Thermal Silicone opinion

[jawsont]

So I finished re-doing a fireplace-to-wood stove replacement comlete with exhaust through a stainless steel pipe via. a masonry chimney at my parents cottage in the past few weeks. Two weeks ago I put the stainless stovepipe through the collar onto the stove, screwed it in, and put a bead of thermal silicone around the joint. I also adhered the rain-cap flashing and chimney pipe rain-cap to the top of masonry chimney with a thick bead of thermal silicone as per installation instructions.

My father waited until I left to go home 3 hours later and promptly lit a stove despite me telling him that the caulking had a cure time of 24-48 hours. I grumbled at him about it and asked him not to do that again. I got back up this weekend, and put the finishing touches on the stovepipe's rain-cap and put a bead of thermal silicone around it's joint with the flashing cap (I only had 1/2 inch overlap between the two instead of the 1-1/2 as per instruction, and was worried about capillary action pulling the moisture back up the joint). My father waited until I left and promptly lit "a small fire to burn off the paper and scrap wood".

Any guesses if I should strip the system down and re-do the caulking? Two fires that might have lasted 15 minutes each and had no hardwood to 'ratchet the temperature up', but I'm worried that the integrity of the caulking might be comprimised.

Thks in advance.

 

[begreen]

Was a stainless steel liner installed in the masonry chimney? Most all silicone has a temp rating of ~400F. Some can go as high as 600F. But none are rated for direct contact with the stove pipe at the stove end. Up on the rooftop the flue gases are a lot cooler and it should be fine there.

I'm wondering why the storm collar was so tight on the flashing. If you can post some pics of the install we may be able to comment further.

 

[jawsont]

@ yes for the stainless steel liner. Good to know about the silicone @ the cap flashing. I won't worry too badly about that then.

The silicone at the exit of the stove is between the collar adaptor and the stainless flex pipe. This wasn't in the instructions (just 3 screws) but it seemed to me that there were gaps where mosquitos could be a problem in the summer (1/8" gaps depending on where the ribbing of the flex pipe entered the adaptor piece). Oh, he also painted the connection with black metal paint.

 

[bholler]

What is behind that tile???? Top looks good and the silicone at the bottom will not stay it will be way to hot. Is tht silicone on the bottom of the cap? if so how are you going to pull the cap off for cleaning?

 

[webby3650]

Typically a piece of rigid pipe is used at the bottom for aesthetics, painted black. I also am curious about whats
behind that tile, its super close! I also agree that silicone will not hold up in direct contact with the liner. Not even at the top, I've seen it fail there many times.

 

[webby3650]

Also, with the setup you've got there, sealant will not be needed anyway. Stove cement is the only thing that will hold up to these temps, but it just cracks and falls out. With a properly functioning flue, there is no real reason for sealant in these places.

 

[jawsont]

Ugly huge old mortared fire-bricks (white & bigger than "regular" clay bricks) are behind the tile. Well, technically behind the cement board we tapcon'd into the old ugly fire-bricks to hold the tile. The original brickwork fireplace was built around the fire-bricks. If that makes sense. We had to remove the bricks because the mortar was completely in shambles.

The reason I put the silicone down at the stove-end was because the bugs get pretty horrible up there in the summer and even a 1/8" gap would be a super-highway for the damn mosquitoes. When we were installing the plumbing up there we had finished the toilets etc... including the vent stack. At one point we didn't have the sink installed yet, but we did have the drain in - attaching to vent/septic - just not the trap or its sink. Well damn if we didn't get assaulted by mosquitoes in the middle of the night. We hunted the source.....they were pouring in through the open end of the pvc drain. They had sniffed their way down the vent, across the building inside the drain pipes in the walls/floor, and out the drain...or what would be the drain. Anyhow, that's why I was worried about plugging the small cracks around the collar down by the stove.

That red bead of silicone you see on the rain flashing(?) is my solution to the top that was supposed to slide down another inch. To clean the flex-pipe I'll have to cut the silicone bead and put in our brush there. The flashing itself is permanent-ish looking at the install guildelines. You are supposed to put a thick bead of silicone all around the top of the chimney and then press the flashing down onto it.

 

[bholler]

yeah you don't ever want to caulk a cap on like that good luck getting it off.

 

[begreen]

For frame of reference. The safety of the fireplace install is still in question.
https://www.hearth.com/talk/threads...tall-into-an-existing-brick-fireplace.129851/

 

[bholler]

oh its that fireplace

 

[bholler]

did you ever check the clearance to combustibles? they look way to close