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How to fix hole in wall behind toilet?

During my bathroom renovations, there were many issues with the toilet installation. Initially a different style toilet was put in that wouldn’t get in the way of the wall tiles. Unfortunately it was put in wrong and when this was being fixed (with a new type of toilet), the plumber told me most people cut the tiles to fit the toilet flush against the wall. And in my naivety I said sure if that’s what normally happens you can! And was said that it would just need some caulking done.

ive now been left with a gaping hole behind the toilet, and a crooked cut tile on one side.

how can I patch this part of the wall? It currently has backing rod to fill the space but it will leave me with too wide caulking on top.

do I need to get new plaster in there? It also means the waterproofing membrane has been removed from that section, is this really bad? It’s one big bathroom, but shower is fully enclosed so I think it makes this section low risk?

please help me fix the hole in my wall!

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MitchellMc

Welcome to the Bunnings Workshop community @megmeg81. It's terrific to have you join us, and many thanks for your question about fixing a toilet installation.

Most of the issues you’re facing stem from the tile being cut out to allow the toilet to sit flush with the plasterboard, but the toilet doesn’t actually appear to have been pushed back properly. It’s still mostly sitting in front of the tiles, only slightly rebated into them. I suspect the wall isn’t perfectly straight, and the top of the toilet has hit the wall first, preventing the base from sitting in tight.

If this is a recent installation, I’d really recommend having the plumber return to finish the job properly. The wall behind the toilet should have been cut neatly and adjusted before the toilet was fixed in place.

As for the waterproofing, if they cut into that section of wall and removed any of the membrane, it should have been reinstated, even if it's outside the shower zone. If they’ve also cut through the wallboard and left the internal cavity exposed, that’s a definite concern, especially long-term with any potential water splashes or humidity.

Honestly, this isn’t just a cosmetic issue. The wall needs to be repaired and re-waterproofed, then the toilet properly installed so it sits flush with the wall. Only then should it be caulked for a clean finish. I’d be pushing the original installer to correct this, or if that’s not an option, you might need to get another professional in to fix what’s been done.

Please let me know if you have any questions.

Mitchell

megmeg81

Thanks so much Mitchell, this confirms it’s a bigger issue than it was explained to me initially… it was completed September 2024 and was the fix to the initially poorly installed toilet.

do you know if this is now too long to have the initial plumber return and rectify the issue or be under warranty/liability insurance?

MitchellMc

It would be best to reach out to the installer to discuss the issue, @megmeg81. You could ask them whether they compromised the waterproofing and if the installation is compliant. They might be able to advise on whether the waterproofing was breached and whether they could return to add silicone to the gap.

The other option is to have another professional provide a quote for fixing the issues. They'll be able to inspect it and let you know if the membrane was compromised.

Mitchell

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