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Oakie 06-10-2009 07:33 AM

Condensation on ceiling
First post:
We just bought a 15 year old 2 story log house with the interior finished with pine tongue and groove boards including the 28 foot cathedral ceiling in the living room which brings me to the problem. We noticed water dripping from the very top of the ceiling this spring on the warm days, after I finally got a ladder high enough to investigate the top boards at the very peak of the ceiling were covered in condensation and dripping. I pulled off the 1 inch trim boards that ran the length of the peak and they had black stains on the underside. The little bit of insulation I could feel between this area seemed moist, but I could only see btween a half inch crack. I left the trim boards off and we now have the 2 ceiling fans on low at all times with no further moisture. But at certain times in this room we have a "musty" smell, we have cleaned the carpets, furniture and windows, the room is spotless but still has a smell. Could I have mold behind the boards at the very top of the ceiling? There are no pipes in this part of the ceiling. Thanks

handyguys 06-10-2009 07:51 AM

From your description it sure sounds like you could have mold. Maybe not the toxic stuff but unpleasant regardless. Condensation forms when there is cold/warm areas meeting. like when you pull a cold beverage from the fridge and you get condensation on the outside of the container.

Log homes are particularly difficult to insulate. My guess would be that you do not have enough insulation in the ceiling or the insulation is not installed correctly. This is just a guess.

How might this be fixed? Cant say for sure. It could involve either building down a false ceiling to allow for more insulation. This would involve quite a bit of work inside to make it look right. Alternately - you could build up an attic on top of your existing roof. This too would be quite extensive and costly.

Another possible solution would be to investigate what type of insulation you have. If you have fiberglass batts under the T&G on your ceiling, and no attic or airspace above the fiberglass, I might just remove the T&G and the fiberglass and have spray foam insulation installed. This will better seal the area, serve as a vapor barrier, and not require airspace between the insulation and roof deck. While you are doing this you could also consider dropping the ceiling a few inches to gain more space for more insulation. When done replace the T&G and trim.

Good luck.

GBR 06-10-2009 03:57 PM

Is the kitchen nearby without a drop ceiling?
Or a laundry room, or bathroom, to give this moisture off?

Do you have a concrete slab floor? Be safe, G

Oakie 06-11-2009 05:26 AM


Originally Posted by GBR (Post 31291)
Is the kitchen nearby without a drop ceiling?
Or a laundry room, or bathroom, to give this moisture off?

Do you have a concrete slab floor? Be safe, G

The dining room is the next closest room, and we do have a concrete slab floor. I have been told the heat rises to the top of the cathedral ceiling and if the outside temp is slightly cooler condensation forms or if the humidity is real high. As long as the 2 ceiling fans are on there is no condensation.

GBR 06-11-2009 01:46 PM

Exactly. And the trim piece is not air tight, so I would suspect mold under. The insulation has gaps in it, or is not thick enough. The slab may be contributing to to the moisture supply. Did you check with plastic taped down, or is the slab radiant heated? Handyguys has some good ideas. I worked for a G.C., 5 years ago that built a slab on grade, cathedral roof, with wallboard walls. Six months later they had to rebuild it because of mold. In a high water table, no perimeter drains, no gravel sub grade, no vapor barrier at slab, no venting-bottom or top of individual rafters. Be safe, G

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