Marley highlights the importance of fire barriers

Marley highlights the importance of fire barriers

Stuart Nicholson, Roof Systems Director from Marley, explains how a new, easy-to-install fire barrier can help reduce the risk of fire spreading through roof voids.

Fire barriers are an unseen, but very important, product when installing a pitched roof on terraced or semi-detached housing. When a roof is compartmentalised, fire stopping is required between the top of the party wall and the roof covering, acting as a seal to prevent spread of flames and smoke between properties in case of fire.

However, there is some concern that some modern homes could have inadequate, incorrectly installed and, in some cases, no fire barriers at all. In terraced or semi-detached properties, this increases the risk that fire could spread rapidly through roof voids from one home to the next.

Why are fire barriers inadequate or incorrectly installed?

Fire stopping is often achieved with a flexible mineral fibre quilt or sock, but a potential fire passage still exists at the line of the roofing battens, above the rafters, which can span across the junction between properties. There are fire barrier products available on the market to close this gap, but these can be bulky and difficult to install in line with the roof tiles, especially with deep profiled tiles. It is also difficult to see if the fire protection is in the correct place once the tiles have been laid. This means there is a risk that a fire barrier is present, but it may not be installed correctly, or might not be sufficient to fully seal the gap.

How can contractors reduce their risk?

The new, easy-to-install, Marley Roof Defence fire barrier gives builders the confidence that it is correctly fitted and will provide full fire protection, from one roof to the next, achieving up to a 60-minute fire rating. It features two strips of intumescent material bonded at 90 degrees, with an inverted T design, that can simply be installed under tiles and between roof battens to close all gaps in the event of fire.

How is Roof Defence different to other fire barriers?

  • Roof Defence has an inverted T intumescent seal, which expands when activated by heat, filling the space between roofing battens and sealing all spaces under the tiles, slates, and other roofing elements. The double intumescent strip and inverted T design, make it much more effective at filling both horizontal and vertical spaces.
  • Whereas some other systems are rigid, Roof Defence is flexible, lightweight and is supplied on a roll, so it can easily be taken onto a roof and rolled out over the party wall. This also makes it easier to use on uneven surfaces.
  • Using a compressed mineral fibre option can affect the way the roof covering is fitted. This is because, to be securely fixed, the projecting nibs on the underside of tiles must have space to hook on the rear face of the roofing batten. A compressed mineral fibre quilt, or sock, occupying this space can interfere with this. It can also block important ventilation paths on large, compartmentalised roofs, causing additonal ventilation problems.

Roof Defence ensures clearance until activated by the heat of a fire, so it doesn’t affect the fit of the roof covering or block ventilation.

When it comes to fire stopping in the roof, often limited details are given in Building Regulations, so sometimes the responsibility is on builders to ensure correct detailing. Roof Defence is designed to make life easier because it removes any confusion and provides assurance that it has been fitted correctly. It has outperformed all fire testing requirements and fills every void from the party wall to the bottom tile, meaning smoke and fire cannot pass through.

For more information on Roof Defence visit

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