Waterproofing and water-related building defects cost Australia $4 billion annually. These issues consistently rank as the most common building problems in each state. The Acil Allen Impact Analysis report (February 2024) highlights this significant financial impact.
In this article, Byron Landeryou, the Founder and Managing Director of Waterproof Awareness and Industry Best Construction, will detail why we’re getting waterproofing so wrong and how to get it right with a 7 stage inspection process.
P.S. Are you ready to speak confidently with your trades and master the ins and outs of waterproofing? Don't miss the incredible offer waiting for you at the end of this article!
Why are these defects so prevalent?
It is expected that each trade will know the compliance requirements of the Building Code, Australian standards and product information.
For decades, many in the construction industry have not seen waterproofing as a significant part of the building process. Statements like “waterproofing is just glorified painting—just open a bucket and paint it on” or “my tiler does the waterproofing and they’re all over it” are common.
It is extremely common to see critical waterproofing details left off building plans and drawings or detailed incorrectly.
It's important to understand that the Australian standards are the minimum requirements.
Alarmingly, many waterproofing installations don't meet these minimum requirements as many tradespeople may have never read the Australian standards related to their trade, having learned their skills on-site from other tradespeople and usually half-day product manufacturers' training.
How do I know this?
I started on the tools as a wall & floor tiler/ waterproofer back 1999, and I learned my trade the same way as most other tradies.
l had never really looked at the standards until I began teaching at a trade school back in 2014 and discovered I was doing certain elements of my job incorrectly and not to code.
Since being off the tools full-time for over ten years now, I've focused on waterproofing codes and standards, wet area design compliance, and assessing hundreds of failures on-site as part of my construction training and consulting businesses.
At Waterproof Awareness and Industry Best Construction, we are frequently engaged to attend sites that are partway through construction or post-construction with water-related defects.
We often find two consistent themes:
- Either the builder has constructed the building in accordance with the building plans, and the wet area has been designed incorrectly, or
- Not all of the critical details are listed on the plans, leading the builder and trades to make it up as they go.
These two scenarios commonly lead to either a non-compliant building or a water-related building defect with everyone scratching their heads.
How can we get it right?
The waterproofing or wet area construction process requires a Multi-Stage Inspection process.
Here’s an outline of the key steps I deem necessary to ensure successful outcomes for waterproofing your internal wet areas and balconies.
First Stage: Design Review
When interpreting the NCC and encountering the phrase “deemed-to-satisfy solution,” this refers to the applicable Australian standards used for construction as a compliance pathway. Currently, Australia has AS 3740:2021 for waterproofing of domestic wet areas, AS 4654:2012 Parts 1 & 2 for waterproofing external above-ground wet areas.
Engage an expert waterproofing consultant to assist with a design review of your plans.
An experienced waterproofing consultant should be able to assess whether the overall design of the wet area will work functionally and complies with the performance requirements of the Building Code of Australia (BCA), also known as the National Construction Code (NCC).
I must add that the design must also be buildable, and it is not uncommon to see a great-looking design, but trying to build it is unachievable.
In short, our design must ensure water within wet areas is properly collected, redirected, and drained, protecting the health and amenity of the occupants.
I cannot stress enough the importance of ensuring the design is correct and that the critical details are clearly listed on the plans; otherwise, failure is imminent even before construction has commenced.
Second Stage: Product Compliance
From my experience, it is rare to see a product fail, but that is not to say it cannot happen.
It is more common to see waterproofing systems fail because the installer has used a variety of different products to make up the system. Waterproofing installations comprise multiple different elements, such as porous and non-porous primers, sealant for fillets and bond breakers, detail bandage for junctions and penetrations, and the waterproof membrane itself.
To legally distribute these products, a manufacturer must have all these elements tested to ensure they are suitable to use in Australian conditions and that each element is compatible to make up the waterproofing system.
If your installer is mixing and matching different products, this can lead to failure and most certainly void the manufacturer’s warranty.
It is paramount that for any waterproofing installation, you are supplied with all of the product technical data information, including laboratory test results that verify compliance to be used in Australia.
Third Stage: Substrate Compatibility and Preparation
The wall and floor linings, aka substrates, must also be tested for suitability with Australian conditions. Generally, the waterproofing product manufacturers' technical data sheets will list the variety of different substrates that the waterproof membrane will be compatible with.
It is extremely common to see poorly installed wall and floor linings and that everything will be okay as the waterproofing and the tiling will cover it up.
