Timber gains traction in sub-Saharan Africa as CLT demand rises

By Joy Crane

The African construction sector is witnessing a significant shift toward sustainable building materials, with cross-laminated timber (CLT) a frontrunner in the transition to green construction. Researchers at the Universities of Stellenbosch and Pretoria point to mounting environmental concerns and climate adaptation needs as drivers of this transformation.

CLT, an engineered wood product known for its structural strength and environmental benefits, is gaining particular attention in the South African market. The material's ability to sequester carbon, combined with its low embodied energy compared to conventional materials like steel, bricks and cement, is gradually attracting commercial and residential developers.

"We're seeing a fundamental change in how African developers and architects approach material selection. The focus has moved beyond operational energy efficiency to considering the entire lifecycle impact of building materials," says Leander Moons of OMT Architects. 

The gluelam trusses were precision engineered at Holzbau Hess in Windhoek

BURJ Zanzibar

Most notably, the versatility of mass timber is recognised in the ambitious BURJ Zanzibar development. Following the worldwide trend of constructing large timber buildings, the 28-storey BURJ Zanzibar will be Africa's tallest hybrid timber building. At its core is a conventional steel-reinforced concrete structure surrounded by glue-laminated timber columns and beams, and modular CLT panels for floors, walls and ceilings. 

Moons and OMT are the architects. He says the timber tower building will promote mass timber manufactured from sustainably managed African plantation timber as the future building material. 

"Plantation forestry is expanding in East Africa. However, presently, there are not enough sawmills in East Africa producing kiln-dried and graded timber for CLT production", Moons explains. 

DfMA

A significant advantage of building with CLT is its compatibility with computer-aided design and manufacturing software that promotes a just-in-time construction process. The Design for Manufacturing and Assembly (DfMA) approach redefines the construction landscape, particularly in mass timber projects. Focusing on sustainability, precision, and efficiency, it also focuses on standardisation and prefabrication. 

The. construction used 14,000 dowels and 25,000 screws.
Pic by Joy Crane

The system streamlines workflows, reduces errors, and accelerates project timelines. Research shows DfMA can cut project costs by up to 37% and reduce assembly time by 62% (www.civilengineer.org). 

In its Built Environment Report 2022-2023, Arup states, "Digital technology and data are transforming how we design and engineer buildings, enabling a deeper level of insight and allowing us to reduce operating costs and optimise the life of buildings. Embedding real-time data also provides our clients with valuable metrics to optimise the in-use performance of their assets". 

Tools like Building information modelling (BIM) improve and speed up construction because project managers, architects, engineers and trades collaborate seamlessly to optimise the allocation of resources and minimise wastage.

84 Harrington Street

A street view of 84 Harrington street during the construction phase.
Pic by Joy Crane

A groundbreaking example of the change in thinking in construction is 84 Harrington Street in Cape Town's District Six. It demonstrates how existing structures can be repurposed instead of demolished. The gloomy and musty building has transformed into a modern multi-use hotel and apartments with restaurants, a swimming pool deck and bar, and a commercial ground floor.

The development, now known as Neighbourgood, is South Africa's first mass timber retrofit and the world's tallest hemp building, featuring hempcrete blocks and hemp-based panels in its interior walls. The speed of adding three floors onto the six-storey building was unprecedented, and the combination of mass timber with hemp-based materials set new standards for sustainable building practices in Africa.

The professional team included Wolf and Wolf Architects, Moroff & Partners Consulting Engineers, Hulme & Associates Consulting Structural and Civil Engineers, R+N Master Builders, Holzbau Hess and Pirmin Jung.

The developer approached Christian Hess of Holzbau Hess to design and manufacture the engineered trusses and timber for the project.

Christian Hess and Dr Johann van der Merwe of Pretoria University on the eighth floor of 84 Harrington Street.
Pic by Joy Crane

Using the latest BIM and DfMA software, Hess spent a month in Germany with Pirmin Jung's timber engineers designing and specifying the project. It included:

"We over-engineered all dimensions by 40mm on both sides to encapsulate the connectors and enhance the safety and quality of the construction," Hess explains.

The CLT and laminated trusses were manufactured in Cape Town. It took two weeks to prepare the truss components and to transport them to Hess' factory in Windhoek, Namibia. The beams were sized, shaped, and drilled on his large Homag WBS140 CNC machine. 

