Fire safety assessment of wooden facades

The fire behaviour of wooden facades in multi-storey houses has been studied in a Nordic research project on the fire safety of timber framed buildings. Two different fire scenarios were considered: a relatively small ignition source outside the building and a post-flashover compartment fire. The scenarios correspond to potential fire situations in sprinklered and unsprinklered houses, respectively. Fire tests of wooden facades with different cladding materials, surface treatments and structures were performed on intermediate and large scales. In the case of an external fire, the most efficient way to prevent the propagation of flames to the upper storeys of the facade is the structural modification of the facade profile, i.e. cantilevers and oriels. Particular care should be taken so that the protrusion is of sufficient depth and width and that its front and lower surfaces are non-combustible. Using fire retardant treatment, the flame spread can be considerably delayed or even halted. Acceptance criteria for the facades of sprinklered and unsprinklered multi-storey buildings are suggested based on the test series. Similar principles can be applied when defining criteria for various test arrangements and fire scenarios.