Acceptable roof materials and construction methods

Any roof will meet the requirement if – (a) it is jointless or has sealed joints, and is impervious to moisture (including metal, plastic, glass and bituminous products) so that moisture will not enter the roofing system; or (b) it has overlapping dry joints, is impervious or weather resisting (such as natural stone or slate, cement based products, fired clay and wood), and is backed by a material which will direct precipitation which enters the roof towards the outer face (as with underlay). Some materials can deteriorate rapidly without special care and they should only be used as the weather resisting part of a roofing system if certain conditions are met (see Part B Materials and workmanship of the Building Regulations). In determining whether a material is of a suitable nature and quality for use as the weather resisting part of a roof no account may be taken of any paint. Also, no account may be taken of any coating or rendering which does not itself provide all the weather resistance.