Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture·Page 34·6.20
Cladding systems for external walls - general requirements
Cladding systems must resist precipitation penetration to the inside of the building and must not be damaged by precipitation or carry it to parts of the building that would be harmed.
Cladding systems for walls should –
(a) resist the penetration of precipitation to the inside of the building; and
(b) not be damaged by precipitation and not carry precipitation to any part of the building which would be damaged by it.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet C - Site Preparation and Resistance to Contaminants and Moisture.pdf