High front guttering advisory committee report - NSW Fair Trading ...

management may assist in mitigating the chances of such overflow. Alternatively, there is the
prospect that many houses have yet to be exposed to a 100 year ARI. More detailed conclusions
follow:
Overflow
Conclusion: Overflow measures are important to the performance of high fronted guttering and
should be seen as a responsive measure contained in Deemed to Satisfy solutions (and other
Building Solutions) that meet the BCA performance requirements (e.g. no water entry to the building
given a 100 year ARI). Current Deemed to Satisfy solutions do not currently deal with overflow
adequately or objectively or in a way that is suited to high fronted guttering. Neither the BCA’s
Acceptable Construction Practise nor AS3500.3/3500.5 provides measurable requirements for
overflow to be included in guttering, and this needs to be resolved. Responsibility for maintenance
needs to be clarified as well. The Committee believes that the relevant building practitioners and
licensed contractors cannot be held responsible for overflow events that are created through
blockages caused by inadequate maintenance of guttering and downpipes. Those who wish to
minimise maintenance, should specify higher level features in the design of guttering systems but
this is considered to be above the minimum standards provided by the BCA’s performance
requirements.
Recommendations:
1. That consideration be given by the Australian Building Codes Board to ensure that all
Building Solutions (especially Deemed to Satisfy solutions) that use high fronted
guttering be designed to have the capacity to accommodate the building’s location 100
year ARI.
2. That overflow requirements be stated in quantifiable and measurable terms in Deemed
to Satisfy solutions, to prove that performance of one or more options will meet the 100
year ARI.
3. In conjunction with the previous recommendation, that the Australian Building Codes
Board (including input from industry, government and consumers) give consideration to
and debate different means of meeting the above overflow requirements – such as
increasing the design capacity of high fronted guttering from the 20 year ARI to the 100
year ARI. This should include debate and consideration of the ramifications of
continuous versus location specific overflow.
4. That, recognising the responsibility for the correct installation of guttering and
downpipes under the Environment Planning and Assessment Act and the Home Building
Act 1989 lies with building practitioners and licensed contractors, to assist,
manufacturers should be required to test and publish design information including cross
sectional gutter areas and overflow rates for their preferred overflow provisions e.g. set
down below the top of the fascia clips, flashing, gutter slots, fascia-gutter spacers,
inverted nozzles, rain water heads etc.
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