The truth behind timber: part 3.


Louis Chaumont, Fire Engineer

Focused on fire safety.

In part 1 and 2 of this insight series we’ve explored the clear sustainable benefits of engineered timber buildings, but also established that its use is not yet widespread due to a lack of confidence and knowledge within the industry.

Probably the main area of concern is understanding its fire behaviour.

Because of this, so far, engineered timber (typically cross-laminated-timber: CLT) has been used mainly for low-rise residential, commercial, mixed-use buildings. However, as new technologies and awareness improves, architects and developers are beginning to propose high-rise buildings constructed with CLT.

We believe these new timber construction materials offer an unrivalled opportunity to create safe sustainable construction.

The complexity of fire safety with mass timber buildings comes from the additional fire loading present in the building compared to traditional buildings, as the elements of structure themselves are combustible.

Added to this is the fact that, due to the engineered timber’s composition and behaviour in fire, the standalone assumption of using the charring rates doesn’t allow us to achieve an adequate period of fire resistance.

As such, we need to explore alternative solutions to ensure that mass timber buildings can withstand a compartment burnout. These can include encapsulation, or an in-depth fire engineered analysis to assess the potential for delamination and self-extinguishment.

A full assessment.

The impact of mass timber elements on other aspects of a fire safety strategy also need to be assessed. This includes internal fire spread, vertical fire spread over the façade, or external fire spread to neighbouring buildings.

However, there is currently no guidance available in the UK to base the design of large mass timber buildings on and meet these objectives.

Thankfully, through performance-based design, we can ensure that the functional requirements of Building Regulations can be met.

While these materials present an additional level of complexity when it comes to fire safety, it’s a challenge we can overcome with the right level of understanding and expertise.

From working on multiple large-scale timber-led developments and participating in industry research, we’ve been able to support the development of mass timber as a structural material and its use in design… and it’s vital we champion how it’s possible to meet the UK’s Net Zero Carbon target and create buildings that are safe for their occupants.