How do I air-seal the crack around a chimney?
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What are the best ways to seal either a Metalbestos-type or a masonry chimney as it penetrates the air/vapor barrier in a ceiling?
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Replies
Jack,
Check with the manufacturer of the metal chimney; install the necessary transition pieces and follow the manufacturer's recommendations for air sealing.
The crack around a masonry chimney should be sealed with metal flashing. The seams and edges of the metal flashing should be sealed with high-temperature silicone caulk.
Jack,
Here's a Fine Homebuilding tip from Charles Miller addressing your question. I think he should have installed caulk between the ceiling joist and the metal flashing, and he should have mentioned the need for high-temperature caulk at the flashing seams, but otherwise his advice is good:
Sealing an air leak next to a chimney
Thanks, Martin. Just the information I was looking for :)