Sealing around chimney ceiling pentration?

[char]

I have a stainless flue that comes through the ceiling surrounded by a ~18x18in black flashing. I want to make sure that it is as tightly sealed as possible.

What is the appropriate way to go about that? I imagine I should just be able to run a bead of caulk around the outside of the flashing where it meets the ceiling, but what about where the flue comes through?

 

[ericjeeper]

Yes but when you caulk the pipe to the flashing piece make sure you leave a small gap at the ends of your pass around.. That way if you do generate a leak on the rooftop. It can trickle down your pipe and make you aware.As opposed to filling the whole pan and then dripping out onto your drywall lid.

 

[Highbeam]

Let's see if I can guess on teh setup. Is this the ceiling support box that is square where it penetrates the ceing? And then you have a roof peneteration with proper flashing up above it? You are trying to air seal your living space by sealing the square support box to the drywall right?

This is good. Go in the attic and seal it from above. The caulk job can be ugly up there. Alternatively you can remove the 2 inch wide trim piece and caulk where the actual sheetrock is cutout for the ceiling support box, then replace the trim piece. Use regular caulk since you are outside of the 2" clearance to combustibles requirement for the class A.

Where the actual flue comes through is more difficult. At this location the black stove pipe transitions to class A insulated SS pipe. You can't really seal here since there is no way to make it look good, there should be no significant gap, and you are too close to combustibles for anything except high temp silicone or furnace cement. UGLY. Also as Ericjeeper said, any water will be evident.

Do you have a big gap there?

 

[char]

You've got the setup right.

I'll caulk it from the attic side here soon. Thanks for the tips.