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How to fix mould behind shower tiles?

Our bathroom was renovated nearly 10 years ago by a reputable builder. In the last six months I have noticed mould on the tiles in the shower only. It is not surface mould, but appears to be coming from behind. There is no real indication of mould in the grout. What could it be?

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EricL

Hello @tash_rainf

Welcome to the Bunnings Workshop community. It's sensational to have you join, and thanks for sharing your question about fixing mould behind your tiles.

If there is mould under the tiles, I'm afraid the only way to get to it is by removing the tiles. Theoretically the mould would have had to form behind the tile and travel through it to get to the top. Following this sequence of events, it's probable that moisture would have got in between the tiles and the waterproofing membrane.

I am surprised though that the mould is only appearing on the edge of your tiles and nowhere else. Is it possible that mould could have entered through the edge of the tile? But that would mean that a great amount of mould would have to grow on the edge to infest the interior of the tile.

I can only suggest thinking about replacing the tiles as I am unaware of a method or product that can reach the back of tile from the front.

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

If you need further assistance, please let us know.

Eric

Dave-1

Good Evening @tash_rainf

ohhhh 😕 and ugh at the same time.

Are you sure its mould and not a discolouration? And yeah I trust your view but my mind is hesitating 🙂 Mould being able to grow through the surface and come out of the glaze of a tile sounds like a pretty decent mould that would be able to appear all over the area. I wonder if its a faulty batch of tiles where the glaze is thinner on the edges of the tiles? Have you got any tiles with the mould in the middle and not the edge?

I dont know of any way to remove that 😕 And @EricL 's suggestion gets closer to havingto be done. 😕

Maybe you could take your photos to a tile place and ask if they have seen it before or if its a discoloration on the glaze?

Dave

tash_rainf

Thanks Eric. I agree it does seem odd that it’s only in the tile and not the grout also, which is why I’m worried it is worse than it looks 😕

tash_rainf

That’s an interesting suggestion @Dave-1 I will look into that too. There are no other tiles where it is in the middle. My main reason for thinking mould is because they are the tiles closest to the ground and shower head, so probably the wettest part of the shower.

Dave-1

Evening @tash_rainf

Thats making me head more and more to a faulty batch of tiles, especially with the heavier use lower tiles would get (not a hugely greater use lol but more with water pouring over them)

Dave

Nailbag

Hi @tash_rainf

Other than @Dave-1 ideas and @EricL my two best guess's are based on you mentioning the discolouration is in the wettest part of the shower.

1. A poor quality grout is holding moisture that over time is soaking in to the edges of a porous tile.

2. There is a waterproofing issue coming from the back of the tiles.

Whatever the cause, the tiles will most likely need to be replaced as the discolouration will not be remedied. The angle I would take would be to first contact a shower tile restoration company to have a look as they will be best experienced over any service to have seen the issue before as well as provide a solution. If water ingress has been the cause, they can seal the top surface and then if they don't, you could look at a tile paint option.

Regards, Nailbag

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