Ceiling – How to permanently remedy a patch of mold on a ceiling from a water leak above

What this could be is that you have a slow leak from the floor above. Probably a water feed rather than a drain. Although it could be from the heating system if you have a water or steam system with radiators. When you turned the water on the house it started to drip, and the ceiling soaked it all up. Eventually the ceiling became saturated and started to drip onto the floor.

If you do have a slow leak then obviously you need to find the source. It's probably a leaky pipe joint, or maybe a loose compression fitting. The only way you're going to find it is to get access, as for how that completely depends on your house's construction. There may be a panel in front of the bath that can be removed, etc.

What you need to do is meticulously go through the whole bathroom above and look for any kind of access to pipes you see, and look for signs of dripping moisture, oxidation on the pipes, or hard water deposits. As it sounds like the whole ceiling needs to come down on the floor below do that first, then use that access to find your leak.

As for how to fix it if it's a compression fitting get out your wrench and have at it. If it's a solder joint or a bad pipe get a plumber in unless you have the tools and the experience. Good luck!

If there is mold on the basement ceiling, it is highly likely that there is mold growing behind the drywall where water has wicked up the bathroom walls -especially if this has been an ongoing, untreated problem. I personally would not try to save money at the risk of leaving mold growing in that area.

Mold can trigger a host of health problems, some very serious. I once met a woman who had a condition where she was debilitated by sensitivity to perfumes and artificial fragrances (contact or exposure could cause her to be be bed-ridden for months at a time. The weekend I had met her was the first time in three years that she had left her house (her home was a strictly controlled environment - air filters, hermetically sealed rooms, the whole nine yards. She explained that her condition was triggered due to living in a basement for about 8 months where mold was present in the ceiling (she didn't find out about the mold until after she came down with the health problem. I know this is an extreme example, but it is one example of what can happen if mold is left unabated.

Sorry about the verbose response, but take the repairs seriously and don't skimp out just to save time or money. Your long term health is worth the up-front cost of repairs.