Question regarding cathedral ceiling with condensation issue.
Last Post 18 May 2022 10:07 AM by newbostonconst. 3 Replies.
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brianbuntzUser is Offline
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17 May 2022 02:41 PM
Hello there, My wife and I recently bought a house in Northern California and as we were closing, we noticed a roof leak after a rain. The roof has a cathedral ceiling and is a pyramid in shape with a skylight. The roofer believed the skylight was not the issue. The roof is nearly brand new. Removing the affected section of the roof revealed that the closed-cell spray foam was wet (and had yellowed from its original white color). Our hunch is that the spray foam was installed incorrectly and that it has some air gaps. The western portion of the roof could be affected because of the heat gain from the afternoon sun driving the moist air from the wet shingles toward the cool air in the house where it condenses. My questions are -- 1) why do you think the moisture seems to have condensed in a band rather than uniformly near the top of the roof? 2) what might it take to fix the problem? The roofer recommended installing eyebrow vents all along the top portion of the roof, but they are not connected to soffits. Another idea would be remove the roof and plywood, install skip sheathing to create an air gap. The new roof would haves new soffits along the lower edge of the roof and vents near the top portion of the roof. New plywood would be attached to the skip sheathing along with roofing. It would look something like the diagram attached, but with the closed cell insulation. The other attached pics show the yellowed damp foam, the ceiling with water damage. Any feedback greatly appreciated!

Attachment: IMG_5849.jpg
Attachment: IMG_0708.jpg
Attachment: 1347se.jpg

newbostonconstUser is Offline
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17 May 2022 05:43 PM
I would question the flashing to that vertical wall on the left. The top of the roof joints show some discoloration also. Your cutaway is the right way to do it but I am guessing to do it that way you won't have enough insulation after that.

This must be one of those arch designed houses that is near impossible to build correctly.....I frequent Aspen and they have the same disease.


"Never argue with an idiot. They will only bring you down to their level and beat you with experience." George Carlins
brianbuntzUser is Offline
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17 May 2022 06:37 PM
Thanks for the feedback. And yes, it was an architect-designed house. We initially thought the old skylight was involved in the leak. We planned on replacing it in any case. Was the flashing near the skylight what you were referring to? To ensure we have enough insulation, we could make the whole roof higher and include rigid insulation over the spray foam (as in the attached).

Attachment: Roof-insulation-retrofit_0.gif

newbostonconstUser is Offline
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18 May 2022 10:07 AM
updated picture

Attachment: IMG_5849_(1).jpg

"Never argue with an idiot. They will only bring you down to their level and beat you with experience." George Carlins
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