Part B "Fire Safety"
All timber framed buildings rely on applied finishes to provide fire resistance to the structure. Prestoplan has fire test evidence to support specifications providing 30, 60 & 90 minutes fire resistance.
One of the questions frequently raised is how to deal with Approved Document B1 clause 6.19. This clause states;
"6.19 The flights and landings of every escape stair should be constructed of materials of limited combustibility in the following situations;
- if it is the only stair serving the building, or part of the building, unless the building is of two or three storeys and is in Purpose Group 1(a) or Group 3;
- if it is within a basement storey ( this does not apply to a private stair in a maisonette );
- if it serves any storey having a floor level more than 18m above the ground or access level
- if it is external, except in the case of a stair that connects the ground floor or paving level with a floor or flat roof not more than 6m above or below ground level.
- If it is a firefighting stair ( See Section 18 )"
As part of the TF2000 project at BRE Cardington a full scale fire test was carried out to prove that the use of vac-vac fire retardant treated softwood stairs would fulfil the functional requirements of the Regulations. Those requirements are:
- The timber stairs should not add to the fire load ( i.e. provide fuel for the fire )
- The stairs should inhibit surface spread of flame.
- After the fire the structural integrity of the stairs should be intact and sufficient to allow evacuation.
The fire test passed all these criteria and as a result it is now common practice in England and Wales for the approving authority to grant a relaxation to permit the use of fire rated timber stairs.
See Fire Retarded Timber Stair Specification treatment details. Download TF2000 Stair Report
