The skyline of Zanzibar will gain a dramatic new addition over the next few years, with the planned opening of the 96-metre high “Burj Zanzibar”. The remarkable feature of this building is not its height, however – but that fact that it will be made largely of wood.
The “landmark project” is intended to “showcase to the world” the benefits of using timber as a construction material, says Milan Heilmann, project manager at CPS Zanzibar, the company behind the tower. While elements of the foundations and core of the building will use concrete, the rest of the structure will be built with timber.
The Burj Zanzibar is planned to be the tallest timber building in the world (although it may be beaten to this title by other projects currently on the drawing board). Construction is set to start next year, and will take three to four years to complete, Heilmann tells us.
Heilmann hopes that Zanzibar’s new wooden skyscraper will be the first of many such projects in Africa. “Our vision is to build millions and millions of homes,” he says. Indeed, increasing the use of timber in the construction industry is seen by advocates as a key step towards combatting Africa’s housing crisis, as well as reducing the construction industry’s massive carbon footprint.
Wood, perhaps the most widely used house-building material throughout human history, is enjoying a renaissance. The Burj Zanzibar is one of several high-profile projects around the world that are either planned or have already been completed.
Swedish company EcoDataCenter built the world’s first wooden data centre in 2018, while lower-league English football club Forest Green Rovers broke ground on a new wooden stadium earlier this year. Other major projects in Africa include the planned Gabon Sovereign Wealth Tower, which will offer 9,000 square metres of floor space in Libreville.
Modern timber-based buildings typically use engineered wood products known as “mass timber”, in which multiple layers of wood are joined together to provide strength. One of the most common mass timber products is cross-laminated timber, in which layers of wood are glued together, with the boards in each layer laid perpendicular to the boards in the layers above and below.
The resurgence of interest in timber reflects the environmental damage caused by materials such as steel and concrete. An estimated 11% of global carbon emissions are associated with building materials.
Research published last year by the International Institute for Environment and Development found that using wood in 50% of new buildings in Africa would result in the continent’s construction sector achieving net negative carbon emissions by 2050.
One of the benefits, in theory, of increasing the use of timber is that it will encourage the planting of new forests, which then absorb carbon and provide a habitat for biodiversity. “Commercial forestry can actually contribute to more conservation and more forest cover if done sustainably”, says Judith Syokau, senior programme officer for commercial forestry at Gatsby Africa, a charitable foundation.
The good news, particularly in East Africa, is that there is currently no shortage of timber supplied from forests certified by the Forestry Stewardship Council (FSC), which operates the best-known certification scheme in the sector.
“There is plentiful FSC-certified timber in the region,” says Caroline Ray, the regional director for East Africa at Arup, a company that designs and plans infrastructure and construction projects. She notes that Uganda and Tanzania provide “robust, sustainable plantations”, from which timber can be exported to Kenya and other neighbouring countries.
Africa certainly has the potential to meet its demand for timber from the continent’s own resources, particularly given that the growing cycles of trees in equatorial parts of Africa are among the fastest in the world. But other elements of the timber value chain are much less well-developed on the continent.
Timber needs to go through several stages of processing before it can be used in construction. “Going from the tree, through to something that’s ready for use in construction, is probably four or five steps,” says Ray. A major “pinch point” in Africa, she says, is the lack of local kiln drying capacity. Kiln drying is needed to remove moisture from timber to prevent the product from warping.
Indeed, Heilmann tells us CPS Zanzibar currently imports mass timber products, which are used for structural load-bearing elements of construction, from Europe. “You can imagine all the logistics that we have to consider when it comes to transport,” he says, adding that increased local timber processing capacity is key to enable timber to be used more widely in construction in Africa.
Even so, Heilmann says that timber is already competitive on cost when compared to conventional materials. While concrete and steel are somewhat cheaper than mass timber at present, using prefabricated timber can significantly speed up construction and thereby lower costs, he says.
“One of the major advantages of timber construction is the elements are prefabricated in a factory,” he tells us, noting that using prefabricated timber could allow a developer to reduce the construction time on a three to four storey building by six to 12 months.
A modern material?
Despite some apparently compelling advantages to using timber, many observers are cautious about predicting that timber will catch on. Scaling up the use of timber in the continent’s construction sector “could take quite some time” says Syokau. “The biggest challenge to mass adoption is perception”, she adds.
Some of the main question marks are around the ability of timber to withstand fires and other hazards. The idea that wood can really match the strength and durability of steel and concrete is simply not easy for many potential homeowners to believe.
In fact, there is ample evidence that well-built wooden structures can be exceptionally resilient. Parts of the Hōryū-ji temple in Japan, believed to be the world’s oldest wooden building, have been standing for around 1,300 years.
Timber can actually offer protection against fire, since outer layers become charred when burnt; the char can then provide insulation to delay the burning of inner layers. While regulators are taking different approaches to fire safety regulation in different jurisdiction, experts agree that ensuring safety requires the rigorous enforcement of construction standards.
Ray notes that authorities in Africa need to improve their understanding of mass timber in order to enable the safe use of the product on the continent. “There needs to be willingness on the government side to be able to really drill down into the details and put in place the appropriate regulations to try and make sure that it is robust and safe,” she says.
Heilmann, meanwhile, acknowledges that timber has to overcome its perceived status as a pre-modern material that is still associated with poverty in the minds of many people. He insists, however, that timber is actually a “luxury material” – and he is convinced that the mass market will soon recognise the benefits.
On Zanzibar at least, timber will literally be hard to ignore once the continent’s new wooden skyscraper rises up on the waterfront. “The more houses and homes are being built with timber, the more people understand the beauty of it,” says Heilmann. “Seeing is believing.”
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