Communique June 2017
On 1 January 2017, a restriction on the use of combustible external cladding was published as part of Amendment 4 of Acceptable Solutions NZBC - C/AS2–7. The changes have introduced some problematic issues and, a matter of risk management, you should consider whether there is the potential for work in progress to require re-work because it may not meet the new amendments. It is known that some firms have had to put work on hold until MBIE clarifies the such concerns, some of which are noted below.Previously, buildings up to 25m high or those with sprinkler protection required no testing of external cladding material. This latest amendment removes this clause so all cladding for buildings over 7m high requires a fire test. The test is small-scale cone calorimeter test to ISO 5660 that rates the total and peak heat release rate of the material. The higher the heat release rate the more combustible the material.The building height is defined as the vertical distance between floor level of the lowest occupied space to the highest roof level. If any part of the building exceeds 7m, then so-called combustible cladding cannot be used anywhere on the building.This amendment was in response to several high-profile fires in Melbourne and Dubai which highlighted the risk of combustible external cladding material on high-rise buildings. Although these buildings were all fully sprinkler protected, fires that started on the outside of the building were responsible for rapid fire spread over several storeys.Historically, New Zealand requirements have been developed on the theory that fires generally start inside buildings where sprinklers can control and prevent them spreading. However, based on the fires in Melbourne and Dubai and most dramatically illustrated with the recent Grenfell Tower tragedy, fires can start on the outside of buildings and create significant damage and even death, which has brought this issue into the public consciousness.For architects, cladding means all exterior weather-resistant components including battens, RAB board, underlays, all cavity components, windows, doors and all penetrations, flashings, seals, joints and junctions. The testing requirement applies to all components within the cladding system.Currently, the non-combustible materials that meet the new requirements without testing are concrete, brick/block, ceramic tile, aluminium, glass, steel, cellulose fibre-cement products with applied finishes/coatings less than 1mm thick.More importantly, it appears some of the most commonly used cladding used on buildings over 7 metres including all timber and plywood cladding, TRESPA-type panels, Aluminium Composite Panels (ACP), timber cavity battens, some RAB boards and some building papers are now considered combustible and would fail the new requirement.In short, unless cladding to your 7m+ building passes the small-scale cone calorimeter test to ISO 5660, it is not permitted. This includes all components within the cladding system. At a stroke, this has excluded many common building practices/ materials on the NZ market.We await MBIE’s response.