Water Under Marble Shower Floor Tile

by Ed Kowalewski
(Pooler, GA, USA)


Lysol 4 in 1 was used on our tumbled marble shower (this is dull not shiny marble) a few times. Recently we noticed in certain parts of the shower floor the grout is either discolored or wet, when the rest of the shower is completely dry. Due to marble being porous, is the water collecting under the grout caused by the Lysol? If so how do we fix this?


I wouldn't recommend using the Lysol cleaner, but I don't think it has anything to do with your grout being constantly wet in areas.

And it isn't because of the marble. Marble is actually not very porous although you read that bogus info quite often online because people are confused about staining vs. etching, but that's another matter.

The likely problem is either cracks or voids in the grout or a bad installation allowing water to collect beneath the tiles. Or it could just be that those areas are the lowest lying areas so all water will drain there and that will be the last place to dry out.

So, allow the shower to dry out for a few days. Note how fast the areas in question dry out. If they take 3 or 4 days to dry, then you have water under the tiles/grout. Carefully inspect all grout lines and repair those that need it.

If you continue to experience the problem then you'll probably have to rip out the floor and re-install it to solve the issue.

And don't seal it. That will only exacerbate the problem by trapping water. Stone needs to breath, especially in a wet environment.

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Is Water Under Carrara Marble Shower Floor?
by: Rob

Is there a way to determine if water/moisture is stuck under the marble tile?

I am not concerned about color change, only concerned about trapped water/moisture.

How can I tell if the marble has dried and or if water is under the tile?

==== Countertop Specialty comment:

Well, if it is indeed standing or slow-draining water under the tile then the tile would absorb it and saturate the tile.

A tile saturated with water will be darker than the surrounding tiles and/or a normal dry tile of the same color and tile batch.

The way to determine if water is under the tile is to give the water a chance to evaporate from the tile.

You do this by not using the shower for several days. Possibly not use it for a week or two.

It just depends on how much water may be trapped beneath and on your climate (hot and dry or humid).

If it is water trapped under the tile causing the darker color, then that darkness will lighten and eventually disappear as the water evaporates and the shower dries out completely.

You should be able to see this happening. Taking a photo (same angle with the same light) every day can help you determine if the dark stain from water is getting lighter.

If something else has caused the tile to darken (like oils or products staining from the surface into the tile) then it won't get lighter in color.

A second option... Is to cut the grout and remove a tile or two to see if standing water is underneath or not.

Of course, not much if any water should get underneath the tile, but the mortar bed and liner beneath the tile is supposed to be carefully sloped so any water that does get underneath can drain off.

But there could be various reasons that all the layers below the tile are not quite right and not functioning correctly.

Maybe the slope is off and it's not draining well in a certain area so the floor is holding water saturating the tile, etc.

Also, you need to carefully inspect all grout lines on the floor and any caulking around the floor/wall joint for cracks or voids that may let water in.

So, that's how you check... let the shower dry out completely or remove a few tiles and check underneath what the situation is.

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