- 1. Missing or Inadequate Waterproofing Membrane
- 2. Failed or Missing Cove at the Floor-to-Wall Junction
- 3. Inadequate or Deteriorated Silicone Joints
- 4. Incorrect Falls on the Shower Floor
- 5. Penetrations Through the Membrane Not Sealed
- 6. Membrane Incompatibility or Poor Substrate Preparation
- 7. Shower Screen Installed Before Waterproofing Was Completed
- When a Leaking Shower Becomes a Legal Matter
- What to Do If Your Shower Is Leaking
- FAQs
A leaking shower is one of the most common building defects in NSW homes — and one of the most misunderstood. Homeowners spend months re-grouting and resealing tiles, only to watch the water come back. That's because the visible damage is almost never the actual problem.
The real cause is usually buried beneath the tiles, hidden behind the walls, or sitting at a junction that was never properly sealed during construction. Knowing where waterproofing fails — and why — puts you in a much better position when it comes to repairs, insurance claims, or any legal action down the track.
Here are the seven most common waterproofing failures found in NSW shower enclosures.
1. Missing or Inadequate Waterproofing Membrane
The membrane is the foundation of any shower. It sits beneath the tiles and stops water from reaching the substrate below.
In NSW, the relevant standard is AS 3740:2021 (Waterproofing of Domestic Wet Areas). It sets out minimum coverage requirements: the full floor, at least 150mm up the walls from the floor, and full coverage behind wall-mounted fixtures.
When a membrane is applied too thinly, missed in corners, or skipped entirely on wall sections, water finds a path through. You may not notice for 12 to 24 months — by which point the substrate is already damaged.
This is the single most common defect identified during Awesim's forensic waterproofing inspections.
2. Failed or Missing Cove at the Floor-to-Wall Junction
The cove is the curved or angled fillet at the base of the shower wall where it meets the floor. Its purpose is straightforward: prevent water from pooling in a sharp corner, which is a point of concentrated stress in any membrane.
Without a proper cove, the membrane has to fold at a 90-degree angle. Over time, that fold cracks. Water enters and tracks horizontally behind the tiles.
Many builders skip the cove to save time, or apply it inconsistently. Either way, the junction fails and the leak begins.
3. Inadequate or Deteriorated Silicone Joints
Silicone sealant is used at movement joints — the gaps between the shower screen and tiles, at internal corners, and at the base of the screen. These joints flex as the building moves and as temperature changes cause materials to expand and contract.
Silicone doesn't last forever. In a wet area, it typically holds for 5 to 10 years before it starts to crack, shrink, or lose adhesion. When it fails, water bypasses the joint and enters the wall cavity.
Cheap silicone applied during original construction is a common culprit in homes built in the 2000s and 2010s. From the surface it looks intact, but it has already separated from the tile edge underneath.
4. Incorrect Falls on the Shower Floor
Water needs to drain toward the waste outlet. AS 3740 specifies a minimum gradient, and the floor must slope consistently in that direction.
When the fall is too flat, or runs away from the waste, water pools against the wall junction. That standing water puts sustained pressure on the membrane and silicone joints — and even a correctly installed membrane will eventually give way under constant hydrostatic load.
Tilers sometimes create a flat floor for aesthetic reasons, or because the substrate wasn't properly prepared before tiling. The result is a shower that looks fine but drains poorly and fails early.
5. Penetrations Through the Membrane Not Sealed
Every pipe, tap spindle, and waste fitting that passes through the waterproofed surface is a potential entry point for water. Each penetration must be sealed with a compatible sealant or flashing collar before tiling begins.
When penetrations are left unsealed — or when the sealant isn't compatible with the membrane system used — water tracks down the pipe and into the wall or floor cavity. This type of leak is particularly hard to trace because the water can travel a significant distance from the source before it shows up as visible damage.
6. Membrane Incompatibility or Poor Substrate Preparation
Not every membrane bonds to every substrate. Sheet membranes, liquid-applied membranes, and cementitious systems each have specific requirements for surface preparation, priming, and application conditions.
Apply a liquid membrane to a dusty, damp, or contaminated surface and adhesion fails. Use a membrane not rated for wet areas, or apply it over a substrate that moves, and it will delaminate.
This failure mode is especially common in renovations where new waterproofing is applied over existing tiles without stripping them first, or where the substrate is a compressed fibre cement sheet that has already absorbed moisture.
7. Shower Screen Installed Before Waterproofing Was Completed
Sometimes a shower screen is installed before the membrane has been applied to the full height required by the standard. The screen base sits directly on unprotected substrate, and the membrane is then applied only to the visible areas around it.