Laser cut steel plates join the old and new structures

The components travelled back to Cape Town for assembly into 5m x 14m long beams at MTO's premises in Retreat. When the trusses were ready, they were loaded onto a truck for delivery to the site.

However, at that point, red tape and the elements put a spanner in the works. It took three days for the municipality to re-approve the route for the abnormally wide load and the temporary closure of Harrison Street. When the truck arrived, a 220-ton crane was ready to lift the massive trusses onto the building; however, six days of strong to gale-force winds made it impossible. 

Although the delays were frustrating for the installation teams, Hess says his 20 years of experience and careful planning for all contingencies kept the project on track. 

He highly values expertise and experience when working with mass timber. "When you connect timber to an existing building, there are always anomalies, and you must be ready for them. The materials are precisely engineered and pre-assembled, leaving little room for error, and the artisan must be able to identify problems like out-of-square existing concrete walls and solve them", Hess explains. 

Increased demand

In research towards his master's degree in architecture at the University of Pretoria, Mishau Azar found a growing interest in the adaptive reuse of inner-city buildings like the Harrington Street development.

"Respondents to my questionnaire identified various benefits of mass timber, including reduced foundation size, speed of construction and the precision offered by CNC technology. 

South Africa's two CLT suppliers, XLam and Mass Timber Technologies (MTT) report increasing demand across multiple sectors. 

"The market has evolved significantly over the past few years," notes Marcus van der Hoven, Director of MTT. "We're seeing interest from individual homeowners, commercial developers, and the eco-tourism sector, where sustainable construction aligns perfectly with their brand values. 

Training

On a cautionary note, Hess and Belinda Duncan of Terraverta Habitats assert that mass timber on-site installation teams need specialist training. The scale of the timber and size of the connectors differ from those used in joinery and furniture manufacturing. Hess believes it is essential for installation teams to be exposed to and mentored by international best practices. 

Time to build with timber

Sawn timber, a locally grown, sustainable resource, provides the raw material for the construction of timber frame buildings using cutting edge cross-laminated-timber technology to lock in carbon and minimise environmental impacts.

How engineered wood can decarbonise the South African built environment …
by Roy Southey, Executive Director, Sawmilling South Africa

Our planet is faced with both an environmental crisis and housing crisis. There is, however, a sector that is overlooked as a viable, renewable and long-term solution to climate change and urbanisation.

Having recently attended the annual Wood Conference in Cape Town, I was inspired to hear and see how timber is being used successfully in the built environment, not just in the northern hemisphere but also on home soil. From modern homes in an off-the-grid community in Mogale City to a learning centre in the Drakensberg, from a new home in Knysna or a rooftop extension to a Johannesburg home to the Green Point Education dome in Cape Town.

At the mention of wood, your mind’s eye might only be able to conjure an image of a log cabin or “wendy house”, or perhaps a roof truss or timber flooring. It’s unlikely that you imagined a multi-storey building made from cross laminated timber (CLT), a type of engineered wood for mass timber construction.

You’re forgiven, considering that less than 1% of new South African houses use timber as the primary construction material. By comparison, some 90% of new houses in New Zealand are made of timber.

As a sector trying to promote the adoption of mass timber, we are faced with a long-held belief that brick-and-mortar is the only way to build homes, schools and clinics. There are many misconceptions, not least of which being strength, durability, fire safety, and cost. Many people view wood as rudimentary or weak.

Mass timber uses technological advancements to engineer wood to have a stronger strength-to-weight ratio. In the case of CLT, thin layers of timber are laid crossways before being bonded and compressed together.

It’s been said that wood isn’t manufactured, it grows. From a South African perspective, the wood is sourced from sustainably managed tree plantations.

Pine timber grown by AC Whitcher in the Western Cape … it’s time has come.

The forest products sector is the only one to have the trifecta of green solutions when it comes to the carbon sequestration by trees in managed forests, carbon storage in its products and the substitution of carbon-intensive materials with wood-based products.

The construction sector accounts for 35-40% of global energy related CO2 emissions, with a large proportion (embodied emissions) attributable to the extraction, processing and energy-intensive manufacturing of building products. The other main source is operational emissions from heating, cooling and power generation.

Timber boasts a significantly lower carbon footprint compared to traditional building materials like concrete and steel. Timber also maintains a carbon-negative status throughout its lifecycle, from initial production to disposal, and it sequesters more carbon than it emits during processing and installation.

