Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture·Page 34·6.22
Cladding materials and construction methods for weather resistance
Cladding meets weather resistance requirements if it is jointless or sealed and impervious to moisture, or if it has overlapping dry joints and is backed by material directing water outward.
Any cladding will meet the requirement to resist the weather if –
(a) it is jointless or has sealed joints, and is impervious to moisture so that moisture will not enter the cladding (such as metal, plastic, glass and bituminous products); or
(b) it has overlapping dry joints, is impervious or weather resisting (including natural stone or slate, cement based products, fired clay and wood), and is backed by a material which will direct precipitation which enters the cladding towards the outer face.
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