Help With Installing a Thimble On My Chimney

I need some help on how to fix my thimble to chimney. The thimble is a 8" inside diameter an the chimney is only 6". It is not even cetered on the chimney so I couldn't just put a six inch inside it and the mortar they had on the side came off so now there is a big gap. I wanted to put 8" pipe into the thimble but would not go in far enough because of the mortar being built up to fill the gap. Any suggestions would be great. Thanks

Fill the opening around the inside flue with a mix of 2 parts sand an one part Portland cement ..Available H d Or mason supply yard .Mix it stiff pack it in tight . jack Mason here retired .

There is nothing behind the gap to hold the cement just empty space. The sides of the flue are just there.

How about attach one of those trim rings to a piece of 6" pipe letting the pipe stick past the trim ring into the clay pipe about an inch or two. The trim ring would give you about 2" around the pipe allowing you to use the "mix" above or something similar to attach it to the clay part.

What size pipe coming from your stove..

I'm going to use 6" pipe.

I don't want to sound stupid but would hydraulic cement work or wouldn't it hold up to heat. if I put 6" stove pipe through it it will have an air gap. Thanks for the help

That's quite the Elegant Nightmare someone handed You !

It's a True Stinker chasing someone else's poor work,and unfortunately,it's all been dumped squarely in Your lap.....

I'm not much help right now,but I'm trying to think of a Refractory Rated Product that could be pumped or pushed completely around a 6" thimble to save the day for You.... I've got to go cut the grass for the 40th time this fall before a Thunder Storm filled Cold Front arrives here. That'll give me time to ponder.... You ignited this thought stream when You used the word "Hydraulic"..... Jack had a Good Thought,but the fact that You've got a blind circumference to work with is tough...

hkling wrote: ↑

Sun. Oct. 15, 2017 7:20 am

I don't want to sound stupid but would hydraulic cement work or wouldn't it hold up to heat. if I put 6" stove pipe through it it will have an air gap. Thanks for the help

Right, there will be a one inch air gap all the way around, between the 6 inch pipe and 8 inch thimble. Stuff it with ordinary fiberglass insulation. You might even be able to stuff insulation into that inside gap where the thimble is misaligned with the chimney. Fiberglass insulation will not burn and holds up to some pretty extreme temperatures, true story. I use it all the time, many others have as well. That would be the quick and simple way.

Do you think if I get a 6" thimble and push it all the way in until it rests against the flue could I put some cement with my hands from the inside to seal it? Maybe use something to center it more to the right since it is off center. Would the 3m fire blocker be okay to use between the thimbles?

Den034071 wrote: ↑

Sat. Oct. 14, 2017 6:44 pm

Fill the opening around the inside flue with a mix of 2 parts sand an one part Portland cement ..Available H d Or mason supply yard .Mix it stiff pack it in tight . jack Mason here retired .

x2.

There is nothing but space in that opening that is why the concrete came out to begin with. There is nothing to hold it in to pack it tight. If you could look at it from the side it is a 1 1/2" x 9" or so gap.

Spray foam, then concrete over.

hkling wrote: ↑

Sun. Oct. 15, 2017 11:05 am

There is nothing but space in that opening that is why the concrete came out to begin with. There is nothing to hold it in to pack it tight. If you could look at it from the side it is a 1 1/2" x 9" or so gap.

Put a little wire mesh in the gap and mix the concrete stiff, it will stay just fine. I had to do the same thing in a different house.

The problem is that there is no support for the pipe or thimble. Normally there is the distance of the brick surrounding the flue. This seems not to be the case here. the pipe will need some sort of exterior support because you can't cement in a pipe that only extends in an inch or so.