Regulation 7 paragraph 2 of The Building Regulations states;
… building work shall be carried out so that materials which become part of an external wall, or specified attachment, of a relevant building are of European Classification A2-s1, d0 or A1 (classified in accordance with the reaction to fire classification).
Whilst there are some exclusions to this, Approved Document B specifies that;
…membranes used as part of the external wall construction above ground level should achieve a minimum of class B-s3, d0.
At OBEX, we go the extra mile. In addition to ‘system testing’, we test all our façade membranes ‘in isolation’ to determine their fire classification, ensuring a compliant BSR Gateway 2 submission.
The reason for this is simple. A system test alone can include combustible components, yet still achieve a compliant fire classification result.
However, for the fire classification of a system-tested membrane to be valid, it must be installed exactly as it was tested—using the same products and bonded to the same substrate. Any deviation from this would invalidate the fire classification test.
An example of this that’s not often given consideration is when a membrane is applied to seal the gaps around windows. One edge of the membrane is bonded to the window frame and the other edge to the substrate, but the section in between is not bonded to anything.
Testing a membrane in isolation, or free hanging, is a more stringent test than when bonded to a substrate. It allows oxygen to access both sides of the membrane, replicating a worst-case scenario.
Achieving full and genuine regulatory compliance requires thorough testing. While system testing has its place, a compliant BSR Gateway 2 submission requires manufacturers to carry out more comprehensive product testing to ensure a valid fire classification.
OBEX – Known for Quality, Trusted for Integrity