I'm a property manager and my company aquired a new condo about 9 months ago. Upon inspecting the unit today I noticed a line of black mold under this ledge in the shower.. The ledge is apparently a seam where the shower wall attaches to the lower portion of the stall/bathtub. This seam does not appear to be well sealed.. There is evidence of some caulking having been done at some point but it's deteriorated and in no way is it providing a watertight seal along this seam.. Some lengths of it have no visible caulking but a noticable gap between the pieces. The mold is also growing out of the overflow hole in the drain stopper and creeping from around the faucet fixture ..I am thinking the area surrounding the shower stall inside the walls is soaked.. Rotting and full of black mold.. I'm going to guess that caulking the seam and the fixtures and pretending I know nothing is not an option.. What are my options and how bad could this be? I do have a moisture meter that you stab into the drywall and also have a snake video camera thing... What do I do..I need some answers ideas and solutions before I approach the owners with this news... Please help!!

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    Having the mold tested for type might be an idea. There are thousands of types, but a few do have very negative health concerns. Being more of a commercial business, depending on type of mold might lead to big lawsuits if not taken care of the right way. Adding a bit of sealer and washing what you can see might not be good enough.
    – crip659
    Commented Nov 2, 2022 at 11:42

2 Answers 2


Pictures here would help, but I believe I am familiar with the type of tub/shower enclosure you are speaking of. The wall panels overlap the tub flange by about 2-3 inches. Some manufactures do not recommend caulking, as water intrusion is unlikely during normal use. So lack of caulk does not mean there is reason to expect a problem. The black mold may simply be the result of soap scum collecting in those areas providing the mold spores something to grow on. this is especially true if the unit was vacant and unused for months. (I have purchased homes with baths in this type of condition. Torn out showers and such to remodel and found no problem behind them.) That said; Your due diligence would dictate that you remove the trim from the control valve and use your camera snake to see what is behind that panel. If the result is negative for water leaks and mold issues, you have done what a reasonable person could be expected to do. If there are signs of mold or water then of course repairs and remediation are required. Good Luck


I agree that this seems to be a “moisture behind the enclosure” problem. I think the main question is what is the entry point of the water? Is it coming in high and running down? Is it coming in at the bottom and washing in and out like the tide when the shower is used? Is it a vertical seam leak? Is it a completely external leak, maybe coming from the roof (yea, that’s a long shot).

Your camera and moisture meter will help you find that answer. If it’s limited to a leak at the bottom, might be salvageable. Depends on the extent of the damage and your ability to access the area to clean up and repair. If it’s just surface mold, you can use a mild bleach solution to kill the mold, scrape it out and reseal the seam. I like to lay in paper towels and then soak them with the bleach solution using a spray bottle. That controls the bleach better and reduces splashing.

You might have some success in removing the two piece enclosure and reusing it. Depends on the condition and if it gets damaged in the removal. I’d get permission before moving forward on that plan, because the outcome (and cost) can vary.

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