How do I air-seal the crack around a chimney?

user-917907 | Posted in General Questions on March 26, 2011 08:24am

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?

Answer

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Martin Holladay | Mar 26, 2011 09:31am | #1
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.
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Martin Holladay | Mar 26, 2011 09:53am | #2
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
user-917907 | Mar 26, 2011 08:45pm | #3
Thanks, Martin. Just the information I was looking for :)