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We built a porch whose back wall includes the masonry chimney. The chimney is sweating – not dripping, no running water, no leaks, sweating. There is no water on the floor around the chimney. It just sweats. We’ve checked the flashing a hundred times and it’s solid. We’ve sealed the chimney 3 times. Still, it sweats. It did get better after the sealing, but here it is again a few months later. I can’t believe it is a leak in the roof or flashing. I think moisture is penetrating the brick above the roof line and comeing out below the roof line. But, it has been sealed 3 times. Any other ideas?
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Is this chimney in use? If so, what is being exhausted by the chimney? Or, is it "sweating" with no exhaust gases going through it?
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This sweating is currently happening (July) so no, it is not in use. The cap appears to be intact but I have not checked out the cap myself so that is a possiblity.
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Well if the chimnney isn't in use for anything this isn't what I would call "sweating". I would call it visible moisture from a leak, source unknown.
But, this is one of those things we can all speculate about but only an inspection of the chimney and some creative troubleshooting will tell the answer. Two moisture sources I've encountered are from an exterior ash/cleanout hatch and from a wet base that was gathering ground water. Both were to a fireplace. You don't say what the chimney is used for so these may not be applicable to your situation.
Good luck and let us know what you finally discover so we can add it to the knowledge bank.
*NW..where do you live. Here in Louisiana in the spring and fall its not uncommon for insulated or non-insulated walls of carports and porches to "sweat". The humidity gets near 100% and the moisture collects all over the walls and ceilings. Could it be that the chimney surface temperature is near the dewpoint? Remember condensation always forms on the warm side of a cool surface. Maybe the bricks are cooler than the surrounding surfaces. This could be checked if you have a chart with the dew point on it and know the temperatures of both surfaces and the humidity levels.
*Do you have a gas heated water tank vented into this chimney? If so, then here's your possible moisture source.Davo
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We built a porch whose back wall includes the masonry chimney. The chimney is sweating - not dripping, no running water, no leaks, sweating. There is no water on the floor around the chimney. It just sweats. We've checked the flashing a hundred times and it's solid. We've sealed the chimney 3 times. Still, it sweats. It did get better after the sealing, but here it is again a few months later. I can't believe it is a leak in the roof or flashing. I think moisture is penetrating the brick above the roof line and comeing out below the roof line. But, it has been sealed 3 times. Any other ideas?