We did a bathroom remodel which included new tile in the shower. Walls and floor. We have run a bead of caulking where the shower wall meets the floor.

The caulking appears to dry at first but after a few days it forms bubbles in places and begins to break down. It never really drys.

We have replaced the caulking several times all with the same result.

We have talked with the tile store and then with the manufacturer of the caulking. The caulking manufacturer told us the problem is that the mortar behind the tile on the walls has never completely dried. Therefore there is moisture behind the walls. The moisture is preventing the caulking from drying.

It has been 18 months since the remodel. 2 months ago we removed the caulking and decided to let the shower sit unused and un-caulked to allow the tile mortar to completely dry. To test it we have stuffed some tissue in the crack where the wall meets the floor. We leave it there for a day or so and pull it out. It does come out with some some moisture on it. Not soaked by any means but some moisture.

Does anyone have any ideas how we resolve this problem? Have you ever heard of this happening? How can it possibly take this long to dry? It has been 18 months.

I know it might sound strange for this to occur even 18 months later, but it can. There's quite a few very common mistakes made when showers are constructed that will make this a recurring problem.

First, the shower pan...

Most showers pans are done wrong. The plumber or contractor often places the shower liner on the subfoor, followed by the sloped mud bed on which the tile is set. Shower water goes through the grout and thinset, into the mud bed an hits the liner. WHat should happen next is that the water then gets drained out through weep holes that are below the mud bed at ring that clamps down between the liner and drain. This is so the mud bed will dry out between usage. When the liner is placed flat on the floor, there is no sloped drainage plane to direct that water to the weep holes. It should be a sloped bed, then liner, then the setting bed of mortar.

When the bed is sloped but still does not dry out, the cause is faiure to protect the weep holes from being clogged. Pea gravel, crushed tile, etc, placed around the drain collar prevents the weep holes from getting packed and clogged with mud.

In either case, the cement board walls are placed into the setting bed of mud, even though they are kept up from the bottom of the liner, the water collected in the pan will wick up the cement board walls from the constantly saturated pan. Now you not only have a constantly saturated pan, but you also have continuously wet walls along the bottom of the shower. Even worst is when mastic (or premixed thinset from a bucket) was used to set the walls. Mastic can potentially never dry all the way once the installation is grouted and wicking water behind the tile and water entering from the shower spray through the grout lines will make it all the more problematic and furthering the issue of moisture behind the continually failing caulk.

I'd bet you have a combination of the listed issues and would not be surprised if all of them were contributing.

Short of tearing it all out, I'd suggest removing the drain grate and run a dehumidifier in the shower stall for 3 or 4 days, sticking the dehumidifier drain hose down the shower drain.

After several days of mechanically forcing the removal of the moisture, try to recaulk. Tec specialty is one of the leading tile installation products manufacturers. They make a 100% silicone caulk in colors to match their grouts as well as clear. It can be used in swimming pools when allowed 14 days of cure time, so it should not be affected by constant water if allowed to properly cure. They probably have a color close enough to match whatever existing grout color was used. Call local tile stores and see who carries it. Lowe's carries some tec caulks but not the silicones.

Do you have another bath you could use, this could take a while.

Other than tear out and redoing it correctly, this is probably your best option

If you have stopped using the shower, removed the caulk and still find moisture inside the wall it may be time to start looking for a leaking pipe. What brand of caulk did you use and have you looked to ee a production date on it?

I thought for a moment about that, but a leaking pipe would probably be quite noticeable from a mold or mildew stain elsewhere. But, worth opening the access panel or escutcheon plate an taking a peek.

I have repaired some leaks that were only a drop an hour, these are the hardest to find because the draming can absorb and evaporate that much water for up to months if not a year. Yes, open the escutheon plate or access door and have a good flashlight handy.

Try drying joint with blow dryer and after its reasonbly dry apply a primer to lock in moisture try vulkem 171 urethane primer then caulk with mildew resistant silicone.

Sealing the joint may be very important but finding the leak is high priority if it is a pipe or drain leak.

Have u got adequate ventilation
? Showers every day produce steam as u know and steam settles as water