The building regulations state the regulation – set out as general principles – such as fire not being able to spread – and then the approved documents which only have the legal status of guidance. When there is any vagery or doubt about the approved documents then there is no chance of a successful prosecutions then a defending council would run rings about this. If you have any doubt about this just check out this thread from the editor of Building Design and the responses where even professional with many year of experience are unclear about the interpretation and meaning of the regs where two tables appear to be in direct contradiction.
Reynobond PE, the panel which features a polyethylene core has been tested according to the standards set out in BS EN 13501-1: Fire classification of construction products and building elements. According to the certificate the panels have a Class 0 rating for the surface spread of flame which is the highest rating.
According to Part B, the building regulation which deals with fire safety, the external envelope of a building should not provide a medium for fire spread if it is likely to be a risk to health and safety. Any insulation product or filler material used in the external wall construction of a building over 18m tall should be of limited combustibility. A table in Part B, diagram 40 shows what classification of material can be used in different parts of a building. It states that materials with a classification of class C-s3 – combustible with a limited contribution to fire – can be used in buildings up to 18m tall. A building over 18m tall must use materials with a classification of B-s3 or better. This suggests both types of Reynobond panel would meet the requirements of Part B for the flammability of external cladding.
There appears to be a contradiction in Part B. Table A7 in the appendix defines materials of limited combustibility which must be used on buildings over 18m tall. This states a material tested to BS EN 13501-1 must have a rating of A2 – s3 or better, in other words non-combustible.
A commentator summarises a presentation on fire risk of external cladding given by Dr Sarah Caldwell of BRE
on page 39, of the UK regulations for buildings above 18 metres, which clears some confusion up for us:
– External Surfaces should conform to diagram 40 – which means the rainscreen cladding must meet class 0 (national class) or Class B-s3, d2 or better (European class)
– All insulation and filler materials should be A2-s3, d2 or better (EN13501-1)
– Test the complete system to BS 8414 and classify in accordance with BR135
– All cavity barriers and fire stopping guidance needs to be followed
So Reynobond PE meets Class 0 for BS 476: Part 6 (fire propagation) and meets Class 1 for BS 476: Part 7 (surface spread of flame). It also meets the European Class B-s2, d0 (s being smoke, d droplets, lower number better). So it’s use was according to current regulations. Class 1 of Part 7 is overridden by Class 0 of Part 6, as explained by a Probyn Miers journal article last December:
There are a lot of questions. Such as why the sales literature states one standard and the BBA certificate another and why past BBA test were met but more recent BRE tests were not, but overall any defence could make a strong argument that there was reasonable doubt over whether Reynobond PE met the building regs,
There are lesssons to be learned – in particular simplifying the regulations. But simply ‘banning’ material x or y is not a satisfactory approach. A material meeting one fire test standard may be combustible when part of a poorly designed system. The way ahead is to take w whole building approach with desktop studies involving independent fire safety engineer as as part of the design process and routine large scale testing on external panel mock ups.