It's recommended that the substrate installation guides are strictly followed to ensure that substrates have been correctly prepared for the waterproofing membrane installation.
The waterproof membrane isn't designed to fix poor workmanship of the substrate installation, and when the membrane has been installed to repair a substrate, this places a huge strain on the waterproof membrane that commonly leads to failure.
Waterproof membranes aren't designed to fix substrates. I use this phrase: The substrate must be considered the first layer of the membrane installation.
Fourth Stage: Waterproofing Membrane Installation
By the time you reach this stage, your wet area designs must comply with codes and standards, be functional, and have established substrate and membrane preparation and installation requirements.
You should also know exactly where your waterproofing membrane will start and stop.
The product technical data sheet should list key information such as suitable moisture content in your substrate before waterproofing, the correct primer to use, installing fillets and bond breakers correctly, measuring the Wet & Dry Film Thickness of the membrane, and ensuring proper detailing and termination of the membrane at perimeters, expansion joints, penetrations, outlets, and any water stop angles.
Fifth Stage: Monitoring and Testing During Installation
All waterproofing installations require many steps to be undertaken correctly, so establishing a monitoring and testing schedule during the process is essential.
This information should be set up in an easy-to-follow Quality Control plan which lists key checkpoints to follow, what photos should be taken, and hold points that allow each party to confirm the work has been completed to plan.
Creating a portfolio of evidence displaying what has been done before being covered with any overlay finishes.
We help our clients develop this approach which eliminates the blame game, going back for reworks, and proves to your clients that you are committed to the highest level of workmanship and are a trustworthy operator.
Sixth Stage: Post-Installation Testing
Post-installation testing is generally conducted before covering the membrane.
Manufacturers will specify time frames before post-install testing can be conducted as this will allow for any liquid products to cure and form an impervious or waterproof coating.
For example, the product technical data sheet should list the appropriate hours or days required to wait before flood testing can occur. Other common testing methods include Electronic Leak Detection, Ultrasonic Dry Film Thickness testing, and Seam probe testing, depending on the membrane system installed.
It is not uncommon to see a combination of these tests used to test a waterproofing installation. Once testing is completed, any defects should be marked for repair.
If the waterproofing installation passes the test, it should be documented, and approval given for the next stage of work to commence.
All parties should be given the opportunity to confirm they are happy for the works to proceed.
Seventh Stage: Protection and Handover
Once the membrane has been assessed and approved for the next stage of work, it's crucial to protect it and manage the handover correctly.
For example, if floor tiles will cover the membrane, traffic over the area should be minimised to avoid contamination and damage from other trades, as even a small hole can lead to significant failure.
Consider this: Have you ever seen an electrician’s wire cuttings sit on a completed bathroom membrane? Or allowed your cabinet maker to sit the sharp edges of the vanity on the exposed membrane?
If so, I can almost guarantee you that the membrane was punctured prior to tiling. This can be a challenge with multiple trades on site, so barricading and protection measures must be implemented immediately after testing.
Ongoing Maintenance Strategy
All building products, including waterproof membranes, have a service life and require ongoing maintenance to function as designed.
Exposed membrane systems need regular maintenance inspections to ensure longevity. Adhering to an ongoing and periodic maintenance schedule significantly reduces the risk of serious failure.
Think about what happens to your car if you don't regularly maintain it. The same principle applies to waterproof membranes and wet areas to ensure our building elements do not deteriorate and go mouldy.
Maintenance inspections will save you thousands of dollars, avoid the psychological stresses caused by going back for rework, and keep the property safe and healthy.
In Summary
Ensuring the integrity of your wet areas through proper design, product compliance, substrate preparation, membrane installation, and rigorous testing and monitoring is paramount.
By following these stages meticulously, you can safeguard against common pitfalls and failures in waterproofing systems.
It is crucial to engage experts to ensure you adhere strictly to standards, and maintain a thorough quality control plan.
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About the Author:
Byron Landeryou, the Founder and Managing Director of Waterproof Awareness Pty Ltd and Industry Best Construction, boasts over 20 years of expertise in the construction industry as a skilled wall/floor tiler, waterproofing subcontractor and now expert consultant. Additionally, he brings over 10 years of experience as a qualified trainer and assessor, sharing his extensive knowledge and skills in the field.
Byron has shared his extensive waterproofing expertise with over 3,500 students, including architects, associations, building surveyors, builders, product manufacturers, and tradespeople. Our training programs, grounded in the latest industry data, trends, and issues, provide a robust knowledge base to support all parties involved in the waterproofing of buildings and addressing failures.
