The tests described in this part of BS 476 are designed to give information about fires spreading to the roof of a building from a nearby fire outside the building itself.
The tests are not concerned with the behaviour of a roof when subjected to the effects of fire on its underside. A preliminary test is made in which a specimen section of the roof is subjected to the effects of flame in the absence of radiation.
Unless the specimen is so affected by this test that it is obvious it would not pass the principal tests, i.e. the penetration and the spread of flame tests, these are then carried out using the radiated heat apparatus.
BS 476-3:2004 describes the three stage test method incorporating burning brands, wind and supplementary radiant heat.
The tests are designed to enable measurement of:
- capacity of a representative section of a roof to resist penetration by fire when the external surface is exposed to radiation and flame
- distance of the spread of flame on the outer surface of the roof covering under certain conditions.
Roofs are graded according to the angle at which they are tested, the time for which they resist penetration by fire, and the distance of superficial spread of flame on their external surface.
BS 476-3:2004 supersedes BS 476-3:1975 which is withdrawn.