Introduced in 2019, the new guidance on the fire performance of external wall cladding systems left architects and designers in doubt over which claddings are compliant in buildings over 10m in height. The changes also brought into question the use of timber framing and battens on buildings over 10m in height — would these timber structures meet the new requirements for external spread of fire?
While James Hardie were confident that their range of non-combustible cladding systems provided the fire performance required, they decided to go the extra mile and undertake NFPA 285 testing in the USA in order to demonstrate compliance with the new regulations.
Two tests were conducted to provide clear answers for both architects and councils:
Test 1: RAB Board
The first test involved a RAB board fibre cement sheet fixed to standard timber frame. The aim of the test was to demonstrate that if a building is over 10m in height there would be no spread of flame as the RAB board acts as a protective layer.
Test 2: James Hardie cladding system build-up
The second test involved a cladding system build-up comprising standard timber framing, a standard lining, standard insulation and James Hardie Rab Board on the exterior of the frame, followed by timber cavity battens and James Hardie claddings on the exterior of the battens. This test was undertaken to prove that as long as the cavity is blocked at each level, the non-combustible James Hardie cladding system would meet spread of flame requirements even when using a combustible timber batten.
In each test the James Hardie build-up achieved a pass result with no spread of flame, demonstrating compliance with the New Zealand Building Code.
BRANZ appraisals updated
To provide further peace of mind to architects, the US test data was taken to BRANZ who have assessed James Hardie’s cladding systems and concluded that they meet requirements for external fire spread in buildings over 10m. This is reflected in updated BRANZ appraisals for James Hardie RAB Board and James Hardie Cladding Systems.
With James Hardie’s range of non-combustible cladding systems, architects can rest assured knowing they are choosing a system that not only meets NZBC requirements for spread of fire in buildings over 10m high but also has the testing and BRANZ appraisal to prove it.