Can you imagine a building that soars to 24 storeys, comprising 75% wood? No need to imagine it – it exists. The HoHo Tower in Vienna, Austria, at 84 metres, is one of the tallest timber buildings in the world.
Completed in 2019, the building combines mass timber with concrete cores, exemplifying hybrid construction methods. It serves as a mixed-use building with residential, office and commercial spaces. And where does such wood come from? Sustainably managed forests or farmed trees, or plantations.
“At the mention of timber buildings, one would probably conjure images of ‘Wendy houses’ or log cabins,” said Roy Southey, executive director of Sawmilling South Africa (SSA).
While wood is used to build rudimentary structures, there is a growing trend of using mass timber in high-rise buildings, functional spaces and retro-fits for homes. The developments are driven by the need for more sustainable construction methods that reduce carbon footprints and enhance environmental resilience.
As engineering and building techniques continue to evolve, mass timber is likely to play an increasingly prominent role in construction. There are several projects on home soil as examples, from modern homes to a learning centre in the Drakensberg, from a new home in Glencairn or a rooftop extension to a Johannesburg home, to the Green Point Education dome in Cape Town.
Contrary to commonly held beliefs, the consumption of sustainable wood protects our indigenous forests. Well-managed plantations reduce soil erosion, maintain the water balance in the surrounding areas and provide refuge for an array of species.
South Africa’s 1.2 million hectares of farmed trees are planted, harvested and replanted for the purpose of making sawn timber, pulp and paper products, building and agricultural poles, among other things. When a harvested tree is made into a solid wood product or pulp for paper, the carbon remains locked up in those products. When the land is replanted with new trees, the carbon cycle begins all over again. Some 0.9 tonnes of carbon are stored by one cubic metre of wood throughout its lifetime.
“This is why the procurement of renewable, sustainably produced wood by the construction sector holds the greatest potential for climate change mitigation," Southey noted.
South Africa has traditionally relied on brick and mortar for building, but this is slowly starting to shift, says Southey: “There is an exciting move by architects as they look to the forest products sector for carbon-neutral and renewable options.”
Timber competes well with concrete and steel, in that it offers strength, can withstand seismic activity, and is much lighter to transport.
“Timber structures are also often prefabricated off-site, reducing both the construction times and associated costs,” he noted, adding that timber is being used with concrete cores to create hybrid buildings, as the HoHo Tower demonstrates. South Africans have, in many ways, been conditioned to believe that building with brick and mortar is the only way.
Timber would find ideal application in helping to address South Africa's housing crisis. “It is light, easy to transport and lends itself to rapid assembly,” says Southey. Timber-frame homes can be mass produced in panel form, transported to site and put together by a construction team. This in turn provides opportunity for upskilling and job opportunities. In addition, existing office buildings especially in city centres could be adapted to create living environments.
According to Forestry South Africa, The South African forestry and forest product sector employs 158 000 people, with 690 000 people dependent on it for their livelihoods. With an export value of around R38.4 billion, it is a key contributor to South Africa’s economy. Increasing the use of wood in construction could significantly enhance the sector's economic contribution to South Africa.
“In the end, it is about keeping sawmills in business, educating architects and construction professionals, and of course, consumers about the good in the wood. Our country is ripe to tap into the hidden potential of a renewable and functional material,” concluded Southey.