Water that travels under the screen base reaches unprotected material immediately. The damage typically shows up as efflorescence — white salt deposits — on tiles near the screen base, or as staining on the ceiling of the room below.
This is a construction sequencing defect, not a maintenance issue. Fixing it properly means removing the screen and reinstating the waterproofing correctly.
When a Leaking Shower Becomes a Legal Matter
A leaking shower caused by defective workmanship is a building defect under the Home Building Act 1989 (NSW). You have rights — including the right to have the defect rectified or to claim compensation.
If your builder disputes the defect, denies liability, or has already walked away from the job, you may need to take the matter to NCAT (the NSW Civil and Administrative Tribunal). At that point, an independent forensic inspection report becomes essential.
A forensic waterproofing inspection goes beyond locating where the water is appearing. It documents the cause, traces the failure back to the specific workmanship or materials issue, and produces a written report that can be used as evidence.
Awesim Building Consultants conducts forensic waterproofing inspections on-site across NSW, with offices in Sydney, Tamworth, and Tweed Heads. Reports are prepared to satisfy UCPR Schedule 7 — the standard required for expert evidence in NSW courts and NCAT proceedings.
If the dispute proceeds to a hearing, the forensic report forms the basis of an expert witness report. Awesim has been preparing expert witness reports for NSW courts and NCAT since 1996.
What to Do If Your Shower Is Leaking
Step 1: Stop patching it yourself. Re-grouting or applying surface sealant over a failed membrane delays the investigation and can make the underlying defect harder to document accurately.
Step 2: Document everything. Photograph the visible damage, note when it started, and keep any correspondence with your builder.
Step 3: Get an independent inspection. A forensic waterproofing inspection identifies the cause, not just the symptom. That distinction matters enormously if you end up at NCAT or in court.
Step 4: Know your time limits. Under the Home Building Act 1989, the statutory warranty period is 6 years for major defects and 2 years for non-major defects from the date of completion. Don't wait.
If you're unsure where your situation sits, a free initial consultation is available by calling 1800 293 746.
FAQs
Why does my shower keep leaking even after I've resealed the grout?
Grout is a filler between tiles, not a waterproofing material. If the membrane beneath the tiles has failed, resealing the grout surface won't stop water from entering the substrate. The leak will return until the membrane is properly reinstated.
How do I know if my shower has a waterproofing defect or just normal wear?
Normal wear affects surface materials like grout and silicone joints. A waterproofing defect involves the membrane beneath the tiles or the structural junctions of the shower enclosure. Signs of a defect include water appearing in rooms adjacent to or below the shower, efflorescence on tiles, soft or hollow-sounding tiles, and persistent damp smells that don't resolve after the shower dries.
Can I claim for a leaking shower under the NSW Home Building Act?
Yes — if the shower was constructed or renovated by a licensed builder and the defect is caused by defective workmanship or materials. The statutory warranty period is 6 years for major defects and 2 years for non-major defects from the date of completion. A forensic inspection report will help establish whether the defect qualifies.
What does a forensic waterproofing inspection involve?
It's an on-site examination of the shower enclosure and surrounding areas. The inspector uses moisture meters, thermal imaging, and visual assessment to identify the source and cause of the failure. Findings are documented in a written report that explains the defect, its cause, and the rectification required.
Do I need an expert witness report for an NCAT waterproofing dispute?
If you're making a building defect claim at NCAT and the builder disputes liability or the cost of rectification, an independent expert witness report significantly strengthens your position. The report must comply with UCPR Schedule 7 to be accepted as expert evidence. Without it, you're relying on your own account against a builder who may have their own expert.
How much does a forensic waterproofing inspection cost?
Fees vary depending on the complexity of the inspection and whether a formal report is required for legal proceedings. Expert reports in NSW generally range from $2,000 to $10,000, with approximately $4,500 typical for a standard engagement. A free initial consultation is the best starting point to understand what your situation requires.
Can Awesim inspect a property outside Sydney?
Yes. Awesim operates from three offices across NSW — Sydney, Tamworth, and Tweed Heads — and conducts on-site inspections across the state. Regional and rural properties are within scope.
A leaking shower won't fix itself. The longer you wait, the further the water spreads and the harder the defect becomes to document. If you suspect defective workmanship is the cause, an independent forensic inspection is the most direct way to find out where you stand. Start with a free consultation at awesim.com.au or call 1800 293 746.
