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  1. #1
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    Default What to do about a damp spot on 100-year old plaster ceiling?

    Hi Folks! Here's my situation. This February, I noticed some bubbling/peeling paint on my ceiling; at that time, I sc****d it all off to reveal a damp spot. The damp spot was approximately 3 feet wide starting from the outer wall, then it narrowed (funneled out) from that point to about a one foot. Now, as to what caused it? We had a tough winter. There was a significant ice damn on the roof in that area, and the gutters were NOT cleaned out. Another possibility, directly under the damp footprint above the ceiling is a radiator. We found out that the radiator's valve was not working properly and the packing nut was also loose. That radiator was super hot and hissing continuously throughout the cold months. When I say it was super hot, I do mean SUPER HOT...steamy, hissing, lots of knocking. Add to that, the room above the damp spot is a bathroom -- so, there is the possibility of plumbing issues to take into account. Anyway, it is now June, and the weather has finally started to warm up. The damp spot has not increased in size at all, the edge of the perimeter has turned dark/brown (not mold) and appears to be drying; however, most of the effected area is cold to the touch and still feels damp. In fact, I have been periodically scraping off white powder/crystals that are appearing on the spot (I heard this was common with old plaster when wet). There is no water dripping and the ceiling does not feel "soft" as it would if it were saturated with water. I took care of the gutter problem and was just waiting for the spot to dry before fixing it...but it has been over 3 months now! Like I said, no water dripping, ceiling is cold to the touch, feels damp...area has not increased in size. Should I just continue to wait this out? Could there be some other problem? If it were a plumbing leak of some sort, wouldn't the situation be getting worse with water eventually dripping from my ceiling by now? I'm kind of stuck on what to do next...any suggestions? It's a 100-year old ceiling, and I would hate to rip any of it up if I don't have to.

  2. #2
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    Default Re: What to do about a damp spot on 100-year old plaster ceiling?

    Tightly tape a piece of plastic over a 1' square area of the "wet" spot and leave it over night. When you remove the plastic, if there is condensation, then the spot is still wet, you still have an issue somewhere, and you will need to figure it out before repairs can be made to the ceiling. If there is no condensation, then paint your ceiling.

    The white crystalline substance is likely efflorescence, the salts in the plaster get washed out with the moisture. When the ceiling is dry, efflorescence should not form.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  3. #3
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    Default Re: What to do about a damp spot on 100-year old plaster ceiling?

    Quote Originally Posted by A. Spruce View Post
    Tightly tape a piece of plastic over a 1' square area of the "wet" spot and leave it over night. When you remove the plastic, if there is condensation, then the spot is still wet, you still have an issue somewhere, and you will need to figure it out before repairs can be made to the ceiling. If there is no condensation, then paint your ceiling.

    The white crystalline substance is likely efflorescence, the salts in the plaster get washed out with the moisture. When the ceiling is dry, efflorescence should not form.
    I'll do that, Thanks! I am a bit concerned that the ceiling still feels cold and damp after 3 months already. The only thing is that the damp spot has not grown -- but it still feels cold and damp. Is it normal that a plaster ceiling could be damp for months before drying out? I was thinking of drilling a couple of pilot holes into the ceiling to see if there was any standing water up there...then again, nothing is dripping and the ceiling is nowhere near soggy or soft -- just cold and damp.

  4. #4
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    Default Re: What to do about a damp spot on 100-year old plaster ceiling?

    Quote Originally Posted by hockeyp21 View Post
    I'll do that, Thanks! I am a bit concerned that the ceiling still feels cold and damp after 3 months already. The only thing is that the damp spot has not grown -- but it still feels cold and damp. Is it normal that a plaster ceiling could be damp for months before drying out? I was thinking of drilling a couple of pilot holes into the ceiling to see if there was any standing water up there...then again, nothing is dripping and the ceiling is nowhere near soggy or soft -- just cold and damp.
    Plaster, as a general rule, tends to feel cool/wet to the touch just as a matter of thermal dynamics. Can it still be wet, yes. Can it be dry but still feel cool, absolutely. The only way to know for sure is to either buy, borrow, rent, or steal a moisture meter, or tape plastic over an area and see if there is condensation. If it's dry, then hopefully the repairs you've made fixed the issue. If it's still damp, then obviously there is a problem still at hand.

    Drilling holes isn't going to accomplish anything. Plaster is porous, which is to say, it will wick moisture. If you've got an active leak to the point that you'd get running water out of a drilled hole, then the plaster would be weeping the water via gravity and you'd have drips/leaks/staining on the interior side. No, drilling a hole isn't going to prove anything, UNLESS there is standing water, which would already be apparent.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  5. #5
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    Jun 2014
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    Default Re: What to do about a damp spot on 100-year old plaster ceiling?

