First, could it simply be that everything was installed properly and is performing well, but it's just residual moisture on the shower head wall that is trickling down the the face of the tiled wall over time and wetting the joint?

Inspect that wall/floor grout joint. Is the grout flush with the face of the tile, or the grout is it recessed into the joint at all? If the grout in the joint is recessed, it could be holding water.

Take a straight edge and place it on the shower floor tile, in a line from the floor drain to the floor/wall joint in question. Is the slope of the floor uniform and consistent all the way to the wall, or does it flatten out at the wall? If the floor flattens out by the wall, it could be slow draining.

If all that looks good and you want to check the plumbing:

You can cap the shower head arm. Get a 1/2" threaded cap similar to this:

1) Let the grout dry.

2) Leave the shower arm in the wall, but unthread your shower head from the arm.

3) Remove the wall escutcheon from the shower arm.

4) Just crack open the shower head valve a bit so water trickles out of the arm, then turn the valve off. The goal is to fill the shower head supply tubing with water versus air. Doesn't have to be perfect.

5) Using a few wraps of teflon tape or pipe dope, thread the 1/2" cap on the shower arm.

Now open the shower valve. Leave it on for several minutes. If you can shine a light into the shower arm wall hole you can do a visual inspection for any leaking in the wall at the shower arm fitting. If you have a Q-tip and it'll fit in the hole, you can poke that around. See if it comes out damp.

If no water shows up anywhere after a reasonable amount of time, it's a reasonable indication that the shower head supply is all nice and tight behind the wall.

If the shower arm union was dry but water indicated at the grout line, then it could indicate a leak somewhere behind the wall. The supply valve outlet, the diverter, any of the unions, etc.

Repeat the procedure for the hand held.

Thanks for your quick response.

I showered late morning yesterday, around 11-11:30 and at 10:15pm the right half of the wall/floor seam was still damp. A small amount of water even pulled away from the grout and remained on my finger after I touched it. I also noticed a hairline crack in that corner moving toward the center of the wall (toward the shower head) and I could scratch the grout away with my fingernail.

I spoke with the installer earlier this morning and he'll be stopping by this afternoon to take a look. He didn't seem too surprised or upset and mentioned that settling could cause the little crack and subsequent remaining moisture. He plans to remove the soft grout and caulk with matching sanded caulk. I imagine if there is too much soft grout, he'll remove/replace it and then caulk later.

I also read about testing the plumbing connections by capping off the shower arm, but I was thinking yesterday, if the plumbing is behind layers of 1/2" cement backer board, paint on waterproofing (black waterproofing paint completely covers 1/2" backer board), the pan liner, and tile, how would water get to the inside of the shower pan and wick through the grout? Also, there is a lower level bedroom located directly below the shower... wouldn't evidence of a leak (dark spot) already show on the ceiling?

Anyway, Rich (tile installer) said he needed the area dry to do what he plans to do today so we'll use another shower today and for the next few days. If the repair he makes doesn't solve the problem, then I'll do the plumbing test. I don't have the cap on hand, otherwise I'd try it before he arrives today...

Thanks,
SBerg59

"if the plumbing is behind layers of 1/2" cement backer board, paint on waterproofing (black waterproofing paint completely covers 1/2" backer board), the pan liner, and tile, how would water get to the inside of the shower pan and wick through the grout?"

When I posted I didn't know how your shower was constructed. But if you have a topical waterproofing on your cement board and a pan liner on the floor, the pan liner membrane goes down and gets lapped up the walls 8" to 10" and gets stapled to the studs. The cement board on the walls goes over the pan liner.

If there was a leak behind the wall, it could spray on the back of the cement board. It could run down the cement board and go between the cement board and the pan liner, wetting the mud in the floor.

I'm not saying that is what's happening. But it's an option. I've seen it before.

And you are correct, a water leak behind the wall could show itself in a ceiling below.

With the "new news" that the grout is cracked, yes, water could be getting into that crack, thus the slow drying at that joint.

In lightweight shower construction, changes in plane (wall-to-wall and wall-to-floor) should be caulked instead of grouted. The surfaces can move independently of one another. Caulk will flex with the movement, grout can crack.

Also, if he used a "pan liner", it should have been set on sloped deck mud. Not flat on the subfloor, with sloped mud on top of the flat liner.

The flat liner can cause moisture that gets under the tile (through your cracked grout for example) to pond. It can show as damp grout lines that are slow to dry.

If the liner was sloped as required by code (which yours may be), the moisture will hit the sloped liner and flow towards the drain.

If he used a topical membrane on the walls and on the floor instead of a pan liner on the floor, then all of the above is pretty much non-applicable. With a topical membrane on all shower surfaces, it's probably just latent water running down the shower head wall, or the crack in the grout storing water and being slow to dry.

Thanks again mongoct for your thorough response. Rich was here yesterday afternoon and pretty much said the same thing. He used matching sanded caulk to seal the entire wall/floor perimeter and said to wait a few days before using the shower to let it thoroughly dry. I wish he'd also caulked the wall/wall joints... but I can always do that another time or maybe I'll just do it today and get it done.

I think this will address the issue as I'm confident that everything else on his end was done properly (mud preslope, liner, pan slope, topical waterproofing... (yes, he did both liner and topical) and it's unlikely its a plumbing leak.

Thanks again for your detailed information, it is greatly appreciate by me and I'm sure others on this forum.

SBerg

We had our guest bathroom shower remodeled one year ago, 2 weeks ago my wife noted shower floor grout wet around the edges, with some spots dry. Had the guy who remodeled the shower come look at it. He opened the wall to adjacent closet in the next room to assess the shower pipes and no leaks found. He also checked the water meter to see if the arrow was turning indicating a leak, but it was not moving. He didn't know why the grout was wet. I then had the plumber who re did all the plumbing in the house a few years ago and he checked and found no leak, checked water meter to confirm. He believed that small cracks in the grout may have water leaking through it. I have applied a paper towel all around the edges and have noted that it absorbs water. a few days later I have noted that there are now some dry spots but tissue is still absorbing water in some areas along the edges. What is going on?

"Black waterproofing paint".....what would the be..I've seen red, green, and blue used in showers, but not black. If the "black paint" was something like the elastomeric paints used to seal roofs and basements and there is insulation behind it with a vapor barrier could vapor be being trapped?