Building exteriors have to meet requirements for fire propagation. There are a number of different approaches to testing in specific geographies. The North American codes specify NFPA 285 using the ‘intermediate scale multistory apparatus’. The prevailing UK standard is BS 8414 Parts 1 & 2, with the equivalent Australian Building Regulations standard AS5113: we do all.
NFPA 285 consists of one room over another. There is a gas burner in the lower room to simulate a fire. The test specimen of the external cladding system, containing a window opening and instrumented with thermocouples, is constructed on a frame which is placed in front of the apparatus. The test duration is for 30 minutes and at the fifth minute another burner is placed in the window opening. It is designed to simulate a room fire which has burst out of a window.
BS 8414 and AS5113 have an 8m high, L-shaped structure with a large hearth representing a window opening. The specimen is built onto the structure (part 1 uses a concrete block base wall & part 2 uses a steel frame substructure). A large ‘crib’ of wood sticks is ignited in the hearth and the test is conducted also for 30 minutes. The test results are classified according to standard BRE 135.