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Article: Is timber construction really all that bad?

Following the Grenfell Tower fire of 2017, there has been an understandable and widespread anxiety around construction methods. While this nervousness has rightly focused on modern methods of construction, particularly cladding, it has also led to debate around what is one of the most feared construction materials when it comes to fire safety - timber.

The use of timber in building projects is on the way up and so a big question now facing insurers is, what does this mean from a fire safety perspective? However, before looking at that, it’s probably worth understanding why there is currently a strong push for using more timber in UK construction.

In 2017, the UK Government reached an agreement with the construction industry that it would halve its greenhouse gas (GHG) emissions by 2025. Subsequent research by the BioComposites Centre for the Committee on Climate Change highlighted how increasing the quantity of wood used in construction could contribute significantly to the achievement of the emissions target.

For example, at an individual building level, the reduction in embodied emissions for substituting timber frame for masonry is around 20%, increasing to up to 60% for CLT (cross laminated timber) and concrete structures.

Tainted viewpoint?

So, there are big environmental gains to be made through timber construction, but what about the fire safety related negatives. Let’s not forget our history and the Great Fire of London of 1666, which the following year led to a ban on the use of timber framed houses in the City of London substituted by masonry. But haven't things moved on a little in the last 350 years? Is our impression of timber construction in risk engineering and insurance a little tainted by the past?

There is a case for attitudes to timber and fire safety risk being a little out of date, particularly when you explore more closely the work of the Structural Timber Association (STA), which has set high standards and issued research based technical guidelines around compliance with regulations, fire-stopping, cavity barriers and going way beyond mandatory resilience requirements. In other words, it is perhaps now a little simplistic to dismiss wood as just a dangerous flammable material.

It seems it’s less to do with what it is and more about how you use it and what other measures can be taken to make it much safer.

Architectural view

This argument is backed up by the opinion of a number of architects. Responding to a high-profile fire in south London last year involving a timber-framed housing development, Ash Sakula Architects founding partner Robert Sakula told Building Design magazine: “It’s not that there is anything actually wrong with timber frame if it’s done properly. Fire shouldn’t be able to get into the cavity.”

Writing in the Architects Journal earlier this year, Maribel Mantecon, an associate at CZWG Architects, said: “Not all timber products have the same level of fire-resistance. Mass or engineered timber can match or exceed the performance of concrete and steel.

“In the UK, structural elements over 18m require two hours of fire protection. Under test conditions, 180mm cross-laminated timber lasts over three hours. Performance-based fire engineering needs to be taken into consideration to meet building regulations.”

In addition, a recent blog post from engineers Elliot Wood, highlighted ’10 things we’ve learned about timber construction and fire safety’. Among the issues highlighted in the piece are build quality - where specifications are simply not met, calling for a stricter inspection regime - and the importance of additional fire-proofing measures, such as sprinkler systems.

Don’t demonise?

Clearly, we need to be cautious about taking an overly-simplified view of timber construction. It would certainly be unwise for risk engineers and the insurance industry in general to counter any positive environmental aspects by adopting a blanketed position of negativity.

Of course, we must recognise that timber is flammable, but should we be demonising it? Perhaps there is a need to familiarise ourselves more closely with the technical elements, such as the guidance from the STA and to play more of contributory role through our surveying and also issuing strong demands for better controls, such as though mandatory sprinkler systems.

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