Hello,

I've just noticed a fairly large water mark with mold in the center located on the ceiling of a downstairs closet - I believe the closet sits below an upstairs shower.

I'm a new home owner and would appreciate your advice on what sort of questions I need to ask a plumber to resolve this problem. I'm wondering also, if there is mold appearing on the ceiling - how extensive might I expect the damage?

Thank you very much for your guidance.

If there is mold on the ceiling, I would guess the problem/damage is pretty bad. I would call a plumber and ask them about it, I would guess they'd probably tear out the old bathroom fixture/fixtures and fix the pipes/plumbing and replace them. I'm not an expert by any means but you definitely should have it looked at by a professional as structural damage to your house is a bad bad thing.

Tear out the entire closet ceiling, it can't be saved. Once inside you should be able to see where the leak is located, you may have to turn on the shower if it's the drain or shower head. If the leak is active without turning on the shower it is likely a supply line or mixing valve. If you have done this stuff before then go for it, if not call a licensed plumber but you can do the clean up. The mold must be killed, buy a mildewcide with at least 2.4% bleach, I think the chemical name is sodium hydroxide. This is just an ad but it may help Household Mold: Removing Mold

Just a heads up - the active ingredient in bleach is sodium hypochlorite. Although sodium hydroxide would likely kill the mold as well!

First check the caulking around the tub and grouting of tile for cracks and any break in integrity after repair and resealing of said items check your fixtures for leaks once all this is done go down to the closet cut away the moldy
Sheetrock take a flashlight with the shower on toilet flushing and the sink running look for leak and pinpoint by elimination also I have found the tub diverter valve leaking on occasion behind the escuetion plate especially if the valve has a leak and runs constantly make shure you get that water everywhere in that tub it helps if you have someone there to help you preferably with a cell only other place is the tub drain and toilet wax ring wich all should be seen by pinpoint of elimination after you find and repair leak prepare your sheetrock patch screw it down if no stud in area
Measure hole cut sheet rock about 2 inches wider around hole measure and mark sheet rock on overcut piece and carfully score back of sheetrock to correct measurements now stripaway scored sheetrock and paper I like to use a hammer and smash the scored 2 inch trim rock away carefully
Leaving the front 2inch paper in tact now you have the perfect patch screw down a two bi fore in center and screw sheet rock to screwed two bi fore
Make shure you put two bi fore in the ceiling and then atach patch mud it up after it dries spray some popcorn for texture dry it and paint it or just paint it witchever type you have and your done!