Thanks, Bill. I talked to my contractor this morning and he said: 1. He used silicone at the corners of the sheet rock. He also said the reason he doesn't like to use caulk at the corners is that even though it is supposed to be the same color as the grout, it really isn't, plus the caulk will crack if the building moves just like grout cracks. I asked him about grout behind the caulk and he said he recommends keeping the bathroom dry by using a squeegie/towel where needed, particularly along the top of the tub. The grout looks so nice I guess I'll wait to see if it cracks. It probably will as the roof needs more work and I guess I'll caulk at that time. 2 and 3. There isn't grout at the tub line. It just looks like it as the grout is the same color as the empty space. (That's what I get for looking at it at night.) 4. OK 5. Tub reglazing was put last on the schedule so that it wouldn't get damaged during the other stages. I am going to have them cover all of the walls up to the tile line, and the floor, with plastic.

I agree that it sounds like you need to rip out & start over, but for a temporary fix...Use a razor to remove the caulk. Spray down with Tilex or other bathroom cleaner made for mold/mildew. Bleach in this case is not a bad thing--you will need it to kill what is growing now or it will simply come right back. Follow the directions on the bottle to the 'T'. Once everything is nice & white again, rinse it down, squeegee the surfaces including the floor & allow the shower to dry at least 24 hours. Then recaulk with a silicone based caulk that is waterproof. Wait another 24 hours before using the shower. Sealing the grout may help. Another tip is to use a squeegee on the tile (both walls and floor) after every shower--standing water is the medium that allows the mold/mildew to grow. Leave the shower door/curtain open to allow the shower surfaces to fully dry after each shower. Good luck to you!!

It was sealed with Aqua Mix Professional Sealer's Choice Gold, recommended/provided by the slab dealer. It says provides up to 15years stain resistance. It says for all natural stone, does allow some vapor transmission. The old white "rotting" caulk is on all sides, under the showerhead/pipe wall, the side, and rear pony wall; they all get different amounts of water, and we squeegee the walls & tile floor clean each shower. The shower pan was custom built, with concrete sloped base per code, thick plastic liner (which passed leak test), mortar bed, marble tiles on top; the walls are solid slab pieces, over Hardibacker wallboard, with tar paper overlapping w/ the plastic liner, etc Another contractor removed most all of the old grout, sealed it with new pure transparent silicon caulk, last week.. and over the last week of use, one spot has started swelling/"rotting" again.

You must be certain of the source before you can fix it. Picture 1 is confusing,pictures 2 & 3 look normal and only need to be caulked between pan and wall. If you want to systematicly go about looking for the leak,tape clear plastic to top of wall all way around with duct tape. Let plastic hang to floor of pan and overlap for entry/exit. Only hole is where shower head come's through. Lift plastic and put hands behind to control facuet handles. Be sure 7 yo understands how to use shower and leave in place for 2 or 3 days while useing as usual. If no leak is observed,you know caulk is the answer. If it leaks, rempve drain cover,clean up inside of pipe and measure inside diameter of drain pipe. Buy an air inflatable test ball,half inch female pipe thread cap,teflon tape or pipe dope and a device that replaces airator on basin facuet and converts to garden hose threads. If you can bring a garden hose from somewhere else you don't need to mess with basin facuet. Insert and inflate test ball then fill one forth to half depth of shower pan with hose. Have heaviest person in house walk around in pan to see if it leaks. You might also leave water stand for a couple of hours. If that doesn't leak you just eleminated drain as source of leak. Remove shower head, cap pipe then turn on hot and cold and watch for leak in usual place. After five minutes,close each handle 1/2 turn,wait five minutes watching for leak. Continue closing by half turns and pausing until both handles are completly closed. No leak eliminates packings and riser. Report back.