Fire safety of facades - Recent large scale tests

The fire behaviour of wooden facades in multi-storey wood-framed houses has been studied in a Nordic research project on the fire safety of wood (Brandsakra Trahus). Two different fire scenarios were assumed: a relatively small ignition source outside a sprinklered building and flashover of a compartment fire in an unsprinklered building. Fire tests of wooden facades with different materials, surface treatments and structures were performed on intermediate and large scales. In the case of an external fire, the most efficient way to stop the propagation of flames was the structural modification of the facade profile. Fire retardant treatment delayed considerably or even stopped the fire spreading. On the basis of the test results of the flashover scenario, the use of wood in the facades of unsprinklered multi-storey houses should be limited to 20 - 50% of the total facade area, depending on the location of the wood material. In sprinklered houses, however, wood can be used more extensively. Simple criteria based on heat flux levels to windows of the facade and falling pieces have been proposed for sprinklered and unsprinklered houses to estimate the fire safety of wood products in facades of multi-storey houses.