Bauder waterproofing systems and fire performance

On the 30th August 2019 the new edition of 'Fire Safety-Approved Document B' (ADB) came into force and with it there are a number of changes that affect flat roofing. Gone is reference to the National Classification system set out in BS 476-3:2004 as the principle determinant of external fire performance for roofs (with exception of a listing in Appendix B Table B2 that sets out the old classification system for historic projects).

This means that the European Classification system set out in BS EN 13501-5, that has run alongside the National classification system for many years, is now the main reference for external fire performance of roofs in the UK. This classification still covers external fire penetration and spread of flame of roof systems in their response to fire from outside the building, not to be confused with individual comprising components tested for reaction to fire. The test is not concerned with the behaviour of roofs when subjected to the effects of fire from the underside, ie from within the building.

New requirement of Approved Document B - 'Specified Attachment'

In late 2018 Approved Document B was amended to incorporate in B4 Regulation 7 the Government requirement to ban combustible materials as part of the external wall in buildings containing dwellings or institutions. This includes student accommodation, care homes, sheltered housing, hospitals and school dormitories in buildings where there is a storey at least 18m above ground level. It also introduced a new term 'Specified Attachment' which was included in the ban of combustible materials like the parts of an external wall. The definition includes a balcony 'attached' to an external wall. Notable exclusions are membranes (if Reaction to Fire Class ‘A’ or ‘B’) and any part of a roof (except habited mansards with a slope greater than 70°). Although, what happens if the typical flat roof waterproofing membrane is Class ‘E’ and what if you dress the waterproofing 150mm up the wall?

This new term has caused much misunderstanding with what is the definition of a balcony and it contradicts the European Commission Directive 2000/553/EC and Regulation 7(3) if a balcony is deemed to include an insulated roof. The flat roofing industry believes that attached balconies are differentiated from roof terraces in that they are not over habited conditioned spaces and are usually bolted to or cantilevering from the external wall, however this opinion, and the previous two questions, requires clarification by the Ministry for Housing, Communities and Local Government (MHCLG).
 

Bauder waterproofing systems

Bauder exposed membrane waterproofing systems achieve the highest classification for external fire testing in compliance with Approved Document B and are classed as 'unrestricted'  or 'low vulnerability' due to the fire retardant in the top layer and the mineral chippings on the reinforced bitumen membrane’s surface.

Bauder ballasted membrane waterproofing systems generally achieve compliance with Approved Document B due to the European Commission classification without further testing rules or the DCLG fire guidance on Green Roofs.

Bauder has a continuous fire testing programme where all the most common Bauder system build-ups have been tested including thick and thin insulation which means that all thicknesses in between are covered in the same approval to give the most complete cover for certification. Having only one test thickness of insulation is only valid for that thickness and no other because variance in thicknesses can change the test result, just as using generic insulation types is not acceptable as there can be differences due to the core or facings - ‘as built’ should match ‘as tested’. Our BBA certification for fire testing was up to date at publication but results can be extended by our continuous testing.
 

In summary

  • Bauder waterproofing systems are tested to   TS 1187 Test 4.
  • Introduction of the term 'Specified  Attachment' has created the question 'what is a balcony?'
  • Bauder exposed membrane waterproofing  systems achieve the highest classification for external fire testing in compliance with  Approved Document B 2019 and are classed as 'unrestricted' or 'low vulnerability.'
  • Bauder ballasted membrane waterproofing systems generally achieve compliance with  Approved Document B without testing.
  • ‘As built’ should match ‘as tested’. 

More information about fire standards and building regulations for flat roofs ►