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New clearance requirements to timber cladding and finished ground level

June 02, 2019

NCC 2019 Volume Two Part 3.5.4.7 now has deemed-to-satisfy requirements for timber and composite sheet cladding to be provided with a minimum clearance between the cladding and finished ground level.

This is to minimise the effects of moisture damage to the bottom of the timber or composite sheet cladding.

The clearances specified in the BCA clause are:

  • 100 mm in low rainfall intensity areas or sandy, well-drained areas; or
  • 50 mm above impermeable (paved or concreted) areas that slope away from the building in accordance with 3.1.3.3(a); or
  • 150 mm in any other case.

As well as the above requirements the wall cladding must extend a minimum of 50mm below the bearer or lowest part of a suspended floor. Consideration of other issues like termite management and bushfire requirements also need to be taken into account.

What if the manufacturer’s specifications are different to the D-T-S requirements?

The ground clearance requirements for wall cladding are based on commonly used external wall cladding ground clearance specifications published by manufacturers.

However, where a manufacturers’ wall cladding specification specifies a ground clearance less than required under the BCA, the manufacturer would need to provide documentation in the form of a product technical statement, to indicate that the reduced distance would satisfy the performance requirement P.2.2 - Weather proofing.

This would have to be provided to the relevant building surveyor/building certifier as a performance solution.

For more information, contact a HIA workplace adviser on 1300 650 620.