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Stain in Ceiling

Our 1997 built home has what appears to be a water stain in our living room, yet we cannot find the cause and the symptoms themselves are puzzling.

The stain itself is about six feet long and about five inches across its widest part (at the center). The stain is very symmetrical and runs perpendicular to the 18" floor trusses which support the second story. The stain is also near (but not centered on) an a/c duct which runs between the trusses.

I cut a one ft square of sheetrock out to see if I could determine the cause. The sheetrock was not stained on the truss side nor did the truss of a/c duct work show any signs of moisture. I could reach some of the drains associated with the upstairs baths so we tried several experiments with running water in the upstairs baths, filling and emptying tubs, etc. No evidence of moisture could be found. I also reached over the the nearby a/c duct and didn't feel any moisture there either.

The only time I've seen a situation like this occur was when I had my garage re-roofed. The roofer put in a ridge vent even though we didn't have any other vents for the garage attic. In winter, cold air would fall down through the ridge vent and chill the attic space. Warm, moist air from the cars would rise and apparently condense along the ceiling sheetrock seams. But in our case, the stains aren't along the seams. We have an open concept floor plan at the back of our house so the kitchen and LR flow into each other, but the stain is well away from the stove, sink, and d/w areas.

I began my investigation some months ago. The stain remains about the same size (unfortunately, I didn't measure), but that may be attributable to the fact that my cutting open the ceiling changed air circulation.

Right now, though, I'm totally stymied. I don't know what the cause of the stain is or what can be done to address it. One the one hand, I'm tempted to enlarge the hole, wrap all pipes in the nearby truss area with insulation, patch & paint, and then hope for the best. On the other hand, I'd REALLY hate to revisit this problem in the future or leave a problem for some other home owner to cope with in the future.

I would very, very much appreciate ideas on how to proceed.

A. Spruce
Re: Stain in Ceiling

You say that there is bathroom plumbing nearby. If there is a bathtub, check the overflow gasket. It is likely that the gasket is loose or has failed, but the only time you'll get moisture there is when splashing around in the bathtub.

Re: Stain in Ceiling

We had some lighting work done in our home today (adding ceiling cans and pendants to our kitchen & LR). The electrician also had someone on his team who did drywall work so we asked them about the leak. They - like me - figured the leak must be in a drain otherwise a pressured line would hiss and show a lot more damage. We overflowed the bathroom sink and tub and flushed the toilet. (By "overflowed," I mean we ran water high enough to check that the overflow outlet on each fixture wasn't the source of the leak.)

When all was said and done, absolutely no evidence of a leak could be found. They speculated that a leak must have been a very small one given the amount of damage and perhaps the leak was "cured" by one of the following:

- shift in the house over the years
- material in the drain line clogging the leak
- the "glue" used in joining the PVC eventually flowed into the hole over time

Now the first two make sense, but I'm not so sure about the second. OTOH, even "solids" like glass flow so maybe it's within the realm of possibility.

In any event, they seemed dead certain there was no active leak and offered the patch the hole I made while they did the other drywall work.

As an aside, I have to say that we are AMAZED at how much lighting can change the appearance of a room. They took down the four-bulb fluorescent fixture centered on our kitchen island and replaced it with three pendant lights and seven canned lights. The kitchen now looks so, so much bigger! They also put three canned lights in our LR and changed out the cheap (probably under $40) chandelier in our 20' tall entranceway. I have the skills to change the entranceway figure, but not the 16' ladder or mountain goat skills necessary to do so.

All this ran us a pretty penny, but the house is so much better and we'll enjoy all this for the next 11 years we plan to be here.

Re: Stain in Ceiling

Have you tried spashing water around the valve trim plate. I have seen these leak while some one is in the shower.

Re: Stain in Ceiling

The other possibility is that you have a cold spot caused by the AC duct, possibly a leak in the duct, that is causing the warm moist air to condense in that area.

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