This part of ISO 13785 specifies a method of test for determining the reaction to fire of materials and construction of façade claddings when exposed to heat and flames from a simulated interior compartment fire with flames emerging through a window opening and impinging directly on the façade. The information generated from this test may also be applicable to the scenario of an external fire impinging on a façade; however, the results may not be applicable for all fire exposure conditions. This method is applicable only to façades and claddings that are non-loadbearing. No attempt is made to determine the structural strength of the façade or cladding. This test is not intended to determine the fire behaviour of a given building façade. Details such as balconies, windows, window shutters, curtains, etc., are not considered in this test. This test does not include the risk of fire spread, for example through the window details of the façade system, as it only is constructed as a façade wall. There is clear evidence that an internal corner (also called a re-entrant corner) configuration produces a more intense fire exposure than a flat façade. The most commonly encountered internal re-entrant corner is with an angle of 90°. The test façade specimen therefore contains an internal corner with a re-entrant angle of 90°. The test method described is intended to evaluate the inclusion of combustible components within façades and claddings of buildings which are otherwise of non-combustible construction.