Mysterious spots on the ceiling

jimobaMarch 23, 2010

A few months ago, I noticed light brown spots on the ceiling in my living room and dining room (they share the same wall). At first, I thought it could be leakage from the windows in my master bedroom and office upstairs, which are directly above where the spots appeared. However, the spots are a few inches from where the wall and ceiling meet. The HVAC vents on the second floor, however, are located right above the spots, so I was thinking the source of the spots has something to do with the HVAC pipes. There is no plumbing on that side of the house, so a leaky water pipe seems unlikely. After very heavy rains last week, I noticed new spots in the dining room near the original spot; the shapes are kind of weird, so I don't think the source is a typical leak. I've posted pics of the spots in both rooms (the dining room is the one with the green walls). If I had the slightest idea what was causing the spots, I could call a repairman, but I wouldn't know exactly who to call, since I have what the cause is. Any thoughts?

Here is a link that might be useful: My mysterious ceiling spots

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Looks like water leak spots to me. The after rain increase in size strengthens that diagnosis.

Time to look in the space above the spots.

    Bookmark   March 23, 2010 at 4:32PM
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If it isn't water spots it could be due to a dead rat in the attic.

    Bookmark   March 23, 2010 at 5:56PM
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Second story above the room with the spots---probably not a roof leak.

    Bookmark   March 24, 2010 at 4:53AM
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If the HVAC vents are uninsulated metal, what you are seeing is probably the result of condensation forming on or in the vents.

Only solution in such a case is to insulated the vents or replace them with insulated vents.

If you have a humidifier on your HVAC system, have it might be a contributing factor if it is over-saturating the air.

    Bookmark   March 24, 2010 at 5:40AM
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Thanks, everybody for your comments; they're helpful.

I have to disagree with the dead rat theory (the space in question is between the first and second floors, and there are spots in two different rooms, although I haven't ruled out insects as a possible cause of the damage) and the roof leak theory, since there are no stains on the second floor ceiling or floors. My first thought was condensation around the HVAC vents (my HVAC has an integrated humidifier, but it's old and I've never used it), especially since they run pretty close to the exterior wall, and I don't know how much insulation is in the wall itself.

My next question: who would be the best person to call to investigate and repair the damage--an HVAC specialist, a general handyman who can repair drywall, or God forbid, an exterminator?

Oh, the joys of being a homeowner!

    Bookmark   March 24, 2010 at 11:57AM
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Ours was caused by water coming in just under the upper level windows. There was NO water damage evident around the windows (interior or exterior) or walls/floor of the second level, but somehow it worked its way down and started pooling in a few spots on top of the plaster of the ceiling of the lower rooms.

We had plans to gut the area we didn't worry about it - figured we'd find the problem at that time.

And sure enough, once all the plaster was removed you could see the path the water had been following. It simply did not show through until it reached a place where it started pooling - and this was a few feet away from the exterior wall in the lower level.


    Bookmark   March 24, 2010 at 12:44PM
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As others have said, that's definitely water spots. Problem with water is that it's a bi-polar molecule which tends to stick to itself, so it can run a great deal vertically before it finds a blockage, and then it puddles. In my old house, I had water spots show up on the ground floor ceiling caused by a leak in the second story roof, and not directly below the leak. Bottom line: The leak is *probably* close to where you are getting the spots, but not necessarily. If the leak gets worse when the rain is wind-driven, it *could* indicate a seam leak.

    Bookmark   March 24, 2010 at 5:22PM
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I agree with Cathy. That kind of water infiltration problem is common especially since the sills of many modern clad windows have poor sill overhangs/drips so eventually the horizontal caulking fails and water is drawn back into the wall cavity. I saw it happen in over a hundred units of a large condo complex on the ocean. Subsequently Andersen redesigned most of their window sills but many other manufacturers still have poorly designed sills.

    Bookmark   March 24, 2010 at 6:23PM
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I'd suspect poor flashing or incorrect caulking around the window. A garden hose directed at specifit points of suspicion helps in diagnostics.

    Bookmark   March 25, 2010 at 11:56AM
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Check the flashing around the roof vent pipes. The rubber seal drys out over time and wind and rain causes slow leaks down the black pipe.

    Bookmark   March 26, 2010 at 12:31PM
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Thanks for the insights about possible water infiltration. The spots haven't changed since my first post, even though we had some heavy rains and wind about a week ago. Now that the weather is warmer, I'll check around the second floor windows to see if they need re-sealing. If everything looks OK there, I'll just keep watching the spots to see if they change and under what conditions.

I appreciate all of your input!

    Bookmark   April 7, 2010 at 10:36AM
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have you looked at the ducts?
manhattan has the right idea based on your
original post.
if the spots are near ducts it is more than likely
condensation from leaky or uninsulated ducts.

of course it could be many things impossible
to diagnose without much more info..and without
seeing the actual house and config

what is your location?

    Bookmark   April 9, 2010 at 11:15AM
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I'm a handyman in Maryland and I had a customer with a big spot in his drywall like yours. Once I cut the drywall away there was the ducting for his dryer. The run had a low spot in it. When I cut the two sections of duct apart water started coming out. I quickly stopped it a grabbed a bucket. I had 3 inches of water in a 5 gal bucket come out of the duct. I was shocked. I thought the story would help.

    Bookmark   April 9, 2010 at 5:20PM
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It's most likely a moisture problem, say roof leaking or poor ventilation in the said areas of your house. We experienced the same thing before, twice actually - brown spots on our bathroom ceiling because we had no exhaust fan and spot on the dining area's ceiling as well 'cause of the a/c. We had to call not just an expert on HVAC but also an expert in painting in NY.

Here is a link that might be useful: expert in painting in NY

    Bookmark   April 16, 2010 at 4:03PM
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