All started with a bat issue in an attic where brick chimney rises directly through the peak of a 12-pitch roof (passes through framed opening with several inches of clearance. Some fiberglass insulation had been shoved between the chimney and the framed opening.on all four sides. I removed this (the upper portion was loaded with bat turds–nice).and found a nice little nook that bats enjoyed hanging out in, and could spot daylight in a couple spots where the chimney exited the roof sheathing (the light was coming in from under the lead flashing mortared into the chimney, I believe).
So what’s the proper way to seal the chimney as it passes through the roof? Should this be accomplished from the interior side by filling the space between the chimney and the roof framing with a noncombustible, flexible material of some sort?
Thanks for the advice.
Replies
Sounds to me like the real problem is bats getting into the attic. They crawled up into that space next to the chimney because they like to roost in narrow vertical slots. Says nothing bad about the chimney arrangement per se.
Generally, the flashing on top "seals" the chimney penetration through the roof. With a proper flashing job you MIGHT be able to see an occasional sliver of light sneaking through, but you shouldn't see a lot, and you shouldn't be able to directly see the sky.
The other sealing that needs to occur is at the boundary of the insulated "envelope", which generally is the attic floor/ceiling below in conventional construction.
I was thinking the bats are gaining access at the chimney, not elsewhere. I could be wrong about that, but I'm pretty sure that's what happening.
Doesn't seem right that I'm able to see any daylight there--it's not much, but doesn't take much of a space or gap for a bat to crawl in.
Also, from an energy efficiency standpoint it would be best if that was closed up properly.
So is it that the lead flashing wasn't properly sealed down on the roof surface by the roofer? I'm guessing the masons left the flashing there for the roofer to finish and he just did his shingling and bent the flashing down haphazardly. But I'll have to go investigate up there.
Is the proper thing for the flashing to be sealed/fastened down over top of the shingles?
I do see a bunch of ice and water shield when I look up from the inside. No signs of water getting in.
Based on your description and on what I havve seen, Dan is wrong, The bats got to the space by crawling up under the lead flashing.
Get some Roxul insulation to stuff back in, nail metal scraps to the bottom of the joists and then push the lead laps snug to each other on the outside.
and see the site adress in my sig line. Glad I caught you. Not here much anymore since they did this to the site
Just don't have gaps that bats can get through. (And screen the top.)
screening the top
Screening the top is a good idea in theory, but I found that the screen can quickly clog with fly ash, etc. and then there goes your chimney draft (I have a very clean burning Vermont Castings Encore vented through a 8-inch flue). In 10 years I've had exactly one dead bat I pulled out of the cleanout, so in my experience they don't tend to go into the flue. They're looking for tight vertical spaces that form a cozy slot for them to sleep in during the day. Putting a screen on during the summer's not a bad idea, though again I've bothered and never had bird issues.
Some types of birds love to nest on the draft ledge, if there is one. And then there are squirrels, who can do untold damage if they get into the house.
The screen need not have especially small openings. I doubt that bats can get through half-inch expanded metal, eg, but the openings are still about 0.44 x 0.94". You might clog that if you're blowing a lot of trash up the chimney, but not if you're really "clean burning".
Code requires any chimney screening to be have a minimum of 3/4" opening except in CA, which is 5/8".
Then go to 3/4" expanded
Then go to 3/4" expanded metal, or heavy 3/4" hardware cloth.
masonry for the chimney and Copper for the flashing. Lead is common because it is easier to work on site, but any good sheet metal man can break CU to fit
Thanks Pif. So no need to seal the flashing I gather--just bend it down as much as possible as you say. And seal things up from the inside where the framing is around the chimney. I can handle that.
I'll check out the other forum you suggest. What's the big change here anyway, the ads? Maybe I'm missing something.
I hope you're having a good summer on the island. Had a client over there last year, pretty sure I passed your driveway a few times.