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

Inspectors advised that all homes except for one were not compliant with AS3500 in regard to the
adequate provision of downpipes, but then made the additional observations that the majority were
compliant with BCA performance requirements i.e. as a result of lack of evidence of water damage
from gutter overflow.
The Committee believes these were perhaps lenient interpretations of the BCA and ideally should
have checked to determine the maximum rainfall intensity that the homes had been exposed to, in
order to draw conclusions about how well the homes were meeting BCA performance requirements.
In addition, independent auditing by an expert adviser to the Committee of the calculations made by
Inspectors was undertaken on eight dwellings. Though the exact calculations made by the expert
varied from those of the inspectors, the expert still agreed with the conclusion that the houses
studied did not comply with AS3500.3 or “Acceptable Construction Practice”. It revealed
inconsistencies and inaccuracies in the calculations. The expert also said that it is hard to determine
whether or not the dwellings comply with the basic performance measure of avoiding flows into a
dwelling under the 100 year ARI – stating that gutters tend to overflow at low points thereby
reducing the load on the downpipe system and that some gutters distort under full load and the
distortion permits a discharge of water reducing the peak load. The audit report also found that
AS3500.3 provides more rather than less downpipes and guttering than the BCA’s own “Acceptable
Construction Practice” for the 20 year ARI. It would seem that the latter, in general, provides a more
lenient basis for meeting BCA performance requirements.
As a result of the above findings, there is a concern by the Committee of a lack of adherence and
understanding in industry concerning the use of Deemed to Satisfy solutions and the calculation
methods involved in specifying the gutter size and number of downpipes to suit the roof area for a
given 20 year ARI. Though evidence here is limited, there is concern about a lack of downpipes to
deal with the ARI. Whilst such problems effect the compliance of all guttering systems trying to
meet Deemed to Satisfy compliance, it is clear that high fronted guttering are more sensitive to the
effects of such problems due to the ramifications that a lack of downpipe drainage has on overflow
entry into a building. Informal overflow mechanisms – mentioned previously - may to an unknown
extent assist in mitigating the chances of such overflow.
The Insurance Council of Australia(ICA)
The ICA formally advised the Committee that there was no systemic problem their members were
able to identify in relation to high fronted guttering.
Industry Parties
Individual manufacturers, the Housing Industry Association (HIA) and the Australian Steel Institute
provided advice to the Committee that they still had (following on from meetings held in 2008) no
evidence of a systemic problem concerning high fronted guttering in NSW, or elsewhere in Australia.
The Committee was satisfied that a relatively small number of manufacturers dominated the
guttering market – each made individual representations to the Committee. A number of them
provided sales data to demonstrate that the vast majority of their sales involve high fronted
guttering i.e. high fronted gutters represent between 65-86% of the overall eaves gutter market.
Evidence was also presented by one manufacturer (by way of a historically significant advertising
brochure) that high fronted guttering have been in the market place some 40 years, since 1970. The
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