NCC Waterproofing Requirements

The National Construction Code (NCC) is Australia’s primary set of technical design and construction provisions for new builds. This includes everything from energy efficiency to waterproofing, giving developers and project owners clear performance requirements that set the minimum level required for safety, health, accessibility, and sustainability.

If you’re currently planning a new build or are overseeing the development of houses or apartments, you might be wondering what the exact requirements are for waterproofing. Explore everything you need to know below.

Why is waterproofing so important?

Waterproofing a home is incredibly important for a number of reasons:

• Structural integrity: Waterproofing creates a barrier that protects the house’s foundation and walls from moisture.
• Preventing mould growth: Waterproofing prevents water from seeping into hidden cracks and crevices, where mould can grow and cause health issues.
• Energy efficiency: Waterproofing can increase thermal insulation which can maintain inside temperatures to prevent energy costs.

Key areas covered by the new NCC waterproofing requirements

Looking through the NCC waterproofing requirements, it can be difficult to dictate what’s new within the existing requirements. We’ve summarised the main changes below for your convenience:

Internal waterproofing changes

There have been changes to both internal and external waterproofing, including a complete restructuring of provisions. Some of the new requirements have been added to include the waterproofing of shower walls to the height of 1800 mm, along with provisions for WCs with handheld bidet spray installation.

There’s also a re-introduction of the wet area Acceptable Construction Provisions (ACP) which was last seen in the BCA 2011. This gives you the option to use it as an alternate compliance option to AS 3740, which is the standard that provides guidance on waterproofing in wet areas.

Other changes for waterproofing

The revised NCC 2022 waterproofing requirements include changes to the classification of different types of showers and updated figures for the treatment of shower areas and strip drains. Waterproofing requirements have become more extensive and strict for areas like shower walls. You can choose from a greater range of waterproof and water-resistant substrates, along with surface materials. This gives you a greater range of contemporary design options when developing your buildings.

Fibre cement sheeting can now be considered a water-resistant substrate (which it wasn’t previously) when it’s supported on a structural floor. Pre-treated concrete that’s resistant to moisture can also be used as a surface material, and even include cable floor heating treatment.

Falls to floor wastes

The NCC 2022 requires falls to be provided with all floor wastes located in a wet area. This is applicable no matter whether the floor waste is ‘required’ under the wet area waterproofing standards, a ‘non-required’ floor waste in the bathroom area, or is simply used to streamline the plumbing design.

All floor wastes in wet areas require a gradient to the waste of between 1:50 and 1:80 within the surrounding floor.

External waterproofing changes

The NCC 2022 has now clarified things that were previously considered a grey area, including where waterproofing provisions apply when external waterproofing standard AS 4654.1 & 2 has been adhered to.

The Standard applies to flat roofs, roof terraces, balconies, and exposed joints in roofs located above internal spaces within a building. You can now find specific exemptions for external waterproofing in housing construction within the NCC Vol 2 Clause H2D8.

Changes to plumbing and drainage

The revised NCC adopts a new plumbing standard AS/NZS 3500.2:2021, which includes changes for typical connection arrangements for graded branch drains that enter the main drain. This includes a DN100 branch drain to connect at an elevated 15-degree angle, which wasn’t previously a requirement.

If your building doesn’t have a sanitary drainage system to accommodate this change, you may find that the first-floor ceiling joists aren’t deep enough to allow for the added gradient.

Residential waterproofing requirements

The waterproofing requirements set out by the NCC for residential areas are extensive, and you can read all about them here. The main changes focus on the shower and bath areas. We’ve summarised the changes below in case you don’t have time to comb through them:

10.2.1 Wet areas

• Building elements within wet areas must be protected with a waterproofing system
• Waterproofing systems must either be waterproof or water-resistant in accordance with 10.2.2 to 10.2.6

10.2.2 Shower areas

• If your shower area has a hob, step down or level threshold, it needs to adhere to the following rules:
  • The floor must be waterproof
  • The walls must be waterproof not less than 1800 mm above the floor substrate
  • Wall junctions and joints must be waterproof not less than 40 mm on either side of the junction
  • Wall and floor junctions must be waterproof
  • Penetrations within the shower area must be waterproof
• A shower with a preformed shower base must also comply with the above requirements unless they’re not applicable

10.2.3 External shower areas

The requirements for the area outside the shower area are dependent on the material it’s made from.

