Plastic rooflight distance from relevant boundary

Where a roof incorporates a plastic rooflight, which is not designated AA, AB, AC, BA, BB or BC (National class), or BROOF(t4) or CROOF(t4) (European class), the minimum distance from that rooflight to a relevant boundary should be not less than that given in Tables 5.8 and 5.9 for the appropriate classification of the rooflight and the space over which it is located. For the purposes of this paragraph and Tables 5.8 and 5.9 a rigid thermoplastic rooflight, made from polycarbonate or unplasticised PVC, which achieves a Class 1 classification for surface spread of flame (see paragraph 3.4) may be regarded as having an AA (National class) or BROOF(t4) (European class) designation (other than for the purposes of paragraph 4.21(a) and Diagram 4.2).