2.8 Spread from neighbouring buildings
Buildings are at risk from fires starting beyond their boundaries. The area of greatest vulnerability is the roof and there may be a risk of ignition or penetration by burning brands, flames or heat. The degree of protection for roof coverings is dependent upon the distance to the boundary.
A roof covering consists of one or more layer of material such as felt, tiles, slates, sandwich panels etc., but is not intended to include the whole of the roof structure. Solar roof panels should be regarded as forming part of the roof covering and as such should be able to resist ignition from an external source. Most solar panels are glazed and their ability to inhibit fire spread can be determined by the thickness of glass which makes up the panel (see table to annex 2.C).
A roof covering or roof light which forms part of an internal ceiling lining should also follow the guidance to Standard 2.5 Internal linings.
Green roofs have become popular in recent years. Best practice guidance can be found in ‘Fire Performance of Green Roofs and Walls’ published by the Department of Communities and Local Government.
Conversions - in the case of conversions, as specified in regulation 4, the building as converted shall meet the requirements of this standard in so far as is reasonably practicable, and in no case be worse than before the conversion (regulation 12, schedule 6).
The possibility of direct flame impingement from neighbouring buildings is greater where the roof covering of the building is close to the boundary. Whilst much will depend on the fire dynamics and the velocity and direction of the wind, burning brands are also likely to be more intense. For these reasons, the vulnerability of a roof covering is determined in relation to the distance of a building to the boundary.
Not more that 6m from boundary - the roof of a building, including any rooflights, but excluding any wallhead fascia, flashing or trim, boxed gutters, soffit or barge boards, should have a low vulnerability if not more than 6m from the boundary. Common materials that normally attain the criterion include, slates, tiles, glazing, sandwich panels and certain plastic materials as described the table to annex 2.C.
More than 6m but not more than 24m from boundary - the roof of a building, including any rooflights, but excluding any wallhead fascia, flashing or trim, boxed gutters, soffit or barge boards, should have a low or a medium vulnerability if more than 6m but not more than 24m from the boundary. Common materials that normally attain the criterion include felts and certain plastic materials as described in the table to annex 2.C.
More than 24m from boundary - where a building is more than 24m from the boundary, the roof may be of any material, including materials of high vulnerability classification.