Is this mold? (walk in shower)


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Old 04-26-21, 08:27 PM
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Is this mold? (walk in shower)

I'm thinking that I may have black mold behind the procelain tile in our walk in shower. The grout and silicone are still good (no visible cracks or leaks) and looks clean and white all over. However, I see this "shadow" on the bottom row of tiles, and a couple tiles have ring spots (see pictures).

Note - the shadow and ring spots are "inside" the tile, and cannot be cleaned away with bleach or vineager no matter how many times I try.

What do you think? Should I destroy a clean looking shower due to this shadow? Is it normal for mold to darken tile from the inside like this?

 
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Old 04-27-21, 02:25 AM
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Mold can not grow inside tile, it requires a food source and there is nothing in tile. If it were behind the tile it still would not be visible through the tile.

It would appear to be nothing more than a discoloration of the tiles.

Now for the most puzzling aspect of your shower, is that a tub spout just off the floor? If so why?
 
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Old 04-27-21, 04:56 AM
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Same question. Maybe just for a foot wash? Not a bad idea I guess.
 
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Old 04-27-21, 07:26 AM
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Plus it has a shower diverter so how does that work in a shower?
 
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Old 04-27-21, 10:22 AM
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I think it is called a "toe-tester" to check the temp before starting the shower. All the builders around here install them. I've never used it as intended.

As for the spots, what do you mean by "discoloration"? These spots are all on the bottom row of tiles and are multiplying with time. So something is going on. I see another thread lower on the first page here with similar spots (also all on the lower row of tiles).
 
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Old 04-27-21, 03:21 PM
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Are those tiles glazed? Or do they have a rough surface? If they are discoloring then something is getting into the clay.
 
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Old 04-27-21, 11:44 PM
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Looks to be glazed but not super glossy. It is also very thin (~3mm).
 
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Old 04-29-21, 06:43 AM
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"Toe-tester", eh? I always carry around a hand which is handy for checking the temp before climbing in.

Anyway, since the discoloration seems to all be at or below the level of said toe-tester, maybe the connection is leaking behind the wall and moisture is somehow causing the tiles to darken? Tub spout could be removed and an inspection camera inserted to take a look around.
 
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Old 04-29-21, 02:46 PM
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Well, I found an extra shower tile in the basement and it is ceramic (not porcelain) and about 3mm thick. The backside (unglazed) absorbs water as good as a sponge (actually really incredible) and creates a shadow effect seen from the front glaze. I submerged only 1 inch of the tile into water and within an hour it had wicked up water 5 inches above the water line.

No doubt now that my bottom row of tiles is wet on the inside, and probably has been for years. I suspect the builder installed the drywall or whatever too close to the shower bed and water is wicking up the walls and wetting the back of the ceramic. Surprised the tiles haven't fallen off the wall. The grout looks intact and solid all over.

I managed to get a look at the subfloor beneath the shower via the floow below (pot light holes). Zero evidence of water damage anywhere. Next, I will cut a hole in the drywall on the opposite wall of the shower to see the state of things.........
 
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Old 04-29-21, 03:05 PM
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Most likely they used just plain wallboard, not even green board.
 
 

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