The Rands and cents of timber construction

The advantages that come with using timber in construction are numerous and while there are clear, refutable misconceptions relating to this building material in South Africa, views around its affordability – and potential for affordability – as a construction material are varied.

By Jennifer Rees, Director of Haas&DAS Communications.

The most commonly held misconceptions among consumers and some facets of the construction trade are that timber construction has questionable strength and longevity, can easily catch fire, burns quickly and is susceptible to rot.

Much to the contrary, says Werner Slabbert Snr of Rustic Homes, Cape Town-based timber construction company: “People often ask me how long a timber home will last and how it might perform under fire conditions. Built to standard, in line with the National Building Regulations and SANS 10082 for Timber Frame Buildings, and properly maintained, a timber structure’s longevity can be indefinite. It performs well – and predictably – under fire conditions and built correctly, a timber structure offers the same safety standards as any other type of structure and will not rot.”

Beach house vs. Wendy house

Interestingly, dichotomous perceptions around timber’s affordability as a construction material are emergent; that is that it is either very costly and reserved only for the monied or that it is a cheap and unreliable alternative to traditional brick and mortar construction.

Stephan Jooste, WoodEX for Africa Organiser and Owner of EasyClip, alludes to the possible reasons for this split view of timber frame building: “Some people believe timber as a building material is expensive and others believe it is cheap; the classic comparison of the lavish beach house versus the Wendy house applies,” he says, noting, “Timber is a very versatile product that can find a home in more and less cost-effective structures; how the structure is built is the determining factor and the extent to which consumers will understand and accept the methodology will dictate its uptake. In the USA, timber frame homes are very common, because they can be built more affordably, and the market fully embraces timber construction as a perfectly sound building method.”

Jacques Cronje of Jacques Cronje Timber Design, experiences consumer perception in South Africa as regarding timber construction as an affordable building material, while he believes otherwise. “I think the misconception of timber’s affordability may stem from a time in the ‘60s and ‘70s when cheap timber holiday homes were built along the coast. Many of these had very thin cladding, no insulation and bear no resemblance to the high quality, well-insulated timber homes we build today, especially since the introduction of the SANS 10400 section XA governing energy usage in buildings and which calls for minimum insulation standards.”

“Where a timber home can be more affordable than ‘traditional’ building materials is when, for example, it is built on a suspended timber floor structure on a steep site, due to the fact that foundations for conventional brick buildings become much more expensive on steep sites. Similarly, timber homes can also be less costly than brick and mortar on other inaccessible sites; almost the entire home’s worth of materials can be delivered on one truck load, compared to the many deliveries the heavier materials required for a brick home would necessitate,” he adds.

Barriers to market entry

George Dowse, Processing and Product Development Researcher at Hans Merensky, speaks to possible barriers to market entry for timber construction, pinpointing historical legacy, general culture, and educational deficits as contributing factors. “Historically, South African construction is based on the old English and Dutch styles of brick and mortar, whose subsequent mainstream status in South Africa today supports the current attitude towards these building materials as the most prominent – if not the only – materials with which to build. South Africans simply do not yet have the ‘timber culture’ for everyday consumers to understand and appreciate not only the primary benefits of this material for home building, but the broader environmental and economic benefits that a society actively engaged in using timber products can enjoy.”

“Further to this, engineers in South Africa are not extensively taught how to engineer with wood; timber structures and properties make up only a fraction of tertiary course work, which results in successive generations of engineers prescribing a material with which they are more familiar (like steel, brick or concrete), even if a customer requests that timber be used,” comments Dowse.

Limitations of timber construction

According to Cronje, “There are very few limitations when it comes to timber construction and as technology evolves, these are becoming even fewer. In South Africa, SANS 10082, governing timber frame building, limits the height of a timber building to single- and double-storey timber homes; any taller than this, and the project will be deemed a ‘rational design’ which needs to be structurally designed and signed off by an engineer.”

