Section B2.3.1 of the NZBC requires components to satisfy the requirements of the building code, for 50, 15, or 5 years (according to their categorisation) with only Normal Maintenance.
B2/AS1 section 1.2.1 defines 'normal maintenance' as: "work that is generally recognised as being necessary to achieve durability for a given building element…."
B2/AS1 Section 2.1 states that it is the responsibility of the person specifying the building element to determine Normal Maintenance requirements which may be based on the manufacturer's recommendations
B2/AS1 section 2.1.3 gives examples of Normal Maintenance as: a. Following the Manufacturer's maintenance requirements. b. Washing down surfaces, particularly exterior building elements subject to wind-blown salt spray. c. Recoating exterior and interior protective finishes.
In general, NZ metal roofing materials exposed to rain washing can be expected to comply with NZBC B2 without manual washing, or replacement of protective finishes — but unwashed areas, which includes all wall cladding, may require maintenance.
Where access for maintenance of unwashed areas is impractical, the use of non-ferrous metal cladding may be advantageous in meeting NZBC requirements.