CTI statement on the performance of wood cladding in a fire
The outcome of the UK government’s assessment last year of the use of different cladding materials in the wake of the Grenfell tragedy confirmed that timber, where necessary enhanced with flame retardant, remains fit for purpose where the upper floor level of a building where the upper floor level is less than 18m above ground (Building Regulations England). In all situations where Building Regulations stipulate a particular reaction to fire performance level for materials on the external face of a multi-storey residential building below this level, then those performance levels must be complied with.
However, Building Regulations guidance does not always stipulate a particular reaction to fire performance for cladding and/or balconies on buildings where the upper floor level is less than 18m above ground. In such circumstances, so as to provide consistency, insurance and peace of mind against unforeseen circumstances, an independent, professional fire risk assessment which takes into account the building design, use, materials and location is essential at the project design stage. Indeed, this has been a principle embodied in the CDM Regulations for some years which has very recently been reinforced by MHCLG in a circular letter to Building Control in England & Wales.
Such an assessment may demonstrate that, by means of careful design and component specification, flame retardant treatment is unnecessary in the particular circumstances. However, following recent reviews and from industry feedback on new projects, the Confederation of Timber Industries (CTI) recommend that all such timber based cladding and balcony components should be treated using a quality assured factory-applied flame retardant to Euroclass B, unless shown not to be necessary by an appropriate risk assessment process.
Timber remains an excellent material for manufacture and construction, but proper risk assessment, specification and detailing are paramount to ensuring safety whatever the build method.