantage for fire engineers in that it chars at a predictable rate and therefore provides greater certainty about how long occupants have to escape prior to structural collapse (unlike steel reinforced concrete which is prone to sudden collapse). That said, Newbury, Habibi and Dunn all stress that the critical issue in respect of fire safety is not so much the structural material used but rather the individual fire engineering solution for the building in question.
Finally, educating an industry which has worked with concrete on multi-storey projects to work with timber instead will be a gradual process, as will persuading industry participants to step away from the known environment of concrete to the unknown one of timber.
When working with timber, Dunn advises architects to engage with builders and suppliers early in the project and to design ‘for assembly.’ Since penetrations in timber beams work slightly differently compared with those in concrete, Habibi adds that it is important to liaise with services engineers.
Finally, Dunn points out that use of timber in multi-storey buildings is not new and was once commonplace. Indeed, he says, he often shows images of a six-storey timber frame apartment in France which dates back to the 13th century.
“There are a heap of buildings in Australia and in the world that are seven stories or greater and have been around for hundreds of years,” he said. “It’s just re-finding old ways of building with modern products.”