Cracked 8” thimble

[11Bravo]

I have a home built in 1986. The 8” clay thimble (crock) runs through a block wall in the basement. My pellet stove crapped out and I’m going back to a wood stove. Upon inspection, the 8” clay thimble is cracked in numerous places but still intact. My wood stove has a 6” pipe system. I’m thinking I can insert a 6” clay thimble through the 8” thimble provided the 6” thimble O.D. is not too large. If it slips in, I could seal the annular space using a thin slurry of mortar.
Has anyone done this or have other suggestions?

 

[kennyp2339]

insulated liner to a metal T snout then black pipe to the stove.

 

[11Bravo]

Thx Kenny. My chimney runs between the house and garage. Not sure I can connect the t snout to the pipe. No access except at the flue base inside, clean out. I do see snouts that can be installed with access through the thimble.

 

[bholler]

Thx Kenny. My chimney runs between the house and garage. Not sure I can connect the t snout to the pipe. No access except at the flue base inside, clean out. I do see snouts that can be installed with access through the thimble.

All snouts are attached through the thimble.

 

[11Bravo]

All snouts are attached through the thimble.

10-4. Never used one. So, would there be a need to seal the annular space between the two different pipe sizes? In other words, could stove gases flow through that gap?

 

[bholler]

10-4. Never used one. So, would there be a need to seal the annular space between the two different pipe sizes? In other words, could stove gases flow through that gap?

No but you should seal it just to stop air flow.

 

[11Bravo]

No but you should seal it just to stop air flow.

Thx. I’ll look at some vids. I’m still wondering if the 6” clay into the 8” clay is doable. I’m just a fan of masonry materials I guess.

 

[bholler]

Thx. I’ll look at some vids. I’m still wondering if the 6” clay into the 8” clay is doable. I’m just a fan of masonry materials I guess.

Do you know what condition the clay liners are in? Does the chimney have the required clearances to combustibles?

 

[11Bravo]

Do you know what condition the clay liners are in? Does the chimney have the required clearances to combustibles?

Chimney is solid. Old school masonry. Rectangular flue liners. I think the thimble cracking could have been a combo of heat and settling. It might be fine shoving an 8” pipe through then adapting with 6” to stove. The heat from the 8” through the cracked thimble might be nothing to worry about. Just trying to be safe as possible.

 

[bholler]

Chimney is solid. Old school masonry. Rectangular flue liners. I think the thimble cracking could have been a combo of heat and settling. It might be fine shoving an 8” pipe through then adapting with 6” to stove. The heat from the 8” through the cracked thimble might be nothing to worry about. Just trying to be safe as possible.

So you are running a 6" stove into an exterior 8x12 clay lined chimney?? When was the last time the mortar joints between tiles were checked with a camera? Checked for cracks? Does the chimney have The required 1" clearance from the outside of the masonry structure to any combustible materials

 

[11Bravo]

So you are running a 6" stove into an exterior 8x12 clay lined chimney?? When was the last time the mortar joints between tiles were checked with a camera? Checked for cracks? Does the chimney have The required 1" clearance from the outside of the masonry structure to any combustible materials

Yes. 6” stove pipe to 8x12. I realize this is not ideal for drafting but not uncommon. I’ve read the old train of thought was bigger is better. Now everything is 6”.
I’ve got a guy TVing the flue tomorrow. Based on my inspection it looks good.
The chimney is block with the clay liner. It travels up through the roof between the house and garage. Is this no longer acceptable construction?

 

[vbu]

Yes. 6” stove pipe to 8x12. I realize this is not ideal for drafting but not uncommon. I’ve read the old train of thought was bigger is better. Now everything is 6”.
I’ve got a guy TVing the flue tomorrow. Based on my inspection it looks good.
The chimney is block with the clay liner. It travels up through the roof between the house and garage. Is this no longer acceptable construction?

To be up to code all combustible materials need to have a 1" gap to the chimney if it's an exterior chimney

 

[bholler]

Yes. 6” stove pipe to 8x12. I realize this is not ideal for drafting but not uncommon. I’ve read the old train of thought was bigger is better. Now everything is 6”.
I’ve got a guy TVing the flue tomorrow. Based on my inspection it looks good.
The chimney is block with the clay liner. It travels up through the roof between the house and garage. Is this no longer acceptable construction?

It needed that clearance in 86 as well. What stove is this for?

 

[11Bravo]

To be up to code all combustible materials need to have a 1" gap to the chimney if it's an exterior chimney

Thx. I’ll get that checked

 

[begreen]

Yes. 6” stove pipe to 8x12. I realize this is not ideal for drafting but not uncommon. I’ve read the old train of thought was bigger is better. Now everything is 6”.

Going from 6" to 8 x 12 is not a good combo for drafting or keeping creosote down.

 

[bholler]

Thx. I’ll get that checked

If it's internal it needs 2"

 

[11Bravo]

If it's internal it needs 2"

I’m in VA. Codes here are (and have been) strictly enforced. I’ll double check with the county inspector.
This is just a basic small stove used to knock the chill out of the basement. No more than a few hours a night. Very minimal use.

 

[kborndale]

I’m in VA. Codes here are (and have been) strictly enforced. I’ll double check with the county inspector.
This is just a basic small stove used to knock the chill out of the basement. No more than a few hours a night. Very minimal use.

Even with light use, going from a 6" flue I to an 8x12 is most likely going to have poor draft and create a lot of creosote. A lot of creosote can lead to a chimney fire. This is when the clearance to combustibles becomes important as you don't want the chimney fire turning into a house fire. Most chimneys (especially older ones like you have) we're not built to code. Do yourself a favor and put an insulated SS liner in. The stove will burn better and cleaner and you don't have to worry about burning your house down.

 

[kennyp2339]

Smaller stove, light use into a bigger chimney means you’ll more than likely be fighting the stove with draft issues rather than enjoy the occasional fire.
I recommended the insulated liner because a cracked crock (from settling or moisture) generally can mean other parts of the chimney are in the same boat, one piece doesn’t settle, the whole thing settles, and additional tiles can be cracked, or the age of the mortar between tiles can be compromised.

 

[11Bravo]

Smaller stove, light use into a bigger chimney means you’ll more than likely be fighting the stove with draft issues rather than enjoy the occasional fire.
I recommended the insulated liner because a cracked crock (from settling or moisture) generally can mean other parts of the chimney are in the same boat, one piece doesn’t settle, the whole thing settles, and additional tiles can be cracked, or the age of the mortar between tiles can be compromised.

Thx. Any recommendations on type, brand, etc.!

 

[11Bravo]

Update 2/4/23
Chimney inspected and approved for use. Inspector Comments: Excellent workmanship, solid build, well-maintained in great condition.
Installed a U.S. Stoves EPA rated stove. 6” up through elbow to 8” increaser to thimble. Drafts very well. Super clean burn. Virtually zero detectable chimney smoke within minutes of start up. Hopefully this is the norm for this set up.
Thanks to everyone who took the time to provide advice and guidance.

 

[bholler]

Did they check for clearances?

 

[kborndale]

Hopefully it still drafts well after this arctic cold snap passes.

 

[11Bravo]

Hopefully it still drafts well after this arctic cold snap passes.

One can only hope. It was 36° today

 

[11Bravo]

Did they check for clearances?

Checked clearance on roof top. Otherwise it was built per 1986 code.