External timber framed walls

6.2.9Fire resistance

Timber walls and panels shall control and resist the spread of fire and smoke. Issues to be taken into account include:

  1. cavity barriers and fire stops
  2. services.

All building elements should have adequate fire resistance. Materials in accordance with building regulations are acceptable; other materials should be assessed in accordance with Technical Requirement R3.

For guidance on the prevention of fire during construction; refer to ‘Fire Prevention on Construction Sites’ jointly published by the Construction Federation and the Fire Protection Association (www.thefpa.co.uk), and guidance from the Structural Timber Association (www.structuraltimber.co.uk) under the ‘Site Safety Strategy’, including the ‘16 Steps to Fire Safety’ and the ‘Design Guide to Separating Distances’.

Cavity barriers and fire stops

The installation, position and materials for cavity barriers and fire stops should be in accordance with the relevant building regulations and the design.

Horizontal and vertical cavity barriers should be protected by DPCs arranged to shed moisture away from the sheathing. Horizontal cavity barriers, except under eaves, should be protected with:

  • DPC tray with a 100mm minimum upstand, or
  • a polyethylene-encased cavity barrier with a 100mm minimum upstand.


Only the services shown in the design should be installed in separating walls and:

  • service outlets should not impair the fire resistance of floors and walls
  • service mains should not pass through separating wall cavities.

Notching or drilling of structural timber members should be carried out as detailed in the design. If these details are not available, the designer should be consulted before such operations are begun.

In Scotland, services are not permitted within a timber framed separating wall.