Safety at All Costs

With timber frame construction expected to continue growing in popularity, it’s critical that any building made from the material is adequately protected against the spread of fire.

There’s no denying that timber is growing in popularity as a building material. According to a study by MTW Research, timber frame housebuilding was expected to see a £70 million increase in 2022, with demand rising rapidly across both residential and commercial building sectors.

It’s not hard to see why either. Timber is a highly sustainable material and can capture carbon better, unlike other materials such as steel and aluminium. Alongside this, it’s fast to build with, so the commercial benefits are significant for developers.

However, while the growth of timber construction is a good sign, safety remains vital. This is where the importance of cavity barriers comes in, and in the event of a fire, they must be able to perform as intended. There are some key factors around design, specification and installation that must be considered to ensure both buildings and the people within them are protected.

Cavity barriers prevent smoke and fire tearing through

Recent fire events in various building types have highlighted the performance of cavity barriers and how they are installed in buildings. Cavities act much like a chimney, so without a properly designed barrier, fire and smoke can quickly travel unseen through what can be an extensive network of connected spaces in a building.

National building regulations stipulate where cavity barriers should be installed, what they should be constructed of and how they should be fitted. There are some regulatory differences between the nations that make up the UK, both in terminology and specific requirements, but the principles are all the same – limit the spread of fire in a cavity

Balancing ventilation and fire safety

One of the first decisions to make is how to balance ventilation with fire safety. When building with timber frame, it is important to accommodate the requirement for cavity barriers while also ensuring timber elements remain dry and below the decay threshold (a moisture content of 20% of less). Timber frame construction needs a drained and vented external wall cavity behind all types of cladding. This provides a space where moisture vapour that travels through from the warm side of the wall to the cold side can ventilate away, without forming damaging interstitial condensation.

The external wall cavity is also a line of defence from the outside. It prevents wind-driven rain or leaks through the cladding from directly wetting the timber frame structure by letting moisture drain away freely. The key challenge therefore is to provide cavity barriers where required, while allowing the timber frame structure to drain and vent.

For those designing and building with timber, the Timber Frame Construction (5th edition) is the go-to publication to reference. The cladding chapter of the book provides detailed information on the