The Myths About Non-combustible Insulation in Flat Roofs

In late 2018 the Ministry of Housing, Committees & Local Government (MHCLG) made significant changes to the legal requirements within the Building Regulations 2010 in England. The Scottish Government soon followed suit. The result of the investigations into the Grenfell Tragedy and the subsequent Hackitt Review recommendations had a significant impact on what materials could be used in the construction of buildings over 18m tall in England and 11m in Scotland, but which changes did they make?

They banned combustible materials in external walls, roofs, terraces, balconies and podiums. Yes, and No. They DID ban the use of combustible materials or products in ‘external walls’ and ‘specified attachments’, subject to certain exclusions, requiring products to achieve a European reaction to fire classification of either A1 or A2-s1, d0 in accordance with BS EN 13501-1.

They DID NOT ban the use of combustible products in roofs, terraces and podiums, but they did leave balconies as a ‘grey’ area as well as the position regarding waterproofing membranes installed over 70° i.e. upstands.

When it comes to flat roofs Approved Documents B have changed little. They still require a flat roof to achieve a tested fire performance rating of BROOF(t4) to BS EN 13501-5, whether inverted or warm roof construction. BS EN 13501-5 tests a complete roofing system assembly unlike BS EN 13501-1 only tests a product.

Inverted roof construction however can sit outside of the requirements to conduct actual fire testing, if one of the three finishes listed in European Commission Directive 2000/553/EC are used. Those finishes are;

• Loose laid gravel with a thickness of at least 50 mm or a mass ≥80 kg/m2 (minimum aggregate size 4mm, maximum 32mm)

• Sand/cement screed to a thickness of at least 30mm

• Cast stone or mineral slabs of at least 40mm thickness

Other finishes such as 20mm porcelain tiles, timber or plastic composite decking, artificial grass, synthetic running tracks etc need to be tested in accordance with ENV1187 test4 to achieve a rating to BS EN 13501-5.

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