British and international building standards specify flame retardant materials for specific installations and structures. Flame retardant additives are incorporated within the materials or added as a coating to make them flame retardant; it is the formulation, quality and amount of these additives that determine which flame retardant tests the material will pass and what standards to which they will comply.
A flame retardant material is one that self-extinguishes; it does not mean that it is flame proof. Flame retardant materials are resistant to catching fire, reduce flammability, and inhibit, suppress or delay the production of flames. Flame proof materials are ones that are not liable to catch fire or be damaged by fire and are not readily ignited or burned by flames.
In 2002, to harmonise the classification of the reaction to fire for building materials, the European Commission introduced the Euro Fire Class System (Euroclass) based on EN ISO 13501-1.
Current regulations require an external wall construction over 18m to have a minimum Euroclass A2-s1,d0 fire safety rating. However, breather membranes are currently exempt from being part of an A1 or A2-s1, d0 vertical wall system; they are required by law a minimum Euroclass rating of B,s3-d0. In Scotland, this requirement applies to external wall constructions over 11m.
Following the introduction of the Building Safety Act in 2022, the latest regulations are subject to ongoing review and the construction industry should plan for further regulatory change. Best practice recommends the use of breather membranes which have a Euroclass A2-s1,d0 fire safety rating in line with the requirements for cladding and other external wall materials.