Understanding The Importance of Fire Classifications for Walling and Construction Membranes. Fire Safety: Approved Document B

Our walling Category Director and in-house expert on fire and safety in construction, Craig Fyall has put together some technical guidance on the importance of fire classifications for walling and construction membranes.

Safety should be the most important consideration in any building design Shortly after Dame Judith Hackitt’s 2017 independent review of building regulations and fire safety was the catalyst to a change in building standards and updated to address the issues in modern construction. This led to the government introducing several amendments to the design and construction of structures above 18 metres in Fire Safety: Approved Document B.

There have been additional amendments to the document reinforcing the importance of fire safety in construction; most recently December 2022. These amendments have extended the ban on the use of combustible materials in more building types which have strengthened the fire safety standards further. The Health and Safety Executive’s (HSE) Building Safety Regulator (BSR) will oversee enforcing compliance of this legislation.

The Building Safety Regulator will regulate all buildings over 7 stories or 18 metres high that have at least two residential dwellings or fit into a relevant building category (where a substantial number of people will need to be safely evacuated from the structure in the event of a fire).

So, what are the updates pertinent to walling and construction membranes?

Update to relevant buildings added to scope of high-rise buildings above 18m high:

The latest amendments have added hotels, hostels, and boarding houses to the list of relevant buildings which must conform to regulation 7(2), where such buildings will need to meet minimum fire classification standards. Other relevant buildings include hospitals, care homes, sheltered accommodation, joining apartments and more.

Update to Residential Purpose Groups 1 and 2 in mid-rise construction (11m-18m high):

The following applies to buildings where people sleep on the premises and includes habitation in a residential, institutional and hospitality setting. The external surfaces of external walls should comply with European Classification A2-s1, d0 or better.

Houses, mid-rise and low-rise buildings (11m or less):

The external surfaces of external walls within 1m of the relevant boundary should comply with European Classification B-s3, d2 or better.

Understanding the difference between fire testing classifications (BS EN 13501-1:2018 Fire classification of construction products and building elements-Classification using data from reaction to fire tests).

It’s important to understand the distinction between different fire classifications in the UK. Most notably in the case of walling membranes, the small but stark difference between a B rated membrane which has a very limited contribution to fire and an A rated membrane (A1 & A2) which has no contribution to fire.

Understanding test methodology and considerations:

Furthermore, it’s also important to remember that a product whether that may be quoted as achieving an A1, A2 or B fire classification must still conform the permeability requirements set out in BS 5250: 2021 Management of Moisture in Buildings. Failure to meet these permeability standards will exasperate and accelerate the common issues associated with condensation control and the building integrity and performance. You need to add about waterproofing for the lifetime of the building as well.

Implications for the built environment/construction industry.

The Building Safety Act 2022 has now provided all homeowners with more than twice the amount of time to claim compensation from sub-standard construction work, increasing from 6 to 15 years.

Furthermore, new rights to redress will also hold those responsible for contributing to the building safety crisis for costs to rectify their mistakes. Finally, manufacturers across construction will also be required to ensure all products they supply are safe for their intended use, with a national regulator for construction products regulating and enforcing this.

I will be presenting a CPD presentation on Fire Safety in Buildings – Cavities on Wednesday 29th March at 1.30pm Follow this link to register for free:

Please get in touch with our Sales and Technical team for more information, technical guidance product support and more.