• For concrete, compressed fibre cement, and fibre cement sheet flooring: The floor must be water-resistant
• For timber floors including particleboard, plywood, and other timber: The floor must be waterproof
• Wall and floor junctions must be waterproof and, where flashing is used, with a horizontal leg of more than 40 mm

10.2.4 Areas adjacent to baths and spas without showers

The requirements for areas adjacent to baths and spas depend on their material:

• For concrete, compressed fibre cement, and fibre cement sheet flooring: The floor must be water-resistant
• For timber floors including particleboard, plywood, and other timber: The floor must be waterproof
• Tap and spout penetrations must be waterproof when they occur on horizontal surfaces

If your bath or spa is freestanding, the requirements for waterproofing adjacent areas:

• Walls must be water-resistant:
  • To a height of now less than 150 mm above the vessel, for the extent of the vessel, where the vessel is within 75 mm of a wall; and
  • for all exposed surfaces below the vessel lip
• Wall junctions and joints must be water resistant within 150 mm above a vessel with the extent of the vessel
• Wall and floor junctions must be waterproof for the extent of the vessel

If your bath or spa is inserted, the following applies:

• All floors and horizontal surfaces:
  • Any shelf area adjoining the bath or spa must be waterproof and include a waterstop under the vessel lip
  • There aren’t any requirements for the floor underneath a bath or spa
• All walls must be:
  • Waterproof to not less than 150 mm above the lip of a bath or spa
  • There aren’t any requirements for the floor underneath a bath or spa
• All wall junctions and joints:
  • Waterproof junctions within 150 mm of a bath or spa
  • There aren’t any requirements for the floor underneath a bath or spa
• All tap and spout penetrations must be waterproof where they occur on horizontal surfaces

10.2.5 Other areas

For walls adjoining other vessels, such as a sink or a laundry tub, the following must be adhered to:

• Walls must be water-resistant to a height of not less than 150 mm above the vessel where the vessel is within 75 mm of a wall
• Waterproof wall junctions where a vessel is fixed to a wall
• Waterproof tap and spout penetrations where they occur in surfaces required to be either waterproof or water-resistant

For laundries and toilets, the following must be adhered to:

• The floor of the room must be water-resistant
• Wall and floor junctions must be water-resistant, and where flashing is used, the horizontal leg must not be less than 40 mm

For WCs with handheld bidet spray installations, the following must be adhered to:

• The floor of the room must be waterproof
• Walls must be
  • Waterproof within a 900 mm radius from the wall connection of the handheld bidet, to a height of not less than 150 mm above the floor
  • Water-resistant within a 900 mm radius from the wall connection of the handheld bidet to a height of not less than 1200 mm above the finished floor level
• Wall junctions within a 900 mm radius from the wall connection of the handheld bidet must be waterproof
• Wall and floor junctions within a 1000 mm radius from the wall connection of the handheld bidet must be waterproof
• Penetrations in the WC area must be waterproof

You can read more about waterproofing systems, materials, and extra equipment by reading the full NCC 2022 here.

What are the key performance requirements?

The key performance requirements have been adapted to accommodate the new waterproofing requirements. Performance requirements are the minimum accordance you need to meet in regard to the new changes. Here’s everything you need to know:

Shower walls

Shower walls must be waterproofed to a minimum height of 1800 mm above the finished floor level, or 50 mm above the shower rose – whichever is higher.

Wall junctions and joints

Wall floor junctions and joints must be waterproofed for at least 40 mm on either side of the junction.

Floor plane gradient

The floor plane needs to have a minimum continuous fall of a floor plane to waste of 1:80, with a maximum gradient of 1:50.

Waterproof membranes

These must be graded to the drain waste puddle flange.

Shower area step down

The highest finished floor level in the shower needs to be lower than the finished floor level outside of the shower, so there’s a step down when you’re getting out of the shower.

Materials

The NCC specifies the specific waterproof and water-resistant materials that are accepted for walls and floors in wet areas, so these must be adhered to to make sure you’re meeting the key performance requirements.

How do these changes impact building costs?

