The correct timber fire retardant (FR) is essential to the performance of wood under flame. Earlier this year, the Wood Protection Association (WPA) opened a help-desk for architects seeking generic guidance on the fire protection of wood and wood-based panel products.
Access to the helpdesk is by referral from WPA members and has resulted in detailed discussions with architects about specific projects and fire retardant treatments. When fire protection of wood is called for by Building Regulations it is vital, for the safety of those who use the building, that the fire retardant specified delivers predictable long-term performance backed by independent verification.
The help-desk service is highlighting the reality of getting fire retardant (FR) specifications right is far from straightforward. Discussions with those responsible for fire protection for a project are characterised by specifier uncertainty and misunderstanding of technical issues. Some of this confusion is caused by the transition from British to European fire standards and some by the advent of the Construction Products Regulations and CE marking declarations of performance. It is however, evident that this situation is made worse by the perpetuation of certain myths and misperceptions about fire performance standards and fire test requirements. It is a key aim of the WPA to set the record straight on FR choices.
Debunking FRT Myths
The most frequent myth encountered is that Building Regulations National Class ‘0’ and the EN Euroclass B standards have interchangeable fire test requirements. As all members of the WPA FR sector and Benchmark FR quality schemes are aware, these standards have different technical requirements for fire tests and interpretation of results that distinguish one from the other. Any organisation that claims they are the same is wrong and one can only speculate that such statements are made for commercial self-interest.
Misunderstanding Fire Classification Reports
In terms of misunderstanding the technical issues, interpretation of Fire Classification Certificates is without question the key issue. And the principle mistake is a failure to ensure that the scope of a fire classification report relates to the specific species, profile and installation design they intend to use. Different species, sizes or installation design e.g. air gap/no air gap and type of backing material affect fire performance ratings. The WPA help-desk strongly urges specifiers to scrutinise fire certificates closely and demand extended application reports for even the smallest of details – for example a change of thickness of a cladding board from 25mm to 22 mm. There are some who say this is irrelevant but it is not. When it comes to the safety of those who will use the building there can be no compromises if the installation design differs from the manufacturers fire classification scope.
The golden rule is that if no Extended Application Report is available then another treatment must be chosen that does have the data relevant to the application. The other golden rule promoted by the WPA FR help-desk is that specifiers also scrutinise the Fire Classification Reports and Certificates for author/test house authenticity. Only Fire Classification Reports from valid Notified Bodies1 should be relied on to justify specification of fire retardant products.
Method of Application and Long-term Performance
Almost all help-desk referrals involve a discussion about the pros and cons of the different FR types (DI, HR and LR), the methods of application and the quality assurance of the application process under the WPA Benchmark scheme to ensure fitness for purpose. In addition we point out where other organisations like NHBC and National Building Specifications have discrete standards for FR performance that call up WPA guidance on FR specification which are focused on industrial impregnation to ensure long term performance.
Where there is interest in using a surface coating, WPA urges specifiers to make absolutely certain (not least for professional liability reasons) that the coating they intend to specify has a Fire Classification Report from a Notified Body directly relevant to Building Regulations requirement for their application. We also emphasise that the performance claimed depends heavily on recommended application rates and/or film thicknesses being achieved. When such products are applied by brush or spray on site, fire performance can only be assured when application is under an independent certification and accreditation scheme for installers.
