Building Codes like the “National Construction Code” (NCC) and “Australian Standards” like ‘Wet area waterproofing’ are written by the the Australian Building Codes Board (ABCB).
The ABCB is responsibe for authoring “AS 3740:2021 – Wet area waterproofing”.
The following is and exerpt from the Australian Building Codes Board website.“We ensure safe and sustainable building and plumbing systems through regulatory and non-regulatory measures, in collaboration with Australian governments and industry.
The Australian Building Codes Board (ABCB) is a standards writing body responsible for the National Construction Code, WaterMark and CodeMark Certification Schemes, and regulatory reform in the construction industry. The ABCB is a joint initiative of the Commonwealth and state and territory governments, together with the building and plumbing industries.”
The fact that the Australian Building Codes Board (ABCB) went to the trouble and expense of issuing a new version of the existing Standard in 2021, means Builders just weren’t getting waterproofing right.
The new standard is even more prescriptive and detailed than previous versions. What’s interesting about the updates to the standard is that the key changes are in fact the areas where problems are commonly found.
Across the waterproofing standard there is an emphasis on “water-stops”. Waterstops are defined as “A vertical extension of the waterproofing system forming a barrier to prevent the passage of water in a floor or other horizontal surfaces.” Usually these waterstops are aluminium angles sealed to the floor and waterproofed over, tiling is then installed around these angles. The key aspect of a waterstop is that it must protrude slightly from the finished tile surface. The waterstop forms the perimeter of the shower recess and is present below the shower screen. Waterstops also span the door opening. The shower screen is installed on top of the waterstop. The screen extends this ‘vertical extension’ up to head height. This way water is fully contained in the shower cubicle and is not able to track across the bathroom floor or out the bathroom door threshold.
Membrane section – step down shower membrane below tile screed
Membrane section – step-down shower, membrane on top of tile screed
Membrane section – level shower floor
Membrane section – hobbed shower
What are the main changes in the new standard: AS 3740:2021 – Wet area waterproofing?
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Shower walls must be completely waterproofed
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Gradient requirements for surface finishes have changed.
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Waterproof membranes must be graded to the drain waste puddle flange.
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You can avoid grading the membrane in housing if you only use the NCC (Part 10.2 Housing Provisions) and not the new AS 3740:2021
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All commercial wet areas require graded membranes and surface finishes to a drain waste.
Waterproofing Shower Walls
The new requirement mandates waterproofing the entire water-resistant wall lining in a shower area to a minimum height of either 1800 mm above the finished floor level or 50 mm above the shower rose, whichever is higher.
Wet Area floors – Gradients
Where a floor waste is installed:
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(a) the minimum continuous fall of a floor plane to the waste must be 1:80, and
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(b) the maximum continuous fall of a floor plane to the waste must be 1:50.
Membrane – Gradients
New requirement that where the surface finish (e.g. tiles) is required to drain to a floor waste, then the waterproof membrane wherever placed below those finishes must also be graded.
Are graded waterproofing membranes required in every wet area?
Membrane grading requirements can be applied differently between AS 3740 & NCC Volume 1 & 2.
In Volume 2 residential you can choose to disregard AS 3740 entirely and use all of Section 10.2 that does not require graded membranes to a drain waste. For Volume 1, commercial buildings and units there is no opting out of the graded membrane requirements in any wet area with a drain waste.
This is a key aspect of the domestic code.
Membrane section – floor drain detail
Membrane section – door threshold waterstop angle
Membrane section – internal corner bond breaker
