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The problem may be that the wording of the part of the regulations in Approved Document B ( AD B ) is ambiguous.

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/441669/BR_PDF_AD_B2_2013.pdf

"12.7 In a building with a storey 18m or more above ground level any insulation product, filler material (not including gaskets, sealants and similar) etc. used in the external wall construction should be of limited combustibility (see Appendix A). This restriction does not apply to masonry cavity wall construction which complies with Diagram 34 in Section 9."

Rainscreen cladding isn't insulation, it has a weather shielding and aesthetic function. The etc. at the end does provide some doubt as to what exactly is meant. However if you look at this BRE press release for the 2nd edition of the fire safety document referenced in 12.5

"BR 135 Fire performance of external thermal insulation for walls of multistorey buildings"

http://www.redbooklive.com/filelibrary/Articles/The_dangers_of_external_cladding_fires_in_multi-storey_buildings_~_RCI.pdf

By their understanding, cladding seems to be meant to be included in 'etc.' in 12.7

"any product used in the external wall construction (except for gaskets, sealants and similar components) in buildings with a storey 18m or more above the ground, must be of limited combustibility"

Taken that as read, that would mean that the materials would have to meet limited combustibility as in Appendix A on page 130 - i.e. European class A2-s3, d2 or better in European standard in accordance with BS EN 13501 - 1:2007 Fire classification of construction products and building elements, Part 1 - Classification using data from reaction to fire tests

Neither older Reynobond product, PE or the more fire retardant FR meet those tests, only meeting class B - s2, d0 and B - s1, d0 . Presumably that is why Arconic have now developed the Reynobond A2 that does meet it, referenced in their new 'fire solutions' document (dated Dec 2016, Jan 2017 in filename). The question is what if any advice did Arconic (then Alcoa) offer to distributors at the time of the Grenfell refurbishment? I have looked through all the documents on their old website and have found not one warning about building height

https://web.archive.org/web/20150905203951/http://www.alcoa.com/aap/europe/en/info_page/down_brochures.asp

So sadly it seems we are facing incompetence all round, with dodgy wording in the regulations, and the manufacturers being less than forthcoming about the safety risks of their products.

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