What does BS 8579 tell us about the fire performance requirements of balconies and terraces?
The 31st August 2020 was an important day for the external envelope industry. It was the day that BS 8579:2020 Balconies and Terraces was published. Why is this document so important you may ask? Put simply, even though it is only guidance it is being looked at as THE document that unlocks the confusion over exactly what a balcony is, providing a clarification of exactly what type of balcony is a ‘specified attachment’ within Approved Document B Regulation 7.
If you haven’t had a chance to read this important new British Standard yet the answers are;
Projecting open balconies, projecting enclosed balconies, recessed open balconies and recessed enclosed balconies are all balconies; whether thermally broken or cantilever.
Recessed open terraces, recessed enclosed terraces and access terraces are all roofs.
Terraces are roofs, but have a slightly different requirement depending on their distance from the boundary. But require a Broof(t4) fire exit route.
Not any clearer? The simple way to remember the requirements are “if it’s over air it’s a balcony”, “if it’s over heated space it’s a roof”.
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So, if it’s classed as a roof on a relevant building to demonstrate compliance with the requirements of Approved Document B the installed roof system must be either tested to BS EN 13501-5 and classified as either Broof(t4), Croof(t3), Droof(t4), Eroof(t4) or Froof(t4) depending on the distance from the boundary, or have a surface finish as defined by Commission Decision 2000/553/ EC of 6 September 2000; loose laid gravel with a thickness of at least 50 mm or a mass ≥ 80 kg/m2 (minimum aggregate size 4 mm, maximum 32 mm),sand/cement screed to a thickness of at least 30 mm, or cast stone or mineral slabs of at least 40 mm thickness. However, in reality, most specifications are defaulting to a requirement of Broo(t4). But this still means you can use a BS EN 13501-1 Class E insulation board within the build-up, unless insurers require otherwise.
If it’s classed as a balcony (built over air) the entire build-up, apart from the waterproofing membrane, must be constructed of materials achieving fire performance class A1 or A2-s1,d0 to BS EN 13501-1, something called ‘non-combustible’. This includes the insulation board and surface finished, but the roof membrane which is exempt under Regulation 7(3)(g).