Leak into Subfloor [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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11-18-2005, 03:18 PM
Hello friends. I recently tiled the floor of an upstairs bathroom and replaced the cabinets, sink, etc. It turned out great. The book and this forum have all been helpful.

I did not touch the bathtub or bath tile during this remodel. Well, as it happens, the tile in the shower developed a leak and the water pooled under the tub. I decided to replace the tub and tile. Demolition of the bath and tile is now complete.

Here is my question. The water that pooled under the tub leaked into the adjacent plywood subfloor. Construction is a 5/8" structural floor, 3/8" plywood, 1/4" Hardibacker Board screwed and mortared onto in the plywood, and tile on top of that. I assume it spread about 1 to 2 feet under the floor. The grout in that area is discolored, and this is probably due to the floor being wet underneath. Do I tear out two rows of 12" floor tile to dry it out? Or will it eventually dry on its own without problem? Will the grout discoloration clear up after it dries out?

Thanks for your thoughts,
Aurora, Colorado

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Dave Taylor
11-18-2005, 03:29 PM
Put a floor fan in this area and dry it out well... it will dry if yer leak is fixed. The grout will probably return to proper color and.... there is probably plenty of time to tear this out if drying don't work. It does not sound like any of the materials you mentioned will be badly affected by the wet.

Good luck.

11-18-2005, 04:34 PM
It has been drying for about a week now, and I still have the grout discoloration. I suppose that if the discoloration does not clear up after a few weeks, I could remove the grout from that area and regrout.

11-18-2005, 09:51 PM
Welcome, Mark. :)Construction is a 5/8" structural floor, 3/8" plywood, 1/4" Hardibacker Board screwed and mortared onto in the plywood, and tile on top of that. By "structural floor," do you mean plywood?

I would certainly want to get a good look at all that plywood to be sure it was not damaged by the water if it was wet for any length of time. Difficult to know what grade it might be or how wet it got. Can you get a good look at the edges at least? How 'bout from underneath?

The grout either will or will not return to it's previous color. But that's just a guess. :D

What color did it start life being?

My opinion; worth price charged.

11-18-2005, 10:07 PM
The structural wood floor is OSB as you find in many homes around here. The bathroom floor is well supported with no deflection. The subfloor is plywood as I said. Everything is screwed together tight. I cannot see the bottom of the floor, however, there is no evidence that the water soaked all the way through the 5/8" OSB. (peeking through an access hole I have).

Looking at the edge that met the bathtub, everthing seems to be holding together.


11-18-2005, 10:39 PM
I measured and the floor is 3/4" OSB. Using a mirror and flashlight, the water did not soak all the way through the OSB. There were a few small hairline cracks in the grout in the area where it became wet, but only noticable if you are close. Therefore, I imagine there was some swelling, but not too much. I inspected the edge of the plywood again... no separation.


11-18-2005, 11:05 PM
Hmmm. See can you find another place to measure that OSB, Mark, somewhere that has never been wet.

Here's the problem: OSB is good stuff so long as it stays dry. But when it gets wet, it swells pretty dramatically, and once it's done that it loses much of it's structural integrity and it never returns to its previous size and shape, even after drying. So if you find that it started life as 5/8ths OSB, but now it measures 3/4 inch (and perhaps pushed up the underlayment and substrate causing that grout cracking), you could have a problem that really wants attention.

To prevent possible confusion in further discussion, that OSB layer, the one attached to the joists, is the subfloor. The second layer of plywood can be called a second layer of subflooring or an underlayment layer. The Hardiboard is the tiling substrate in this case.

You're the onliest one here who can see what you've got, so you gotta decide if it's usable as is or not. I urge caution if you already see some cracking in the grout. Be a shame to go through all the work and expense to rebuild a shower and end up with a constant floor tile cracking problem in front of it. :shades:

What's the joist type and spacing under that floor?

My opinion; worth price charged.

11-19-2005, 12:07 AM
One fact I supplied was confusing... My earlier statement that the floor was 5/8" subfloor was incorrect. It is 3/4" through the entire house. Now... I'm not quite sure how to tell how wet it got. It never soaked through. I don't notice any deflection whatsoever. I'm on the fence as to whether or not to rip a few rows of tile out.

Either way. You gave me more to think about! :think:


John Bridge
11-20-2005, 01:15 PM
Hi Mark, :)

I doubt the grout will ever return to its original color. I think procrastination is the best approach right about now. I wouldn't tear anything up just yet. ;)