The Wood Protection Association (WPA) is calling on building designers to double-check performance claims of flame retardants before committing to a specification. This follows research highlighting the potential for products, certain low viscosity coatings in particular, to be specified without appropriate performance test data.
If wood is to fulfil its potential as a construction material, getting the fire retardant specification right is absolutely critical. The key is to ensure that a Fire Classification Report from an EU-accredited Notified Body (or a fire test report for BS 476 classifications) is available for the required application. This will state the fire performance of the treated timber after controlled testing in accordance with BS EN13501, for example Euroclass B, s1, d0. In this case, ‘B’ is the class achieved, ‘s’ is the smoke rating and ‘d’ is the burning droplets rating.
Classification Reports also specify a "field of application" to which they apply. For impregnation treatments and low viscosity coatings that are not paints, this defines the minimum treatment loadings for the fire retardant, the species of timber and type of component (eg spruce cladding) and the allowed variation in thickness (eg 12-25mm). For flame retardant paints, standard substrates may have been used in testing that permit a wider range in actual use, but this should be checked.
There is no such thing as a single Fire Classification Report that fits every species, commodity and end use application. That’s why the WPA urges specifiers also to ensure the product description in the Classification Report applies to the timber they want to use.
They should also be aware that different species, or cross-sectional sizes, and design factors such as air gaps, do affect fire performance ratings and may require an Extended Application Report. This provides the evidence that defines a fire retardant product’s application scope or range of substrates and thicknesses to which a Classification Report applies. If one is not available for the component, another treatment should be chosen.
The WPA recognises that, with more products on the market than ever claiming fire performance to Euroclass standards, choosing the right one can be confusing. Its Flame Retardant Specifiers Manual is designed to help designers, providing detailed information on flame retardant treatment of wood and panel products. It includes a simple checklist for impregnated, low viscosity coated and factory-incorporated products, a step-by-step guide to selecting the right product for the job. It also has a list of Approved Fire Retardant Products that meet its own product quality and performance procedures, with the latter including verification of independent test results and Notified Body reports.
