Reducing Fire Risk

Due to misconceptions surrounding the use of timber and the risk of fire, there are instances where the material may be perfect for the project but wrongly avoided under a common misunderstanding. With that in mind, what needs to be considered in order to mitigate any disasters during a timber build?

Where sites are still under construction, exposed materials and methods of working may contribute to an increased risk of fire however, completed timber frame buildings, which are constructed in line with building regulations and related standards, are entirely safe and very well protected against fire.

It is this differentiation between ‘under construction’ and ‘completed’ however where the confusion lies when it comes to fire risk. Fires can be started on any construction site – sadly, all sites, regardless of the form of construction, can be targeted. The Government’s annual UK fire statistics in fact shows that two thirds of fires in construction industry premises are started deliberately.

For structural timber building systems, which are still under construction and where fire protection cladding is yet to be installed, exposed timber can provide fuel for fire to spread. It’s important to bear in mind however that all kinds of ‘in progress’ construction sites, regardless of the material used, pose this same risk, with brick and stone, concrete and steel all similarly vulnerable to the effects of fire at this early stage.

A large fire on a construction site can generate significant heat from which a fire can spread beyond the site boundary by igniting neighbouring properties or fuel sources. The STA document ‘Design Guide for Separating Distances’ provides risk mitigation against fire spread beyond the boundary by selecting the appropriate category of structural frames.

There are of course ways to help overcome this issue – in terms of robustness against fire spreads during the construction process, the STA has developed frame categories so that the choice of structural timber building system at the design phase can be determined appropriate for the site fire risk assessment. These categories are:

Category A – standard timber building system: walls, floors and flat roofs
Category B – reduced fire spread: walls, floors and flat roofs
Category C – fire spread resistant: walls, floors and flat roofs
Category CLT – walls, floors and flat roofs.

Along with this, the STA has also created its own Site Safe 16 Steps to Fire Safety document, helping to promote good practice on structural timber construction sites. The document is designed to support the on site fire risk assessment. Site Safe strategy includes all advice and documents, to provide the STA members with knowledge and information, which in turn supports the design and construction team to procure and construct fire safe buildings.

The STA advice is for commercial building projects and is relevant for construction sites with a total floor area above 600m2. The advice given is suitable for buildings below 600m2, but single house developments should be assessed on the scale of the house and location for fire risks, and the principles of this guidance should be used.

With these points in mind, it is worth employing the services of an STA member when working on any commercial or residential project where timber is at the core since members are required to adhere to the STA’s compliance guidelines on a day to day basis.

For more information on issues surrounding fire safety visit: www.structuraltimber.co.uk