The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
Safeguard people from injury or illness, and property from damage, caused by surface water
Buildings and sitework shall be constructed in a way that protects people and other property from the adverse effect of Surface Water.
Surface water from an event that has 10% probability of occurring annually that is collected or concentrated by buildings, shall be disposed of in a way that avoids damage or nuisance to other property.
Surface water resulting from an event with a 2% probability of occurring annually shall not enter buildings.