The major changes involve materials, how large each waterproof area needs to be, and external waterproofing. How much these changes impact your building costs will depend on what processes you’re currently using. For example, if you’re already waterproofing your shower areas up to 1800 mm, then you might not have to spend any extra on waterproof materials and labour costs.

However, if you’ve been taking advantage of the more lenient ‘water-resistant’ terminology instead of ‘waterproof’, which the NCC seems to be pushing much more now, you’ll most likely have to spend more on waterproofing materials. Your team will most likely need extra training in how to use these waterproof materials and processes, which can also increase building costs.

Compliance pathways

Compliance pathways are put in place when your current building work doesn’t adhere to the NCC requirements. Instead of instantly being shut down, you might be able to use a compliance pathway to get the NCC on board anyway. There are three compliance pathway options to follow:

1. Performance solutions

Performance solutions are achieved by directly demonstrating compliance with all appropriate performance requirements. This will be assessed by one or more of the following:

• Evidence of suitability
• Expert judgement
• Verification methods
• Comparison with Deemed-to-Satisfy provisions

Performance solutions are more flexible and often allow for alternative methods or materials to be used. As long as the end result meets or exceeds the performance requirement set by the NCC, there shouldn’t be an issue.

2. Deemed-to-Satisfy solutions

Deemed-to-Satisfy solutions are prescriptive where compliance is achieved by following specific methods or by using particular materials outlined by the NCC. As long as you follow the Deemed-to-Satisfy provisions, you shouldn’t run into any speed bumps.

These are assessed by one or more of the following:

• Evidence of suitability
• Expert judgement

3. Combination of a performance solution and a Deemed-to-Satisfy solution

If neither of the first two compliance pathways applies to you, you can also blend them together and combine a Deemed-to-Satisfy with a performance solution to show your compliance with the performance requirement.

The compliance will then be assessed by one or more of the following:

• Evidence of suitability
• Expert judgement
• Verification methods
• Comparison with Deemed-to-Satisfy provisions

Common waterproofing issues & how to avoid them

Waterproofing is a huge deal when developing new builds. One wrong move and your property could be susceptible to structural integrity, mould, and more. Here are some of the common waterproofing issues and how you can avoid them:

• Water-resistant vs waterproof: These terms are often incorrectly used interchangeably, leading to water getting into places it shouldn’t. While frustrating, the NCC requirements are put in place for a reason and they’re to protect both homeowners and building structures. Make sure you adhere to the minimum performance requirements to keep waterproofing issues to a minimum.
• Incorrect installation: If appliances and waterproof materials aren’t installed properly or the wrong prep work is carried out, waterproofing efforts can fail. Make sure your contractors and their teams are all highly skilled and up to the task to avoid installation having to be ripped up and replaced.
• Using incorrect materials: Waterproofing materials aren’t all the same and most have specific applications that you’ll be advised to use them on. We recommend finding a trusted supplier with excellent knowledge of the subject to make sure they’re giving you the best advice for what you need.
• Lack of ventilation: A lack of ventilation in high-moisture areas, like bathrooms, is a huge red flag for waterproofing issues. The lack of ventilation can cause humidity to build up and lead to water damage, which can affect your waterproofing efforts in the long run.

Our tips for ensuring NCC waterproofing compliance

Here are some of our favourite tips and tricks to make sure you’re complying with NCC’s waterproofing requirements:

• Ultilse a building certifier who is fluent in the current NCC requirements so they can make sure your plans are up to standard before going ahead
• Choose suppliers and contractors wisely to make sure they can be trusted with completing the work up to standard
• As much as possible, use waterproof materials and solutions rather than water-resistant alternatives, as these often aren’t as reliable
• Don’t cut corners to accommodate new costs; comb through your budget to redirect money into waterproofing your development reliably
• Read the NCC requirements and make sure you’re up to date with what’s expected of you rather than solely relying on others

Explore other NCC requirements and regulations

• NCC changes 2024
• NCC energy efficiency requirements
• NCC floor waste requirements class 1
• NCC handrail requirements
• NCC disability access requirements

Get free advice from an experienced building broker on your new build

Buildi strives to make the lives of our clients as easy as possible through our expert building broker knowledge. This includes all things NCC, so if you’re still unsure about your waterproofing requirements or need some extra advice, we’re here to help. Get in touch with us today at 1300 947 132 or through our Contact Form to get free advice right away.