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  • David Previte

Design and Building Waterproofing Details in 2021

In July 2021, many legal requirements for construction professionals come into effect. These changes have been on the cards for some time but with the regulations for the NSW Design and Building Practitioners Act 2020 recently made available, more is now known on the Act's application. However, there has been some ambiguity around waterproofing in the regulation and where it fits in the legislation despite being listed as a priority building element in the Act.

As the Building Commissioner has stated, the NSW Government is pushing for 'design, then construct', noting that details for wet areas have too commonly been missing from issued for construction drawings. So for any project, the onus is on the principal design practitioner (architect or engineer) to design a building that is compliant with the National Construction Code (NCC) and a multitude of adopted Australian Standards. Then a principal building practitioner (builder) to execute those plans in construction and document compliance.

These plans are to be submitted to the NSW Planning Portal and will involve a compliance declaration stating that each building element is compliant and integrates with other aspects of the building. For the principal design practitioner, this is at the stage of obtaining the construction certificate and for the principal building practitioner this is part of the occupation certificate application. During construction, between each of these submissions, variations are to be documented and submitted explaining the area of the building and why such changes are occurring.

When it comes to waterproofing, the only reference in the Design and Building Practitioners Regulation 2021 is that an exemption applies under the legislation for waterproofing applications to alterations in a single dwelling in a wet area. So apart from a renovation to a building presumably many years after construction, every other waterproofing application is to be considered under the Act. That is every bathroom, laundry, balcony, rooftop, podium, planter box, tank, swimming pool, retaining wall, tank or other area where waterproofing is applied. Unbeknownst to many in the remedial space, this legislation also applies to their work.

The aim is to have all buildings constructed in a way that achieves the requisite performance targets defined in the NCC. The regulation's first clause outlines that where a design does not adhere to the deemed-to-satisfy provisions, a report detailing a performance solution needs to be prepared to verify compliance with performance requirements. The many construction practices that have become widely popular but are not listed in the deemed-to-satisfy provisions of the NCC will require performance solution documentation as per NCC 2019 Part A2.2. Pavers on pedestals and flush transitions on balconies for aesthetic or NDIS requirements are two that are most prevalent where waterproofing is applied.

The regulation provides 18 design practitioner registration classes including various types of fire, facade, drainage, mechanical and structural specialties though there is no classification for waterproofing practitioners. With waterproofing defects commonly acknowledged as the single largest source of defects this is surprising and begs the question of where this responsibility falls?

Based on our interpretation and discussions with industry professionals, this responsibility falls with the architectural design practitioner. We are currently seeing waterproofing designs being developed through collaboration between architectural design practitioners, builders and specialist waterproofing consultants to ensure the design is both buildable and achieves compliance with NCC requirements. In this process it is important to remember that generic section details developed by material suppliers can be a starting point but are not project specific.

Compliance inspections and onsite testing reports during construction provide the support for the principal building practitioner to make declarations in submitting for the occupation certificate. Both quantitative measurements and testing and qualitative inspections are means to quantify installation methods and

The commencement of this Act is one of a number of changes in reference documents that will impact waterproofing over the next couple of years with changes and updates afoot for AS3740 and the NCC.

If you or someone you know requires assistance in navigating the requirements of the legislation in waterproofing, whether they are an architect, builder or other industry professional, please call Waterproofing Integrity on 1300 025 944 or email

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