10 things we've learnt about timber construction and fire safety

Everyone knows that wood can be a highly sustainable construction material. It is naturally durable, renewable and has a low carbon footprint. There is also evidence to suggest that some mass timber products can match steel and concrete in terms of fire resistance. Despite this, many local authorities and housing associations are vetoing the use of any timber in new residential projects. In the aftermath of the Grenfell Tower disaster and others, they are under pressure to make fire safety their number one priority. Whether or not timber contributed to these fires doesn’t matter – as far as the public are concerned, this material is high risk. Timber needs an image change, or people won’t want to see it in their homes.

Cross-laminated timber, or CLT is one of the strongest timber products on the market. It wasn’t possible to build a timber-framed high-rise before it came along. The problem it faces is that, unlike steel or concrete, it will burn. That doesn’t necessarily mean it is more likely to collapse in a fire, but it does mean that it fails to comply with UK building regulations. “That's not the fault of CLT, it's the fault of building regulations put together over 70 years ago,” says Ian Slater of B&K Structures, a specialist in timber construction. The only way around regulations at present is to protect the timber, to encase it in fire protection, which immediately reduces the overall sustainability benefits. But that could change if verified safety testing measures were introduced. “We know you can design safe, tall CLT buildings because of extensive testing that’s been done in America” adds Slater. “We just need to prove it in the UK.”

It’s possible for a building to be fire safe on the drawing board but not in reality. If fire prevention measures are not correctly installed, then any structure – wood or not – can become hazardous. Architect Jonathan Manser, CEO of The Manser Practice, has seen several examples of this. “The building industry in this country is shockingly bad,” he claims. “I am involved in one project taking cladding off a building and discovered that all the fire barriers were missing.” Build quality is essential to ensuring the durability of any structure, timber or otherwise. Demanding a proper, independent inspection system may be the only solution.

All buildings require maintenance, even if they are built from heavy-duty materials like stone and concrete, so any architect or contractor that promises their client a maintenance-free building is lying. And while timber if often thought to be hard to maintain, it really only needs to be kept dry in order to have an indefinite lifespan. There are wooden structures all over the world that prove it, from seventh-century temples in Japan to tenth-century stave churches in Norway. Kathy Gibbs, an engineer with KLH Sustainability, suggests that more buildings should come with Operation and Maintenance Manuals, to ensure they are better looked after. “There needs to be a good O&M Manual for everything you produce,” she says.

It became clear, after the Grenfell Tower fire, that many countries see the UK as an authority on construction regulation. The knee-jerk reaction against combustible materials from the UK building industry was reflected across the Commonwealth and in the Middle East. “They thought they were okay because we'd done the homework,” says Chris Paul, a partner at law firm Trowers & Hamlins. Paul, who specialises in construction law, explains that the Middle East in particular often follows UK code, even though the climate there is completely different. So if the UK was to introduce new regulations promoting timber buildings, more might also start to appear elsewhere.

Many of the challenges involved in timber construction can be overcome through the use of off-site construction. If you prefabricate a structure in a factory, it is much easier to ensure that is assembled correctly and makes efficient use of materials. Sweden, a country with a long tradition of timber construction, relies on prefabrication to ensure its high standards of construction. “There's more precision, less gaps, less surprises on site,” explains Lukas Thiel, an architect at Scandinavian firm White Arkitekter. “It's a more controlled environment.”

There is no doubt that CLT offers a lot of potential, but there are plenty of times when other wood products are better suited, both in terms of sustainability and material efficiency. One alternative is glued laminated timber, or glulam, which is also in the family of engineered woods known as mass timber, but requires less material to produce. However on low-rise structures, where fire safety is a far less complex issue, solid wood frames are often the best option. “If we as an industry are going to try and maximise the amount of timber that we're using, we need to treat it like a precious resource,” suggests Mark Skelly of Skelly & Couch. “Too often there's a tendency to add layers of construction, rather than keeping it simple.”

The concept of the circular economy – that all products should be as reusable as possible and the concept of waste eradicated – looks set to disrupt the construction industry. A recent report by the Mayor of London’s office is already calling for architects and developers to put circular principles into practice. This means designing buildings to be adaptable, using materials that can be easily recycled if the structure ever needs to be dismantled. “As a developer, my responsibility is to make sure the way that buildings are put together means that you can get to those materials,” says John Nordon, Creative Director for Igloo Regeneration. “We're really setting the ground rules for people that follow us.” There is a big opportunity here for timber, a renewable material with low embodied energy, to play a part in this.

There are times when timber isn’t the most sustainable material choice for a building. There are a lot of factors to consider and things are not always as straightforward as they seem. “It depends on the building typology and it depends on where the building is in relation to source of materials,” notes Kathy Gibbs of KLH Sustainability. While timber in itself is a great carbon sink, the source of the wood, the fixings and the resin (in the case of CLT) can all play a big part. It is not always obvious.

Ultimately, the most effective way to ensure fire safety in a timber-framed building is to install sprinklers. There have never been multiple fatalities in a fully sprinklered building in the UK, apart from in the event of an explosion, while the total number of deaths from fire worldwide in sprinklered buildings is just a fraction compared to unprotected buildings. No other fire safety system can match this. So, if you want to give peace of mind to residents using timber buildings, then sprinklers are the answer.