How exterior air seal at chimney to wall interface? Chimney spalling.
Using a FLIR One, I’ve found a major source of air leakage into my house from around the fireplace mantel. Using a homemade blower door and a smoke pen I’ve discovered that the air is in fact entering from the exterior chimney to sheathing interface. While I’ve been able to find extensive discussion and documentation on this site how to handle through attic air gaps for a chimney, it’s been less clear to me how to handle this detail on the exterior wall to chimney brick intersection.
Appreciate any insight or examples others have undertaken to tackle this problem. While I’m open to the simple solution at the interior by just caulking the mantle to drywall joint, I’m most interested in the exterior detail to really solve this problem.
Also, secondary, is the spalling at the chimney brick face. I’ve had the top of the chimney repointed and capped with a rain cover, but spalling continues during freeze/thaw cycles. I’m concerned it may not be a bulk water intrusion issue but instead from flue gas condensation. Not sure how to isolate the problem.
I’ve attached a series of photos to support this question. Appreciate, in advance, responder’s help and advice.
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