How Missing Sealant Caused Major Water Damage
A Small Shower Defect That Caused Bigger Water Damage
On this bathroom job in Agnes Water, the first sign of trouble was not inside the shower recess itself. It showed up on the adjacent wall outside the shower, where the MDF skirting board had become moist and swollen.
This sort of issue can point to a few different causes. It could be failed waterproofing, a leaking pipe, or water escaping from somewhere else in the shower area. Before jumping to conclusions, we worked through the problem properly to find the real cause.
What We Found
The defect was behind the hot and cold tap handles inside the main bathroom shower recess. There was no silicone seal behind the tap flanges, which meant water was able to enter through the tile penetrations and track into the wall cavity.
This is a defect because wet area penetrations must be sealed to prevent moisture ingress behind the tiled surface. If left unresolved, this can lead to mould growth, swelling of wall linings or skirtings, deterioration of materials, and breakdown of the waterproofing system.
In domestic wet areas, penetrations are required to be adequately sealed in accordance with AS 3740:2021 – Waterproofing of domestic wet areas.
How We Diagnosed the Problem
Because the skirting on the wall adjacent to the shower was already showing signs of moisture damage, we needed to work out exactly where the water was coming from.
We first used our moisture meter and thermal equipment while running the hot water to check whether there was an active leaking tap or pipe issue. That ruled out a leaking tap.
We then carried out a balloon flood test to confirm whether the shower hob and base were holding water. The shower passed that test, which told us the issue was likely not coming from the base of the shower.
After that, I quickly realised I had made an easy mistake by not first checking whether the tap flange had been waterproofed and siliconed around the tap penetration. At the same time, the shower head had a leak which was allowing water to run down the tile face.
Once those earlier possibilities were ruled out, the issue became clear. Because the tap penetrations had not been sealed behind the flanges, the leaking water was able to enter the wall through the openings, track down the pipework, and eventually present on the opposite side of the wall where the MDF skirting had swollen.
Why the Problem Occurred
The main cause of the problem was missing sealant behind the shower tap flanges.
This is the kind of issue that can easily be missed because the flange hides the penetration and everything can look fine from the outside. But if that opening has not been sealed properly, water can still get in behind the tile. Once water finds a path, it can travel a long way before it becomes visible.
In this case, the leaking shower head made the issue worse by feeding more water down the tile face and directly into the unsealed penetrations.
How We Fixed It
We removed the tap handles and spindles so the penetrations could be accessed properly. Both penetrations were then dried using a blow dryer and cleaned thoroughly using Diggers Isopropyl spray.
Once the area was clean and dry, we applied Soudal T-Rex Crystal deep into both tap penetrations using a Milwaukee electric caulking gun. The nozzle was pushed in as far as possible and the product was applied until it came back out of the penetration, ensuring the void was properly filled. We then tooled the sealant flush around the tap penetrations using a Soudal caulking tool to achieve a neat finish against the tile face.
Because it is important to allow the T-Rex Crystal enough time to cure properly before reassembly and testing, we stepped away from the job and went for lunch in 1770 before returning later that afternoon.
While the sealant was curing, we removed the damaged skirting board on the adjacent hallway side.
Once back on site in Agnes Water, the sealant had fully cured. We then re-tested the shower by running water over the repaired area for five minutes. With the skirting removed on the opposite side, we used a torch to check whether any further water was tracking through the wall. There was no further leakage.
After confirming the repair had worked, we installed new skirting, applied Soudal No More Gaps Quick Dry, completed the paint touch-up, and reinstalled the taps. The client was extremely happy to have the issue identified and resolved in a timely manner.
Products Used
Diggers Isopropyl spray
Soudal T-Rex Crystal
Milwaukee electric caulking gun
Soudal caulking tool
Soudal No More Gaps Quick Dry
Why This Matters
This job is a good example of why bathroom leaks need to be investigated properly rather than guessed.
The visible damage was outside the shower, but the actual cause was inside the shower wall at the unsealed tap penetrations. A small missed sealing detail had allowed water to enter the wall cavity and cause damage where most people would not expect it.
It is also a reminder that even minor defects around shower fixtures can lead to larger moisture problems over time if not dealt with correctly.
At Big Bass Building Solutions, we carry out bathroom leak investigations, remedial waterproofing repairs, and renovation work across Agnes Water, 1770, and the wider Discovery Coast.
Need Help With a Shower Leak in Agnes Water or 1770
If you have swollen skirting, damp walls, signs of water ingress, or a leaking shower in Agnes Water, 1770, or the wider Discovery Coast, Big Bass Building Solutions can help identify the cause and carry out the right repair before the damage gets worse.