HOT TOPIC: Is the industry guidance for exposed mass timber sufficient?

By Ben Green, Associate Director, chapmanbdsp.

We are seeing a step-change in how exposed mass timber is being designed and assessed on schemes.

Typically, for principles embodied within standard guidance to be adopted, designers should be able to demonstrate that all parts of their building system are suitably protected, ensuring that temperatures upon the surfaces of any mass timber elements do not exceed 200°C for the minimum period of fire resistance stated within Table B4 of Approved Document B.

Put, simply, this results in the encapsulation of mass timber construction, with plasterboard for example.

Typically, to gain the full embodied carbon and aesthetic benefits that mass timber construction can offer, the desire is for such products to be exposed.

However, it must be made clear that, where exposed timber is adopted, standard guidance may no longer stack-up, and that associated design should be founded upon product specific data which is based on the dynamic response of fire within a compartment - as well as state of the art research and developments within this specialism.

For instance, reliance on basic charring rate consideration alone for large mass timber schemes is not considered appropriate for higher ‘Consequence Class’ buildings.

While the current (and under review) Eurocode 5 presents generic guidance, the conditions in a mass timber compartment are likely to differ greatly from those upon which this code is based.

At chapmanbdsp, we have the expertise and experience to meet these challenges. We know how to navigate this developing pathway and how to meet our legal obligations - to ensure that individuals in-and-around buildings, brigade and civilians alike, remain safe from, and in the event of, a fire - while also allowing schemes to meet their aesthetic and embodied carbon aspirations.

For more information contact Ben (pictured right).