3m fire stop sealant combustible?

[Rob_Red]

Is 3m fire stop sealant combustible? Does it have the same consistency as caulking?

I am installing a through the wall thimble for class A and want to seal everything up since there’s no insulation in the thimble. I’m sure High temp silicon would do the job but if this stuff is even more heat resistant I may go this rout

 

[bholler]

Is 3m fire stop sealant combustible? Does it have the same consistency as caulking?

I am installing a through the wall thimble for class A and want to seal everything up since there’s no insulation in the thimble. I’m sure High temp silicon would do the job but if this stuff is even more heat resistant I may go this rout

What do the instructions tell you to use?

 

[Geoff C]

It is like damp clay with sand mixed in it and it dries hard.

 

[rijim]

It is an intumescent which means it will expand when heated to block off any gaps preventing fire & smoke spread. The products I am familiar with are fire heat and moisture resistant; does it have a diamond with an FM inside it?

 

[Rob_Red]

Sounds like a high temp silicone is the way to go, there are no specifics in the instructions for sealing a wall pass through, only roof mounted flashing where they do specify high temp silicone.

 

[Shrewboy]

I used this around my thimble on the inside of the wall, and on the inside of the framed out square of 2x4s to seal it up completely (no air gaps) and the outside where the pipe exits the wall:

Amazon product ASIN B007IBN0LA
Here is the video of me doing it, the silicone part is at 26:20, I am not 100% sure if this is the right way to do it but it has worked so far for me:

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[begreen]

A good quality silicone is fine. The outside of a proper thimble is not a high-temperature area. The function of the chimney wall thimble is to maintain the 2" clearance to the chimney pipe that is passing through the wall. (Note how close the wood is to the thimble. It is much more combustible than silicone.)

Shrewboy, the video is good but there is a problem that offset is only supposed to happen inside an attic or space where the elbow support bands are installed and an elbow support strap is tied to the nearest rafter to create a support system for the weight that is sitting on the elbows. This info is in the DuraPlus installation instructions. There is also an offset chart in those instructions. Only 2" clearance is necessary for this chimney pipe.

 

[Shrewboy]

A good quality silicone is fine. The outside of a proper thimble is not a high-temperature area. The function of the chimney wall thimble is to maintain the 2" clearance to the chimney pipe that is passing through the wall. (Note how close the wood is to the thimble. It is much more combustible than silicone.)

Shrewboy, the video is good but there is a problem that offset is only supposed to happen inside an attic or space where the elbow support bands are installed and an elbow support strap is tied to the nearest rafter to create a support system for the weight that is sitting on the elbows. This info is in the DuraPlus installation instructions. There is also an offset chart in those instructions. Only 2" clearance is necessary for this chimney pipe.

Thanks for that information, I actually thought the same thing, there wasn't anything to fasten those bands to on the side of the house. Do you think adding a block of wood to the side of my house and screwing it into that is OK? The top one is screwed into one of the studs inside the gable area. The other one is just screwed into the wall.

 

[begreen]

Thanks for that information, I actually thought the same thing, there wasn't anything to fasten those bands to on the side of the house. Do you think adding a block of wood to the side of my house and screwing it into that is OK? The top one is screwed into one of the studs inside the gable area. The other one is just screwed into the wall.

It would help. Give DuraVent tech support a call.