“Timber is becoming increasingly popular as a construction material and not just for external structures like the balconies highlighted at Barking. As with any building material, it’s all about understanding what you are working with.
Timber frame construction now accounts for around a quarter of all new homes being built in the UK, with all sectors in the construction industry using it, including social housing. Let’s start by looking at the growing popularity of this build method.
What’s driving the move away from bricks and mortar? And why do so many architects now choose to specify timber.
There are a number of reasons for increased demand for timber as a building material. Firstly, it is remarkably strong and durable – so even with fast construction methods, there’s no risk of compromising on quality.
It’s also extremely versatile, offering the design flexibility you may need as an architect to achieve your aesthetic vision or meet specific planning requirements.
For example, a timber frame can be clad in a wide range of external materials to comply with local regulations.
In addition, timber has excellent environmental credentials. It’s a natural, sustainable material and, during its lifetime as a tree, will sequester significant amounts of harmful carbon dioxide.
Once harvested, it’s also relatively lightweight, making it cheaper and easier to transport. Its carbon footprint is therefore much lower than for other build methods.
Indeed, recent climate-change studies have shown that timber construction reduces greenhouse gases by about 50% compared to concrete structures.
Timber offers other key benefits too. It’s aesthetically pleasing, creating a more attractive end-product than with many traditional construction methods.
And it enables quicker, quieter, and less disruptive construction, making it ideal for brownfield site construction, urban development and building above underground structures, such as Crossrail 2.
Given these considerable attractions, it’s little wonder that timber is increasingly in demand and it’s likely this trend will continue. But if, like many others, you’re considering specifying timber in a construction project, should you be concerned in the light of last year’s Barking fire?
My advice is to take a considered approach and look at the evidence. Timber does not, in itself, carry greater fire risks than any other building material.
Most things will burn when you subject them to sufficient energy and oxygen, and many factors affect building fires including design and how the system is engineered and constructed.
What the evidence shows is that timber products have very predictable charring rates. When you expose a beam or truss to fire, the load-bearing core will remain intact within an outer char layer.
The char layer will act like insulation, preventing an excessive rise in temperature within the unburnt core. This means that the core will continue to function, providing a predictable period of fire resistance that allows time for a building to be safely evacuated and fire services to arrive.
By specifying an appropriate cross-section and number of timber-ply layers, you can therefore ensure that a structural timber member is sufficiently sized to retain its structural integrity for defined periods in a fire.
The one time when a timber frame building is vulnerable is during the construction phase. But here too you can mitigate the risks. For example, you can take the construction off-site by specifying closed-panel solutions.
Made from studs, rails and insulation, with sheathings and/or linings on the faces of the panel, these offer excellent thermal and airtight properties.
Alternatively, you can specify that timber products should be treated with a flame-retardant shield. At Södra, for example, we can supply timber treated with Protim Frameguard®.
This is a combined flame retardant and preservative treatment that will reduce flame spread in framing timbers and plywoods during construction.
The Structural Timber Association already has considerable fire-resistance testing data and is currently looking at how structural timber systems can best be exploited in modern, high-performance buildings. I look forward to reading their findings in due course.
In the meantime, if you want to specify timber frame construction, then make sure you are fully compliant with building regulations and relevant legislation such as CDM 2015 and HSG 168. And if you do have any concerns about the timber you’re using, seek advice from your timber supplier.”
Address: Södra Wood Ltd, Unit 18/19, Cirencester Office Park, Tetbury Road, Cirencester GL7 6JJ
Phone: +44 (0)1285 646000
Fax: +44 (0)1285 646020
Email: [email protected]
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