2.7 Spread on external walls
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Standard 2.7 Every building must be designed and constructed in such a way, having regard to the height, use and position of the building, that in the event of an outbreak of fire within the building, or from an external source, the spread of fire on the external walls of the building is inhibited. |
There is a risk of fire spread on the external walls of a building. Fire could break out through a window or door opening and spread onto the external walls. External walls close to the boundary are also at risk as they may be exposed to direct flame impingement or radiant heat flux from a fire in an adjoining building or other external source.
The use of highly combustible metal composite material panels referred to and defined in Regulation 8 of the Building (Scotland) Amendment Regulations 2022 is prohibited.
Vertical and horizontal fire spread between dwellings should be inhibited by the construction of separating walls and floors and the provision of fire barriers and cavity barriers. See guidance to Standards 2.4 and 2.7.
Fire-fighters may not be able to apply a water jet from a fire-fighting hose directly onto a fire that has spread onto or within an external wall high above the ground. This is because the external wall is either inaccessible or is out with the reach capability of fire-fighting equipment. Therefore, the construction of external walls in taller buildings should not contribute to the development of fire or contribute to vertical fire spread up the facade of the building. The 11m storey height in clause 2.7.1 and clause 2.7.2 is based on the reach capability of a fire and rescue service ground mounted water jet where there is sufficient pressure and flow in the water main. Designers are encouraged to seek early advice from the fire and rescue service if they wish to vary from the guidance where, for example, the facade is accessible to high reach appliances. Also, see Regulation 8 and annex 2.B for exceptions.
The guidance for fire spread on external walls should not be assessed in isolation and reference should be made to the guidance to Standard 2.4 for fire spread in cavities and the guidance to Standard 2.6 for fire spread to neighbouring buildings.
The Building Standards Futures Board has been established to improve the performance, expertise, resilience and sustainability of the Scottish building standards system. A key work stream currently under development is the creation of a Compliance Plan to ensure that designs, receiving a building warrant, are constructed in accordance with the building regulations and approved drawings. External wall cladding systems and specified attachments are considered safety critical features. In the interim, documented evidence of proof of compliance should be submitted to the local authority verifier which demonstrates that the system as approved has been constructed in accordance with the building warrant.
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).
2.7.1 External wall cladding systems
External wall cladding systems attached to a domestic building or sheltered housing complex having any storey at a height of more than 11m above the ground, must be constructed of products which achieve European Classification A1 or A2, subject to some limited exceptions (see Regulation 8 and annex 2.B).
External wall cladding systems - means non load-bearing components attached to the buildings structure, for example, composite panels, clay or concrete tiles, slates, pre-cast concrete panels, stone panels, masonry, profiled metal sheeting including sandwich panels, rendered external thermally insulated cladding systems, glazing systems, panels, weather boarding and ventilated cladding systems. For the purposes of compliance with the building regulations and associated standards, external wall cladding systems also include spandrel panels and infill panels. Many systems incorporate support rails, fixings, thermal insulation, fire barriers and cavity barriers located behind the outer cladding.
Sheathing or backing board - attached to and providing structural support to the frame is not considered to form part of the external wall cladding system. However, where combustible sheathing or backing board is proposed in any building with a storey 11m or more above the ground, a large scale facade fire test should be carried out (see annex 2.B).
Service penetrations - service penetrations such as flues, pipes, ducts or cables are not considered to be components forming part of an external wall cladding system.
All situations – the use of highly combustible metal composite material panels referred to and defined in Regulation 8 of the Building (Scotland) Amendment Regulations 2022 is prohibited.
External wall cladding more than 1m - from a boundary may be constructed from combustible products which achieve European Classifications B, C, D or E. This guidance does not apply to domestic buildings having a storey at a height of 11m or more above the ground (see Regulation 8 and annex 2.B).
External wall cladding not more than 1m from a boundary - should achieve European Classification A1 or A2 except cladding to a house where:
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the cladding achieves a European Classification B
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the wall behind the cladding has the appropriate fire resistance duration from both sides, and
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the topmost storey is less than 11m above the ground.
Storey height more than 11m – Where the building has a storey at a height of more than 11m above the ground the external wall cladding system should be constructed of products achieving European Classification A1 or A2.
There is a risk of vertical fire spread from specified attachments to an external wall including balconies, solar panels and solar shading. Fire-fighters may not be able to apply a water jet from a fire-fighting hose directly onto a fire that has spread onto specified attachments high above the ground.
Where a relevant building has a storey at a height of 11m or more above the ground, specified attachments must be constructed of products achieving European Classification A1 or A2.
Where a building (other than a relevant building) has a storey at a height of 11m or more above the ground, specified attachments should also be constructed of products achieving European Classification A1 or A2.
Extendable and retractable solar shading products such as awnings and canopies are not considered to be fixed solar shading attachments within the context of Regulation 8.
However, awnings and canopies should still be considered on a risk based approach to assess the potential for vertical fire spread in accordance with Standard 2.7. For example, multiple canopies vertically aligned on every storey of a building having a storey at a height of 11m or more above the ground possess a much greater risk of vertical fire spread compared with an awning or canopy located on the ground or basement storey only.
Signage is not considered to form part of an external wall cladding system or specified attachment.