Water stain on the ceiling

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Old 02-11-14, 04:59 PM
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Water stain on the ceiling

We noticed this water stain a while ago, and it seems to get worse recently. This is first floor ceiling of two story colonial. Above the ceiling is the exhaust venting pipe of first floor bath, towards the side of the house. So basically there should not be any water in the pipe. So when I saw the stain first time, my response was to look at the vent cover and re-caulk around it. But this stain seems to grow recently.

We live in Massachusetts, and the roof is covered with snow, and I am not sure if this might be the source of the water. However, I am very puzzled about how water get into the house. Any thought is welcomed. Thanks.
 
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Old 02-11-14, 05:53 PM
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The ductwork from your bathroom fan can get condensation collecting inside of it from the fan venting warm humid air + hitting the cold exterior air. The ductwork should be solid duct (not flex) as the flex will hold water and can sag. After the initial rise to get above the vent fan, the ductwork should pitch downward toward the point at which it exits the siding (so that it can drain as needed). The ductwork should also be fully insulated, and completely covered by your attic insulation until the point at which it exits the wall. (to help keep the ductwork as warm as possible)

That being said, it could also be an ice dam from snow melting on your roof. The ice dam occurs directly above your exterior wall and water running down the roof will back up under the shingles above that point. So that's also a possibility. Some people will hook up a hose to their hot water heater and melt a few clear pathways through the ice so that water doesn't back up. Of course, depending on the weather, the ice dams can occur and recur at will.
 
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Old 02-11-14, 07:39 PM
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XSleeper, Thanks for such a detailed explanation. The only thing is my first floor bath is half bath, so there is basically no humid air. Is that still possible causing significant condensation?
 
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Old 02-11-14, 08:36 PM
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Is there a 2nd floor bathroom directly above the 1st floor bathroom?
 
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Old 02-12-14, 02:20 AM
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There is no bathroom above the stain.
 
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Old 02-12-14, 02:28 AM
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Above the ceiling is the exhaust venting pipe of first floor bath
There must be water in this pipe that is dripping. Can you check it out?
 
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Old 02-12-14, 06:59 AM
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I hate to open the ceiling, although this might be the only way to find it out. But how can exhaust vent pipe from half bath contains water. There is no significant amount of moisture.
 
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Old 02-12-14, 07:31 AM
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Warm air hits cold air. poof, condensation. Same reason a can of soda sweats on the outside if the can.
 
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Old 02-14-14, 06:59 PM
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I would cut out the ceiling about 4" outside the perimeter of the stain. And, to minimize the cut line I'd use a sharp utility knife. If you're patient about cutting it, you'll end up with a very narrow cut line. When you go to close it up screw a couple of boards (1/2" or thicker plywood strips or 1x2 lumber) that staddle the opening, first to the ceiling, then to the cut piece, with drywall screws. Fill the crack and screw heads with spackling. Apply a stain blocker to the stained area. Then paint.
 
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Old 02-15-14, 05:46 AM
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Apply a stain blocker to the stained area.
make sure it's a solvent based primer, latex primers have a poor track record when it comes to sealing water stains.
 
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