    Just a quick update. I taped the plastic to the ceiling and left it for 2 days -- no condensation on either side of it. I also went out and purchased a cheap moisture meter from Home Depot (really cheap, so I don't have too much confidence in it -- it seems to register/light up on cold surfaces that are not wet!) Anyway, the meter indicated moisture in the suspected ceiling spot (nowhere else). I went to the bathroom directly above, and decided to give it a try on the floor...well, it did give some readings right where the radiator was. As I said before, I had a plumber come over and he told me that the packing nut was loose -- he tightened that and replaced the valve as well. It could be just a coincidence that the readings below and above are directly around the radiator (after all, it is a bathroom and there are waste lines, supply lines running through the floor) -- but, since I had steam issues with that radiator over the winter, I'm inclined to bet on that as the problem. I think I will monitor this over the summer and wait to see if it dries out further. One more lingering question on my mind though was that I am constantly having backup issues with the bathroom sink, and have used Liquid Plumber a number of times on those PVC drain pipes -- I'm loosing sleep over the possibility that maybe I did some harm there -- despite the product label saying it was safe to use on all PVC. What about the glue that holds the damn PVC pipes together? Anyway, I'm going to wait it out for the summer. Thoughts? And THX!
    Last edited by hockeyp21; 06-09-2014 at 02:16 PM.

  6. #6
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    Default Re: What to do about a damp spot on 100-year old plaster ceiling?

    That is the problem with cheap tools, you can't trust their accuracy. If you think cold is triggering the meter, then warm up the area. Use a hair dryer next to the test spot so that you are not "drying" the test spot.

    You are also correct, a bathroom floor has a lot of pipes in it that could equally be the culprit, if indeed you have a leak.

    As to your sink back-up problem, usually, with a bathroom sink, it is a hair clog where the stopper lever penetrates the back of the drain to lift the drain stopper. Hair gets wrapped around the lever, grows slime, chokes off the drain. The fix here is to remove the actuator rod and lift out the stopper, usually the clog will stay attached to the stopper stem, if not, reach down into the drain with an old toothbrush or other implement that you will be able to grab the clog with, and pull it out. Your other choice is to disassemble the trap arm, but this can be risky, it could induce leaks, which is why fishing from the top is the best way to start.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  7. #7
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    Default Re: What to do about a damp spot on 100-year old plaster ceiling?

    Thanks, Spruce! One more question for you. I am assuming that I am also dealing with wet insulation -- which may cause the drying out process to take even longer?? If I set up a de-humidifier, would that help accelerate the drying out process? Should I even bother? I am in no rush and can wait the whole summer if necessary before taking the next step ... whatever that may be.

  8. #8
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    Default Re: What to do about a damp spot on 100-year old plaster ceiling?

    To be honest, we're not even sure you've got a leak.

    It is unlikely that there is insulation in the ceiling/floor cavity, so don't worry about that. If the moisture persists, then you could get black mold or dryrot, which means dealing with the problem sooner than later would be a good thing.

    What is the flooring in the bathroom?
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  9. #9
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    Default Re: What to do about a damp spot on 100-year old plaster ceiling?

    it's a tile floor over plywood. Unfortunately, there is no easy access. I would have to tear something up to get at it one way or the other. For some reason, I don't think there is a plumbing leak...I would have thought I would have seen water by now dripping from somewhere after all this time. This is why my thinking is to just wait it out and see, monitoring the ceiling over the summer to see which direction it is going... I suspect that if there is indeed a leak, the situation would get worse (increased in the area of the damp spot, etc.).

  10. #10
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    Default Re: What to do about a damp spot on 100-year old plaster ceiling?

    Quote Originally Posted by hockeyp21 View Post
    it's a tile floor over plywood. Unfortunately, there is no easy access. I would have to tear something up to get at it one way or the other. For some reason, I don't think there is a plumbing leak...I would have thought I would have seen water by now dripping from somewhere after all this time. This is why my thinking is to just wait it out and see, monitoring the ceiling over the summer to see which direction it is going... I suspect that if there is indeed a leak, the situation would get worse (increased in the area of the damp spot, etc.).
    I placed a call to some "Leak Detector" spe******ts in the area. *** -- $450 for 2hrs to find the leak? Apparently, they have some specialized equipment that will pin point a leak -- if there even is a leak!

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