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I recently looked at a newly constructed home for sale that had a small drip coming from a beam beneath a cathedral ceiling. The ceiling is pine, the roof is metal and it has continuous venting at eaves and ridge. There was no snow or moisture on the roof so I assume it is condensation in the roof structure. This was a warm day following a below freezing night. What might be the cause for this? Something blocking the venting? Any ideas? It’s a nice house but…
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"Something blocking the venting? Any ideas?"
Maybe the opposite: the ceiling might be too well vented so the ceiling paneling is getting too cold and the humidity in the air is condensing on the cold pine ceiling.
*Dear Chris,Yes that was condensation in the classic American defect house. I'm sure the vents are wide open. The water you see has evaporated off the foundation, travelled up the house, right through the ceiling, condensed on the roof, and dripped back down through the ceiling. We used to do this with small house models in school that they called stills.Here's a fun trick. If you can go back to the house on a cold, calm morning, crack the door open an inch. Feel the cold air flow in. There's the proof that the roof vents are working. They suck the warm air and moisture out of the house. Bad vents.After a year or so, the moisture content of the building materials will flash off and the condensation will stop. Then the house will just suck.Been there, FredBut that's just a theory.
*FredL,You've got to quit making jokes, I'm falling on the floor laughing.Chris,Warm moist air is escaping from inside the building envelope and condensing on the underside colder roof sheets and dripping back into the room. Either the house doesn't have a vb or a failure in it.Nothing complicated, nothing more than basics.
*Fred,Thanks for your reply. The plans called for a 6 mil plastic vapor barrier above the T&G ceiling but I wonder if it's there based on your info. It's not raining in there, just one small leak visible at this time however, the house has been vacant since completion and kept relatively cool. Should I suspect the worst and if so what would the solution be?
*LFred,In at least two other threads, you recommended removal of the siding in order to foam the back side of the drywall as the gold standard insulation practice. Would you similarly recommend removal of the roof in order to foam the cathedral ceiling? Is there any roof pitch at which you think this would not be a good idea?
*Chris,Normally this would be a situation for the builder of record to investigate and remedy. You can't discount the possibility that you may also have a leak.Regardless, the owner/seller/builder should address this issue prior to sale.
*Splinter,1.Is there any roof pitch at which you think this would not be a good idea? No2.Would you similarly recommend removal of the roof in order to foam the cathedral ceiling? No, it wouldn't be cost effective to do so unless the roof was overdue for replacement. We're presently doing a post and beam and we foamed it during the construction process prior to the roof sheathing installation.You certainly can foam from the inside as is the norm, it's just that in an older finished house, the exterior is normally the first to be replaced and it's nearly impossible to seal the house with any other means of insulation other than foam.