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Durability

As the requirements of the NZBC are performance based, it is necessary to make a subjective assessment specificallyconcerning durability of the building elements covered by this Code of Practice. While it could be assumed that roofor wall cladding can be easily accessed and therefore easily replaced, the same cannot be assumed for any flashingswhich may be embedded in plaster or could not be removed without the removal of monolithic claddings. Someflashings are half hidden and as this portion would not be subject to inspection or maintenance its failure could leadto structural degradation and therefore would not comply with the NZBC. Because replacement could be classifiedas a major reconstruction, the flashing material durability requirement is 50 years. This requirement also applies tounseen flashings and secret gutters.

The NZBC does not take into account the cost or aesthetics of replacement, so while replacement period would complywith Code, it may be not considered acceptable by the client or owner. Any pre-painted cladding will change colourover time and the replacement would be visible, and the cost of replacing one long length sheet from a distantsupplier would be disproportionate to its value.

All metal roof and wall cladding and accessories should be designed and installed to comply with the durability requirementsof the NZBC, but the economic and aesthetic consequences of replacement should also be considered.

Clause: 
018_009_002_000_000_000_000_000_000
Clause Number: 
18.9.2
/cop/trash/corrosion#durability
Draft Clause: 
018_009_002_000_000_000_000_000_000