“Further limitations of timber construction include building into the earth (such as with basements, which need to be executed in concrete or brickwork) and building on a common boundary, due to fire regulations. In tall timber buildings, the fire escape and lift shafts are typically still done in concrete, but this is really a minor ‘limitation’ in the use of timber.”

Slabbert notes, “SA Pine structural timber is available in up to 6.6 metre lengths, restricting very long spans with a single piece of timber. That said, engineered beams, like laminated timber beams or I-beams can span much longer lengths, but will come in at a higher cost.”

“Skilled labour is required to build timber structure as opposed to brick and mortar,” says Slabbert, explaining, “Brick-laying or wet works can be learned fairly quickly and easily, but the art of carpentry is taken up through a longer, more tedious schooling process, resulting in a higher cost of labour.”

Economies of scale: Challenges and the route to affordability

According to Dowse, building a well-designed and approved timber building in South Africa in the current climate will come at a slightly higher cost than brick and mortar may. “This is because we do not have the economies of scale yet and low volumes come with various price influences, including, among others, the availability of timber components required for optimal building,” he says.

“With around 80% of all structural timber produced in South Africa going to roof trusses, it is not economically feasible to produce the full range of products without supporting sales volumes. In the USA, for example, there are four or five different structural grades available for South Africa’s two, and almost double the number of dimensional combinations. In South Africa, however, requiring a 120 mm-wide component, for example, would necessitate over-design due to being limited to choosing either a 114 mm or a 152 mm component,” Dowse reasons.

“The same is true for engineered products like cross laminated timber (CLT), veneer boards and glulam. The first CLT manufacturing plant in South Africa is only now starting up in Cape Town with low volumes. These manufacturing plants require big capital investment and therefore large sales volumes to keep the production and other costs at an affordable level; without a steady timber building market this is difficult to maintain. The alternative, is to import these products (which is happening). This, depending on the exchange rate, can add further to the production costs.”

But for both Jooste and Slabbert, rather than augmenting supply or demand, offering an innovative alternative to the traditional timber structure, prefabrication could play a key role in making timber construction more accessible to the general housing market.

timber construction

Rather than augmenting supply or demand, offering an innovative alternative to the traditional timber structure, prefabrication could play a key role in making timber construction more accessible to the general housing market.

“Other than with brick and mortar, so much of timber frame can be premanufactured, which is especially important when building in remote locations. Timber is very amenable to scalability, offers a lower construction footprint and requires less work and time on site; an entire structure could be manufactured in a warehouse, shipped to site and erected quickly, anywhere in the world and with the minimum tools,” says Jooste.

Slabbert confirms, “Timber is so versatile and, coupled with prefabrication, it can quickly, easily and affordably go a long way to address South Africa’s housing backlog. Scalability in the delivery of quality affordable timber housing will be determined by prefabrication, and while timber may not necessarily become a cheaper building material, the way we engineer and deliver the product in future could be a game changer for affordability.”

The hybrid home: A viable compromise

Comparative studies, marketing materials and discussions on various building materials can lead to ‘either-or’ rationales around which building materials to use, which can quickly close the door on the many benefits of ‘hybrid’ construction.

For Jooste, “Timber as a building material is well positioned to complement brick and mortar; they can work well together to respond intelligently to a client brief.” Cronje concurs: “In my own projects, I often, due to preference, mix timber with other methods of construction, using each material type to its best ‘fit for purpose’.”

Timber has remarkable potential in South Africa – and has been proven across the world – to add cost-effectiveness to its ample range of benefits. Designed and built to standard by qualified and registered persons who are experts in timber engineering, construction and inspection, timber construction is as strong, durable and long-lasting as any of its counterparts. While it may be regarded as a material associated either with luxury construction or a low-priced alternative, timber’s versatility is such that it readily steps up to a timber-only or hybrid high-end brief and could, with prefabricated engineering, respond judiciously and effectively to South Africa’s housing predicament. Never, though, should timber construction be promoted, classed or executed as a cheap alternative.

This article was first published here in the June/July 2018 issue of Timber iQ.

 

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