Our colleagues at the Stellenbosch University, Prof Brand Wessels and Dr Philip Crafford have published various pieces of research, highlighting the advantages of increased timber use in South Africa. Basic modelling analyses show that if the market share of wood-based buildings increases to 20% of new constructions, the embodied energy and global warming potential of the residential building sector could decrease by 4.9%.

As our population and economic migration increases, there is an urgent need to change how we build high density and single family housing, quickly, cost-effectively and sustainably.

Human friendly, planet friendly, timber is the ideal building material of the past and the future.

There is a climate, economic and even social case for timber, and a significant opportunity for innovation, localisation and employment creation. Several industry players, architects, construction engineers and producers are focused on making engineered wood more accessible to the local market. With this comes the need for upskilling or reskilling, business growth and employment opportunities.

Wood lends itself well to modern, modular and off-site methods of construction, with improved efficiency and performance. Single and multi-storey buildings are prefabricated off-site, allowing for quicker on-site assembly, less journeys to and from site (and the associated carbon emissions), and minimised disruption, dust and noise.

Biased towards tried-and-tested steel and concrete, the public and private sector is reluctant to drive the use of timber in the built environment through procurement policies.

Through initiatives such as the Forestry Master Plan, partnerships with the Department of Trade, Industry and Competition and forward-thinking academia, we want to shift the needle in favour of using locally grown and processed timber.

Both the University of Pretoria and Stellenbosch University have a strong wood science focus, and helping to educate a new generation of architects and construction engineers.

Dr Schalk Grobbelaar, senior lecturer and chairperson of the York Timbers Chair in Wood Structural Engineering in University of Pretoria’s Department of Engineering & Technology Management, is a champion for our cause. He believes that a design-led approach is crucial to successful risk management where timber solutions are used, while also exposing people to possibilities that timber brings.

Dr Grobbelaar’s team has been focusing on traditional timber frame construction combined with modern CNC machined plywood/OSB modular construction.

Prof Wessels and Dr Crafford have also developed The Wood App, a platform that offers architects, builders and designers with access to a host of CPD accredited courses on local wood standards, materials and best practice.

The sawmilling sector, while small in comparison to other industrial sectors, supplies sawn timber and other products for various applications, from structural timber to moulded and machined products for decking, flooring and ceilings. Many of these sawmills operate in rural or peri-urban areas, providing much-needed employment to thousands.

The uptake of timber represents a massive opportunity for our country and our planet. It’s time to trust in timber.

Illegally treated timber seized

  • Timber poles being loaded into a pressure vessel for preservative treatment.

Arch Wood Protection South Africa has praised the National Regulator for Compulsory Specification (NRCS) for seizing R1 million worth of illegally treated timber, describing it as a big win for the treated timber industry.

“We are pleased to see the regulator taking such a firm stand on illegally treated timber that is currently flooding the market as a cheaper alternative to quality pressure treated timber. This is a big step forward in protecting the industry and all its stakeholders against substandard products,” said JJ du Plessis, senior business manager at Arch Wood Protection South Africa.

Du Plessis said that the industry has always strived to introduce robust standards that protect the end-user, but over the last few years they have seen increasing levels of activity by groups that choose to operate outside the standards and regulations that govern the industry. This, he said, has caused substantial reputational damage to the timber industry.

“We want to also commend the South African Wood Preservers Association (SAWPA) and the NRCS for ensuring ongoing collaboration to ensure that treated timber remains part of a sustainable way forward in South Africa. This multi-pronged collaboration amongst important stakeholders will ensure that high quality remains the hallmark of our industry,” said du Plessis.

All wood preservatives used in South Africa must be registered with the Department of Agriculture and comply with the SA National Standards. Use of timber in building construction is also regulated by the Building Regulations, which ensures that it is treated against termite and wood borer attack, as well as fungal decay.

  • Wood that has been properly cured, treated and maintained is good for multiple uses including home building and the construction of high rise buildings.

There is also a National Standard governing wood preservative operations to ensure the safe handling of preservative chemicals to mitigate health and safety and environmental risks.

Three types of preservatives are used in SA; water borne preservatives (e.g. CCA), oil-borne preservatives (e.g. creosote) and light organic solvent borne preservatives.

Compliance with the regulations and national standards ensures that timber sold to consumers is fit for purpose and will last for the duration of its intended lifetime. Use of untreated timber, or poorly treated timber impacts negatively on consumers, and may also pose health, safety and environmental risks.