Our industry has been overwhelmed by the sheer scale and magnitude of the recladding crisis, says Craig Fyall Technical Director at Permavent Limited, but what does not make the headlines is the building cavity and its contribution to a building’s fire rating.
We have all seen the news reports about the number of affected buildings in the UK, the cost of remedial work and the impact on all affected by it. The whole industry is consumed by the focus on cladding, without giving due consideration to what should be used as a standard in the cavity build-up.
The additional challenge of identifying and extinguishing a fire within a concealed cavity can be notoriously difficult for obvious reasons. The NHBC’s and BRE Trust’s TF2000 study attests to this, whilst also identifying the supporting role a combustible membrane can play in accelerating any fire spread. It’s critical to put the emphasis on cavity design at the planning stages of any construction project. As an industry we have a duty of care to make sure the same mistakes are not repeated, by cutting corners specifying products which contribute to fire due to their inferior performance characteristics.
Achieving a Class A rating when manufacturing a membrane is exceptionally difficult: one must consider the substantial differences in the testing methodologies and the product performance. It is important to understand that whilst a B classification is defined in BS EN13501 as having a “limited contribution to fire”, an A rated counterpart “will not contribute to a fire”. This being the case, why are class B products still being specified when they can by nature contribute to a fire on an external wall, regardless of how limited that contribution may be? This is true to the point that the NHBC now recognise advances in membrane technology and that an A rated membrane should be used wherever possible.
For more information visit: www.permavent.co.uk
Source: Offsite Magazine issue 41
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