The organisation released a statement after a report on the Collaborative Reporting for Safer Structures UK (CROSS-UK) online platform, expressed concerns about the behaviour of thermally modified timber in fire and flame retardant testing certification.
“Flame retardant treated wood for external use should meet the requirements of both a suitable reaction-to-fire classification report and a durability of reaction-to-fire classification report,” said the WPA.
“Specifically, the WPA recommends that FR products are applied under quality-controlled factory conditions. This is to avoid the quality issues that can arise from FR liquids being applied on site, which the WPA does not recommend.”
“There are many unknowns when treating wood cladding with liquid flame retardants by brush or spray on site, including the impact of different weather conditions,” added Matthew Powell, chair of the WPA’s Flame Retardant Committee. “This is why the WPA recommends only using cladding treated with proven flame-retardant products applied under controlled factory production processes.”
“Fire classification reports relating to factory applied flame retardants give building designers confidence about the performance of the materials they specify,” said the WPA. “Standards tests and classifications of the effects of external weathering on the performance of flame retardant treated wood have been in place for 30 years in the US (ASTM D-2898), 20 years in the Nordic region of Europe (NT FIRE 053) and for seven years in Europe (EN 16755).”
Information about the specification of flame retardants for wood is freely available on the WPA website www.thewpa.org.uk and through a webinar in conjunction with Timber Development UK.
