best caulk to use on chimney cap? (2025)

600 degree RTV silicone sealant

I picked some up from ACE last week

BrotherBart said:

Any 100% silicone caulk will do it better than fine. It sticks like crazy and doesn't vaporize until it gets to eight hundred degrees. If that cap gets to eight hundred degrees the last thing you are going to be worried about is what is happening up there.

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B² has it correct.

I've used silicone for stove gaskets when run out of the black gasket cement gunk.
But why caulk the cap itself ? Only The flue pipe and drain cap over the pipe to the roof are sealed with silicone--lasts for many years.

par0thead151 said:

at home depot, they have a 3M product that the home depot guy claims is the same.
is this true?

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The same as what?

Just get a tube of 100% silicone and go up there and goop that thing.

BrotherBart said:

par0thead151 said:

at home depot, they have a 3M product that the home depot guy claims is the same.
is this true?

Click to expand...

The same as what?

Just get a tube of 100% silicone and go up there and goop that thing.

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yep goop away! that flashing looks like it needs some love too!

RAMSAY said:

BrotherBart said:

par0thead151 said:

at home depot, they have a 3M product that the home depot guy claims is the same.
is this true?

Click to expand...

The same as what?

Just get a tube of 100% silicone and go up there and goop that thing.

Click to expand...

yep goop away! that flashing looks like it needs some love too!

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i still need to call the roofer, he came to look at it but i have not heard boo from him since then.
i have since, nailed it down and used the tar stuff ot seal it temporarily. however the wood underneath is rotten and will not hold the nails tightly, so i am going to have him replace that and re do it.
i hope that does not cost an arm and a leg

par0thead151 said:

the stove installer is here now.
he says that he needs to re align the flex liner so it does not put a sideways pressure on the cap. then he will silicone caulk it.
i would like to have a more secure means of connecting it, just thinking long term with a sweep running a brush up and down the liner each year...

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When that caulk dries it will be like that top plate is welded on.

well it is indeed caulked.
however the underlying issue remains, the liner is at a slant which is causing it to "pull" away from the masonry portion and create a gap. as can be seen in the photo. i will check on it in a couple days to see if it moved even more.
i just noticed now that there are four pre-drilled holes in the orange masonry square that they could have used to screw the cap to the masonry square.

i suppose this is better than nothing, however it looks like a amateur did the install, not a "professional"
I dont think i will be hiring a "pro" ever again, unless i can sit and babysit them while they work.
which defeats the point of hiring out int he first place. if i have to be up there i might as well be doing the work and save the $

how long should i wait to have a fire once the caulk has been applied?

ecocavalier02 said:

i think u could prob have one right away up there it would probably help it set up.

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should i be concerned about the corner on the right of the photo, there is a void in the caulk, i plan on filling it if the caulk does hold the cap in position for a week.
I realy wish they would have done it the right way and screwed the cap to the masonry, seeing as there are pre drilled holes there...

par0thead151 said:

ecocavalier02 said:

i think u could prob have one right away up there it would probably help it set up.

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should i be concerned about the corner on the right of the photo, there is a void in the caulk, i plan on filling it if the caulk does hold the cap in position for a week.
I realy wish they would have done it the right way and screwed the cap to the masonry, seeing as there are pre drilled holes there...

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you don't need it screwed down. i have almost the same exact setup . i just siliconed it on and that was it. try pulling it off onces its set. that aint goin no where. screwing ='s pia.