A RECENT fire in Barking, that engulfed 20 flats with wooden balconies, has put timber under the spotlight with questions being raised on how to minimise the risk of fire during the construction process.
Here, Jeremy English, UK Sales Director of Södra Wood, offers some advice.
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.
Why is timber use growing in popularity?
Durable and versatile
Timber 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.
Low carbon footprint
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.
Predictable charring rates
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.
Evidence shows 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.
Mitigating fire risks during construction
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.