I have a ~2x3 foot water stain in my living room ceiling, I think because my toddler was forcing water behind the bathtub faucet. If there's insulation in the ceiling, then it should be removed. If there's no insulation, then I could just repaint. Of course if the source of the problem is a plumbing issue, then the question of insulation is moot.

Is there a way to find out without cutting? I saw somewhere that I could use an IR thermometer, but I'm not sure how that would work.

For what it's worth, the house was built in 1999 and is in the Mystic, Connecticut area where winter temperatures tend to stay in the range of 10-20 °F at the coldest.

[update] I asked the former owner. I didn't expect him to have info, but he did! He said that there was a bathtub related overflow from the owner before him which left a stain about the same area when he bought the house. That owner had just left it to dry, and that would have been before 2008-2009. So I assume that if they were able to let it dry out, then we could get away with that, too. That said, the next question is how many times can you spill water on sheetrock before it needs to be replaced... but that wasn't my question for this post. :-) Thanks! I'm not sure what I'll do... This is already the 2nd water damage issue of the year, and I'm not sure I feel like shelling out another chunk of money if I don't need to (i.e., what if a kid dumps water again next year). I did buy a blower fan so I'll try to dry it out completely and see if it stays dry.

  • Even if you have insulation, it will dry as long as it doesn't keep getting wet. That is a relatively small area and given you are keeping your house at around 70F this would dry out in a week or two max, no time to do any serious damage.
    – DMoore
    Dec 2, 2016 at 5:42

1 Answer 1


Interior walls aren't typically insulated. But to be sure you could just drill a small hole (make sure you're not on a stud) and if there is insulation it should come out on the drill bit. But be very cautious if there is plumbing in the area, you don't want to pierce a water line or drain pipe. Other than that, this won't hurt anything since the ceiling is already water damaged. Just putty over the hole before you repaint.

Though, if there is significant water damage you should probably replace the section of ceiling anyway as it may be weakened and/or also have mold growing on it.

  • How would I know if there was plumbing? Could I just drill really slowly and stop if I feel resistance? Or push a nail through first to make sure there's clearance and then drill to pull down insulation?
    – amos
    Dec 1, 2016 at 19:36
  • I'm not a professional, but since the tub is nearby you should be able to visualize where the plumbing is and which way it's running. If there's a chance it's near the water damage, then you'll want to pick a spot to drill least likely to encounter the plumbing and do a test, the nail idea should work. Instead of using the drill bit to try to pull out some insulation you could instead use a small piece of wire or a screw, or even a needle nose plier to see what's there.
    – Preston S
    Dec 1, 2016 at 19:53
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    Some stud sensors will tell you if plumbing/electrical (almost more of a concern) is there.
    – Joe
    Dec 1, 2016 at 19:59
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    You will notice a remarkable difference between drilling through drywall and drilling through plumbing pipes. Drywall is basically compressed chalk, just don't press hard and force the drill through anything that doesn't just give way on its own.
    – leigero
    Dec 1, 2016 at 20:11
  • If it got we once but it no longer getting wet, then it will dry out with no serious mold formation. The bathroom is on the 2nd floor above the living room, right? There is almost certainly no insulation in the space between two stories. If the stain was near an outside wall, then wall insulation could get wet, but would probably dry out in time. But if you have to check by drilling I would drill until you just pierce the drywall and then insert a screwdriver or a wooden dowel to feel for plumbing or wiring. Borescopes are available for a reasonable price and come in handy all the time. Dec 1, 2016 at 21:38

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