Compliance with the National Construction Code (NCC)
Following the introduction of the new NCC Governing Provision A2.2.(4) on 1 July 2021, compliance of roof drainage designs is increasingly becoming the focus of Building Surveyors and Certifiers, and therefore also for plumbers, builders, architects, developers and property owners, amongst a range of others.
Dam Buster believes that detailed design and documentation of compliant roof drainage should always be carried out at the building permit stage since it is crucial for roof drainage to be properly coordinated with the architecture and structure. Failure to do so at this stage very commonly leads to non-compliant and unsafe roof drainage installations, since by the time the roof plumber is involved, it is often too late to carry out the required coordination with the architecture and the structure.
Dam Buster products achieve compliance with the relevant NCC Performance Requirements via the following two methods outlined below.
Method 1 - DtS (Deemed to Satisfy) by Expert Judgment
This method apples to straight box gutters discharging to Dam Buster rainheads only. No Performance Solution is required in this common case.
The box gutter is DtS and designed in accordance with Appendix I, Figure I1 of AS/NZS 3500.3.
The rainhead is pre-designed in accordance with Appendix I, Figures I2 and I3, of AS/NZS 3500.3, however, the rainhead itself is considered to be DtS by Expert Judgement because it differs in construction from Figure I2 due to the (fully tested) overflow chute.
Further Compliance Information
Please Contact Us for additional information if needed. Dam Buster’s Expert is Associate Professor Dr Robert Keller of Monash University, an internationally recognised expert in open channel flow, and in other areas of hydraulics.
Method 2 - A Combination of Solutions
‘A combination of solutions’ is used for all other Dam Buster devices. i.e. the Dam Buster Side Outlet and Dam Buster Rainhead combination, the Dam Buster Sump and Continuous Sump, and the Dam Buster Elbow.
The box gutter(s) is again DtS and designed in accordance with Appendix I, Figure I1 of AS/NZS 3500.3. The only minor variation is that the ‘upstream’ box gutter discharging to the Dam Buster Elbow is designed for the total (combined) flowrate in the upstream and downstream box gutters.
The Dam Buster device itself is a Performance Solution. A suitably qualified building professional such as a licenced Hydraulic or Civil engineer should devise a suitable Performance Solution where Dam Buster's products require certification under Method 2. Please contact us for more information.