In this second post of the thematic series on roofs exposed to an external fire, I am going to explain you the second method of test included in the technical specification CEN/TS 1187. This method combines the burning brands and the wind.
Method 2. With burning brands and wind.
The test consists on submitting to the test specimen to a heat source in combination with the application of an airflow from two fans located at the top and bottom of the specimen. The heat source will be a grid made of eight pieces of wood with dimensions of (10 x 10) mm and a length of 100 mm. The igniter shall be a line burner of 5 vertically oriented burner tubes located at the bottom of the wooden crib and fed with propane gas.
In addition, the tests will be carried out with two air velocities, 2 and 4 m/s. For each air velocity, 3 specimens of (1000 x 400) mm are required. The specimens will be installed with a slope of 30° and fixed on a standardized substrate. In this case and unlike method 1, the results with a slope of 30° are valid for roofs with any slope.
With respect to the standard substrates, two possibilities are offered. The first one will a combustible substrate without fire retardant (Wood particle board or expanded polystyrene) and the second one will be a non-combustible substrate (Fibre reinforced calcium silicate board or mineral wool). Another option allowed would be to use a non-standard substrate. In this case, the test results would only be valid for when using the specific substrate.
The test duration shall be 15 minutes or if the flame reaches the upper edge of the specimen. During the test, the extent of the damage produced on the specimen is measured.
As I explained in the first post of this thematic series, a classification standard is necessary to comply with national legislations. The standard EN 13501-5 will be applicable and offers for the test method 2, two possible classifications, Broof (t1) and Froof (t1). The classification criteria for the previous classes are shown below.
Table 1. Classification criteria for method 2. With burning brands and wind.
CEN/TS 1187. Test methods for roofs exposed to external fire.
EN 13501-5. Fire classification of construction products and building elements – Part 5: Classification using data from external fire exposure to roofs tests