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How to deal with high moisture reading?

Hi everyone! I’m hoping to get some advice about a long-standing moisture issue in my home. For years, I’ve noticed high moisture readings on a section of the plaster wall outside my bathroom. I raised this with my builder multiple times, but they couldn’t find any issues.
I eventually lodged a complaint with Fair Trading, and their inspector confirmed the high moisture reading, leading to a rectification order. However, my builder conducted their own investigation and claimed the reading was a “false alarm” caused by a treated skirting board used during an earlier repair. While they’ve dismissed the issue, I’m still skeptical.
Recently, when the builder repaired the plaster wall, they cut a larger hole, revealing what looks like a damp stain at the bottom of the interior wall (see photo). I touched the area and noticed significant dampness, especially in the corner. The builder insists this is normal, but I’m not convinced.
Has anyone dealt with similar issues or have expertise in this area? I’d really appreciate any insights or recommendations for trusted professionals who could assess this. Thanks in advance!

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EricL

Hello @SKC

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about the moisture in your wall.

It is difficult to make a diagnosis in regards to the condition of your wall. I propose thinking about engaging the services of a leak detection specialist and have them scan the area to see if there are any plumbing leaks occurring in that spot.

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you have any other questions we can help with, please let us know.

Eric

Dave-1

Good Evening @SKC

As the builder has recieved a "rectify work" instruction from the department of fair trading, I am presuming that they have fixed the problem, If they havnt done so to your satisfaction then I would return to the department of Fair Trading and let them know as a first step.

There should be no dampness inside a wall cavity, however they had cut the wall cavity to repair the issue exposing more of the moisture, so obviously there was moisture there before the rectification order was issued. If the repaired it all then no issue, if they didnt repair it and the wall fails a moisture check again then as before, back to the fair trading department. Its a pain in the neck but they are also the steps I would be following if I had the same issue.

Dave

SKC

I’d like to clarify the situation. After the rectification order was issued, my builder cut a small hole to access the issue and claimed that the high moisture reading was caused by the presence of a treated timber skirting board, which had been used to support previous gyprock repairs—rather than by a leak or water ingress.

Today, they came to remove the treated skirting board and extended the hole to the nearest stud. As a result, the bottom area—upon inspection—was found to be damp to the touch.

Based on our experience in previous years, our builder tends to use a very basic method for testing and often concludes that there is no issue. However, despite their findings, we continued to receive high moisture readings from our termite inspector.

Now, with only two weeks left before the rectification order is due, I’m concerned that the builder might once again attempt to cover up or hide the issue instead of properly resolving it. I’m not sure what steps to take next and would really appreciate some guidance on how to proceed.

Dave-1

Good Evening @SKC

Thank you for supplying more infor and timeline. I would still be contacting the Department of Fair Trading with your concerns as a first stop. They will be able to tell you the next step that is needed or will be checked. It also removes the builder from the equation (as in what he thinks is right compared to what is actually right) I would ask what the accepted outcome should be from the department of Fair Trading and what happens if the issue returns.

Does the rectification order supply any instructions on how the repair will take place?

And one last question, Is it in Aus or NZ? (Changes some things as I am not familure with NZ department of fair trading.)

Dave

SKC

Thank you for your reply.

We are located in NSW.

When the Fair Trading inspector visited, we got the impression that they were acting as a neutral party, which we understand. However, we were also told that he cannot advise or question the builder about what they’re doing—that only if we’re still not satisfied after the due date, then he will come back to inspect again.

The problem is, we don’t have any technical knowledge, so we’re unsure how we’re supposed to determine whether we are satisfied or not. We’re worried the builder might just cover up the issue (cause we have no knowledge about the issue) and that we’ll be left in the same situation after the deadline has passed.

Nailbag

Hi @SKC

I can 100% confirm that there is nothing "Normal" in finding moisture within any internal walls especially ones behind bathrooms. In fact that sends alarm bells ringing as it's an indication that the waterproofing is failing in some form. It could be something as basic as water ingress behind fittings that haven't been siliconed, to complete waterproofing failure in some or multiple areas.

If fair trading alone doesn't have the power to enforce the builder to make good, then I'm with @EricL in getting a "Certified Leak Detection" company to use their high-end scanning equipment to locate the source/s and report their findings. This information combined with those from fair trading confirms cause and result.

I would then take the information to both the building authority he's under and your building insurance company. This is the compulsory 7 year building insurance the builder must supply.

Keep the pressure on, because what he's avoiding is a potential full bathroom redo.

Here are a couple of useful links

HBCF NSW Gov

NSW Fair Trading Insurance

Nailbag

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