How to Extend a Wall Thimble?

[terryjd98]

I was tearing the wall apart today to get ready to install the stove vent pipe which I haven't bought yet, kit is on order at a lumber company. Got a bit of a suprise, the flat stone wall is 14 inches thick, no 2x4 studing. I was planning on gutting the lathe and plaster in the room and insulating it but now find the lathe and plaster was just attached to boards on the stone. So now I am going to have to stud the room so I can add insulation.
The thimble is going to have to be between 18 and 19 inches long. I will know for sure when I get the stone knocked out, then cement in where the stone does not come out even and put a stud wall up, insulation, drywall, all that fun stuff.
So the question is what do I use to extend the Wall Thimble? Some stove pipe the same size as the thimble? Have some 24 inch wide flashing I could cut, bend and pop rivet or screw to thimble. Guess thats another question would screws or pop rivets be better?
Any help would be appericated
Terry

 

[orangecrushcj7]

well, really all a wall thimble does is keep combustibles away from the hot stove pipe. I would think that metal flashing would work, and so would stove pipe of the same diameter. if you have masonry walls though, a thimble isn't even needed where the pipe passes thru. so the stock thimble should work fine - you'll have the coverage at the beginning of the inside of the wall where your new studs are, and the outside, which doesn't need it if it is masonry.

 

[terryjd98]

The outside has vinal siding on it so will need a couple of inches of protection and inside 4 inches but won't need any protection for the 14 inches in the center. I thought the thimble was suppose to be all one piece from outside to inside. If they don't have to be then a regular thimble will do it.
Thanks
Terry

 

[crausch]

OrangeCrush is exactly right. I recently installed my vent pipe through a Stone/block wall. My dealer told me the same thing. The 7" diameter part of the thimble is just to protect the combustionables. My dealer told me that when they do installs through non-combustionable walls, they just knock the outer ring off the thimble and run the pipe straight through.

I left my outer ring on. I then used flashing to extend from the outside piece of the thimble to the inside piece. I had a pre-existing 8" hole. That way I filled in between the outer ring of the thimble and the block with fire retardent spray insulation. Filling in the gap was really to keep any bugs or critters from getting in my block.

 

[djarseneault]

X3 Orange Crush is right on