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    Timber Design


    009Excerpt from presentation delivered at the Cape Construction Expo, 31 October, at the CTICC, Cape Town, as part of the ‘Materials Zone’ workshops.


    People, in general, respond to wood as if connected to it somehow – it appeals to more than just the visual sense, also to touch and smell.

    If someone walks into a kitchen with a wooden counter top, or picks up one of my timber light fittings, the fist thing they do is run their hands over it – to feel it’s smoothness; sometimes they will even smell it. You don’t often see that happening with other materials.


    Some of you might think of, when thinking of using wood; of deforestation, or of the fact that it may burn? I am going to tell you the other side of the story.

    We all aware that our planet is basically in a mess:

    –  we are faced with the threat of unprecedented global warming, most of which is now known beyond any doubt to be manmade

    –  in terms of resources we’ve reached the point where current demand exceeds supply, so we’ve started eating into our capital

    –       worst still, the waste we produce is polluting the depleting remaining capital, further reducing the effective balance

    –  we face a potential energy crises

    This is coupled with expanding economies (albeit slowly at present), causing the need for ever increasing resource extraction, and a growing population, with a housing backlog currently of 2.1 million houses in SA.

    So the question is; how do we meet, not just the South African, but worldwide need for housing? …without further increasing carbon emissions and depleting resources.  What we have is the situation of Housing vs Climate Change.

    The solution that is being put forward is know as ‘decoupling’ – or achieving growth and prosperity without resource depletion and ever increasing carbon emissions

    So why should any of this effect what and how we build? The reason quite simply, is because the construction industry and the built environment consume:

    –       close to 50% of all resources globally

    –       50% of all CO2 emissions

    –       50% of energy consumed

    So the built environment can be considered the ‘low hanging fruit’ with regards improving our situation, as any improvements in the way we construct can have a real positive effect on our environment…and some think that timber can play a large role in the solution

    Comparing Building Materials

    Concrete, steel and masonry are all great building materials, over that there is no doubt.


    –       CO2 is one of the direct by-products of the manufacturing process of cement

    –       Steel is also energy intensive to produce

    –       Combined steel and concrete account for approx 8% of all greenhouse gas emissions

    –       Clay for bricks is extracted from the earth, ie it is of a finite quantity, and then fired in an energy intensive process

    And wood?

    –       wood is essentially grown by the energy of the sun, ie. never mind a solar panel or two on your roof, wood is a material born of solar power

    –       in terms of carbon, when a tree grows, it soaks up carbon dioxide from the air, giving off the oxygen we breathe as a by product

    –       if a tree is left to live out it’s natural lifespan, when it falls over and eventually rots, it gives back only the CO2 that it absorbed

    –       similarly, if it burns it gives back the same amount

    –       if you take wood and build with it, or convert it into furniture or products – that CO2 gets locked away – 1 cubic metre of wood stores 0.9 tonnes of CO2

    –       wood is the only major building material that is renewable

    –       and at the end of the lifespan of a building or product – we can burn the wood to use it’s stored (solar) energy, rather than burning oil, coal or gas to obtain the equivalent amount of energy

    –       wood has an extremely high strength to weight ratio

    –       so wood …is like natures gift to us!

    By using wood instead of conventional materials like concrete, steel and masonry, not only reduces the amount of CO2 emitted, at the rate of 0.9 tonnes of CO2 per cube of material used, but also locks away CO2 for the lifespan of the product,  and then if disposed of – makes its stored energy available.

    That’s not to say we try and use wood for everything, as each type of material has its advantages – concrete and masonry have, for example, high thermal mass, which is often required in a design – but in general, the more wood we can use to replace other materials, the better for the environment.

    So, with stats like 70% of the developed worlds populstion live in timber frame homes, why is the percentage of timber buildings so small in SA?

    Possible Reasons

    –       the perception of it as a cheaper & less desirable alternative, perhaps still a result of it’s humble iron clad origins and later cost–effective prefab holiday house, still persists amongst many

    –       though many have attempted, there has been little uptake in the cost effective housing sector

    –       due to inexpensive labour and plentiful clay, brick homes have been the historically preferred choice

    –       perceived concerns about timber buildings

    Some Common misconceptions

    Fire ….but won’t it burn down? Having you ever tried making a fire with a match and a log?

    –       Timber is combustible but not flammable, which means it needs a high temperature to get it burning …in the case of a fire – kindling

    –       Large dimension timber is very difficult to get burning, and when it does it chars, which protects the timber and slows down its combustion

    –       Fire engineers can calculate burn & charring rates, and hence the safety factor for varying sizes of timber

    –       The are fire retardants available, for example for timber homes in close proximity – to avoid the spreading of fire

    –       Timber keeps structural integrity for longer than steel when in a fire

    –       Timber doesn’t change dimension under high temperatures

    –       Timber’s performance in the case of a fire is very predictable

    –       Effective design for fire safety is not about preventing a building from burning if a fire gets out of control – but rather to ensure a safe evacuation of the occupants – ie the structure must remain stable long enough to get everyone out safely.

     Deforestation ….but you are cutting down all the trees, and there won’t be any left – that can’t be good!

