NCCv3 & AS3500.3 Compliance for Eaves Gutter overflow
The NCCv3 (Plumbing Code of Australia) requires that where high fronted eaves gutter is fitted that it must be installed with an overflow measure that prevents storm water entering the building during a storm event with a 5 minute duration and 1% Annual Exceedance Probability [AEP].
In Victoria, there are 2 main paths to compliance with the NCCv3 (Plumbing Code of Australia) overflow requirements.
a) AS/NZS 3500.3
VBA accepted "Deemed to Satisfy" example overflow methods are set out in AS3500.3 "Appendix G" and HB:114 such as fitting gutters 25mm below the top of the fascia board or back flashing under the roof sheets to prevent backflow into the building. Please refer to the VBA website for full VBA guidance.
b) A performance solution as described in the NCC.
Should the methods (described in item a) above) under AS/NZS 3500.3 "Appendix G" and HB:114 not be suitable for your project (such as when fitting gutter to steel fascia board), a PCA Performance Solution may be implemented and MUST be planned prior to installation and implemented to ensure water will not enter the building in accordance with the PCA and AS3500.3.
Striproll Eaves Gutters fitted to Steel Fascia Board may utilise 2mm gutter spacer clips to provide overflow capacity (which is rated by a qualified independent engineer). Gutter spacers must be installed within Striproll guidelines to achieve the required overflow capacities to be used in your PCA Performance Solution and have compliance with AS3500.3. The 2mm spacer system has been rated with plain faced (un-slotted) gutter. Slots are not required to achieve the overflow capacity as tested.
You may wish to fit slotted gutter as an additional safeguard.
2mm Gutter spacers may also be utilised on timber fascias for Quad, Roundline and Feature gutter to provide the certified overflow capacity.
Please consult the local Building Authority, your registered Roof Plumber or your Roof Drainage Designer regarding full details of compliance with the legislated requirements (including PCA/NCC performance solutions) to prevent overflow entering buildings.
Contact your nearest Striproll Sales Office prior to fitting your gutters for detailed information regarding product overflow capacities.