Alternate compliance options for waterproofing

The National Construction Code (NCC) 2022 was recently released and both Volume One and Volume Two contained a range of waterproofing changes for both internal and external waterproofing including a complete restructuring of the provisions. 

The provisions for Volume One are now included at Part F2 - Wet areas and overflow protection and a new Specification 26 - Waterproofing and water-resistance requirements for building elements in wet areas.

The provisions for Volume Two are now included in Part H4D2 Wet areas and H4D3 Materials and installation of wet areas components and systems and through Section 10.2 of the ABCB Livable Housing design Standard.

What are the wet area changes for Volume Two?

One of the major changes for Volume Two is the re-introduction of the prescriptive DTS Provisions as a stand-alone set of provisions that can be adopted as an alternate compliance option to AS 3740.

These provisions are based off the wet area Acceptable Construction Provisions (ACP) that was last included in BCA 2011 with some further amendments to reflect some more contemporary matters.

HIA was instrumental in getting this back into the NCC Volume Two and members have raised many issues since this was removed and took a number of years of advocacy to get agreement to include these provisions back into the NCC.

HIA support the re-introduction of the wet areas and other ACP as it provides a set of provisions separate to Australian Standards which was the original intent when the Housing Provisions were first developed.

The changes don’t replace AS 3740 as a DTS Solution, but rather the new provisions in Volume Two provide an alternate compliance option.

Other Volume Two changes

Other changes in Volume Two that will apply regardless of using AS 3740 or the Volume Two DTS Provisions in Part 10 of the Housing Provisions, include:

• Adoption of the revised AS 3740: 2021 - Waterproofing of domestic wet areas
• Walls of a shower area must be waterproofed to a height of 1800mm
• Provisions for WCs with a hand-held bidet spray installation
• Fibre-cement sheeting supported on a structural floor an allowable water-resistant substrate (as opposed to only compressed cement sheet)
• Concrete that has been treated to resist moisture can be used as a surface material

Changes to falls for floor wastes

One specific change relating to falls to the floor waste outside of the shower or in a laundry, has been a long discussed matter with lots of differing views.

The change to clause 10.2.12 construction of wet area floors – falls states:

Where a floor waste is installed—

(a) The minimum continuous fall of a floor plane to the waste must be 1:80; and

(b) The maximum continuous fall of a floor plane to the waste must be 1:50.

This amendment has changed the requirement to now prescribe that where a floor waste is installed in a dwelling, including in a laundry or outside of the shower, that the floor to that waste must be falled to permit drainage to that waste.

Previously this provision only applied where the floor waste was required by the NCC or AS 3740.

Although, it’s important to note that the clause doesn’t prescribe that a floor waste must be installed in building in situations other than in the shower area, rather where one is installed the floor needs to fall to that waste.

What are the wet area changes for Volume One?

Specification 26 prescribes what areas are required to be either waterproof or water resistant and to what extent - Specification 26 replaces the current Table F1.7 with additional requirements.

Consistent to what is currently required for Class 2 and 3 building and a Class 4 part of a building, building elements in wet areas must be water resistant or waterproof in accordance with Specification 26 and comply with AS 3740.

The revised AS 3740 2021 will be the referenced Australian Standard for Waterproofing of domestic wet areas to be included in NCC 2022 and changes include:

• More extensive waterproofing requirements for shower walls
• More choice for wet area waterproof and water-resistant substrates and surface materials
• Provision for a polished concrete in situ shower base
• A more comprehensive Appendix A which includes more design considerations and design solutions in wet-area waterproofing

In a Class 5, 6, 7, 8 or 9 building, building elements in a bathroom or shower room, a slop hopper or sink compartment, a laundry or sanitary compartment must be water resistant or waterproof in accordance with Specification 26 comply with AS 3740, as if they were in a Class 2 or 3 building or a Class 4 part of a building.

Specification 26 also introduces new proposed provisions for WCs with a hand-held bidet spray installation.

Adoption of revised edition of AS 3740:2021

Both Volumes One and Two adopt the revised edition of AS 3740 2021. Key changes include:

• More extensive waterproofing requirements for shower walls
• More choice for wet area waterproof and water-resistant substrates and surface materials
• More contemporary design options
• A range of editorial changes and other changes to make the provisions more clear and to overcome interpretation issues
• A range of additional figures to assist with interpretation
• Provision for a polished concrete in situ shower base; and
• A more comprehensive Appendix A which includes more design considerations and design solutions in wet-area waterproofing

Floor wastes for Class 2, 3 or 4 parts

As is currently required a Class 2 or 3 building or Class 4 part of a building, a bathroom or laundry located at any level above a sole-occupancy unit or public space must have a floor waste.

The proposed provisions for floor wastes introduce a minimum and maximum fall to a floor waste where one is installed.

External waterproofing

There are also changes to both the Volumes One and Two external waterproofing provisions and HIA will prepare a further information note on those changes. 

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