FR Coatings Alert

By Stephen Young, director of the Wood Protection Association

The Wood Protection Association (WPA) is calling on building designers to double-check the fire performance claims of flame retardant treatments before they commit to a specification. The move follows research for the WPA that has highlighted the potential for products, certain low viscosity coatings in particular, to be specified without the appropriate fire performance test data.

Fire safety is an important factor in building design and 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 a Notified Body (or a fire test report for BS 476 classifications) is available for the required application.

A Notified Body is an organisation that has been accredited by an EU Member State to assess whether a product meets a certain preordained standard. Fire Classification Reports state the fire performance of the treated timber after controlled testing in accordance with BSEN 13501 – 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 the classification applies. The field of application, for impregnation treatments and low viscosity coatings that are not paints, defines the minimum treatment loadings for the fire retardant, the species of timber and type of component (e.g. spruce cladding) and the allowed variation in thickness (e.g. 12mm to 25mm). For flame retardant paints standard substrates may have been used in testing that permit a wider range of substrates in actual use but this should always 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 to satisfy themselves that the description of the product given in the Classification Report quoted by the manufacturer can be taken to apply to the timber they want to use in a project.

Specifiers need to 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. Extended Application Reports provide the evidence that defines a fire retardant product’s application scope or range of substrates and thicknesses to which a Classification Report applies. If no Extended Application Report is available for the component then another treatment that is appropriate to the application should be chosen.

The WPA recognise that with more products on market than ever claiming fire performance to Euroclass standards, choosing the right product can be confusing. To help guide designers, the Association publishes a Flame Retardant Specifiers Manual which provides detailed information on the flame retardant treatment of wood and panel products. The manual includes a simple checklist setting out for impregnated, low viscosity coated and factory-incorporated products a step-by-step guide to selecting the right product for the job. The WPA also maintains a list of approved fire retardant products that meet its own product quality and performance procedures.

These procedures includes verification of independent test results and reports from Notified Bodies providing designers with an easy and highly credible source of reference and product knowledge.