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 critical for plumbers, building surveyors, builders, architects, developers and property owners.
Dam Buster products achieve compliance with the relevant NCC Performance Requirements via the two methods below (Method 1 and Method 2).
It's critically important that design and documentation of compliant roof drainage is carried out at the building permit stage so as to avoid dramas both during and after the build.
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. This method also applies only to genuine Dam Buster rainheads.
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.
NOTE: if the above approach is not acceptable to either the relevant Regulatory Authority or the Building Surveyor / Certifier, then a Dam Buster Rainhead located at the end of a straight box gutter can instead be certified under a Performance Solution using Dam Buster’s Performance Solution templates and Evidence of Suitability documentation.
Method 2 - A Combination of Solutions
‘A combination of solutions’ is used for all other genuine 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 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.
In these cases the Dam Buster device itself (excluding the rainhead) 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. If required, please Contact Us for more information.