    –       as mentioned early, we need to build and we need more housing for a growing population, and wherever we can use wood instead of high carbon emitting, and higher embodied energy non-renewable materials, we are doing the environment a favour

    –       cutting the wrong trees and transporting timber halfway around the world is not sustainable, but utilising local timber from managed plantations is perfectly sustainable

    –       wood is a renewable resource, for every tree harvested another can be planted. SAFCOL, one of SA’s large forestry companies, are currently planting more than they are harvesting

    –       SA has more than enough SA Pine to meet current housing needs, and some of our forest areas are underplanted, so if / when demand grows planting can be increased

    On renewability, the Canadian Architect, Michael Green, who is developing systems for building multi-story high rise timber buildings, has calculated that;

    to grow the equivalent of anough wood for a twenty storey building, taking into account all of the forest areas of the US, will take effectively only 13 minutes

    Durability  …how long will my home last?

    –       there are timber homes and buildings which have been standing for 100’s of years

    –       preservative treatments can prelong the lifespan of timber indefinitely. I mentioned insects with a taste for timber earlier. The reality is that wood is food for some, particularly softwoods – so it must be treated


    In trying to better understand attitudes towards timber homes, given the clear advantages and consistently small uptake, I at the end of last year, along with Timber IQ magazine, did a Timber Building Poll. We had just short of 120 respondents, of which 38% had previously or currently still, lived in a timber home. What was most interesting to me was how the responses of those who had, and hadn’t actually lived in timber homes, compared on average for the same questions.

    When asked to rate timber homes compared to brick, where an answer of 1 is much less, and a 5 far superior, in favor of timber, for the requirement of maintenance, the average scores were as follows:

    – Maintenance requirements: People having lived in timber homes                        2.87

    – Maintenance requirements: Average                                                                2.70

    So, not only was the maintenance of timber homes not seen as higher than a brick homes on average, but is was even less of a concern to people that had lived in timber homes.

    In reality though, the maintenance of a timber home can vary greatly depending on the type of timber building;

    –       a timber clad timber home will require regular re-sealing – every couple of years, though this is a relatively low skill and simple task

    –       a fibre cement clad timber frame home should require less maintenance than a plastered brick home


    I’ve discussed the advantages of using timber from an environmental point of view, but are the advantages of building a timber home; for the client, the architect or designer, and the builder?

    For the Client:

    • Insulation – and therefore energy costs. Perhaps not yet such a huge issue, but with a potential electricity hike of around 16% for the next 5 years at this stage, it soon will be
    • Natural Home – many clients chose to build a timber home because they want a more natural home, that better fits into it’s environment – something that feels good. Perhaps they feel that connection to wood. The same applies to beach resorts, and lodges in nature reserves
    • Ease of construction and time to construct – it takes significantly less time to build a timber home than a similar brick & mortar home. It’s also easier to alter or add on to at a later stage – and a lot less messy.
    • Difficult & Sensitive sites –  due to using relatively lightweight materials, timber homes are ideal for difficult to access sites – where getting timber there is pretty easy compared to bricks. For sensitive sites timber construction also allows one to nestle right in between the existing vegetation with minimum disturbance. There are also cost savings on steeps sites, by using suspended floor structures   
    • Higher floor area to building area ratio – as the walls are a lot narrow than for masonry construction, in the case of typical timber frame 150mm to around 300mm for a plastered cavity brick wall, you get an extra sq.m of floor area for every 7 RM of external wall – which can also be valuable on small sites. And should be considered when comparing square meter rates

    For the Architect / designer: 

    • Contemporary  – driven by technology everything around us is advancing in leaps and bounds. Think cellphones, tablets cars. Timber, along with other new lightweight building systems, allows us to be part of that technological revolution – rather than still building the way we were in the pre digital age. Technological advances in design software and digital fabrication technologies are now to allowing timber to be cut and fashioned to any shape you desire.
    • Versatility – So thanks to the extreme versatility of timber, your timber home could be anything from a humble log cabin, to a grand Cape Cod style beach house, a sleek glazed all round clad post & beam house, or a digitally crafted open plan contemporary house with a freeform double curved roof
    • Building Regulations – Timber homes are included in the South African National Building Regulations standards, in SANS 10082, Timber Buildings. When built to these standards they also automatically achieve the standard required for registration with the National Home Builder Registration Council (NHBRC). They are also easily designed to meet the requirements of the new Energy Efficiency regulations SANS 10400 Part XA. 

    For the Builder:

    • Passion – speak to any specialist timber builder and you are likely to find someone with a passion for their craft and for working with wood. Who would you rather have building your house?
    • Precision & neatness– building with timber is a precise form of construction. Everything needs to be just right to work. For a builder and all involved it’s easier to monitor and see that everything is working according to plan. 


    I hope I have shown you enough of the advantages of building with timber, to give it some though as an option when planning your next project.

    From our side, along with the ITFB, there is a continuous drive to increase awareness of the benefits and to promote timber frame as a building method.

    With SAFCOL, whom I consult to occasionally, there has been a drive over the last few years to change perceptions of timber buildings by building good quality timber frame school classrooms, crèches and other buildings as part of their Social Enterprise Development program. There is also currently a drive to get government departments to consider timber buildings as an option, currently with a view to timber libraries and schools – so we might see that coming on line in the next while – all of which will help promote the acceptability of timber buildings.

    From a consumers point of view I think we should few building materials the same way we view our food – instead of extracting and manufacturing – lets think about growing it!

    Nature has, after all, provided us with an option we seem to have forgotten about, a perfect building material that we can grow, harvest, re-grow and use in perpetuity.