Clarification on 18" clearance to combustibles

[polyfractal]

Could someone provide clarification about single-walled clearances? I know single wall requires an 18" clearance to the wall or ceiling. Does this also apply to the location where the stove pipe meets the thimble? I'm assuming yes, but would like to verify.

Our setup currently looks like the attached pictures. VC Vigilant set on a raised hearth, ~40 inches from the back wall. The wall pass-through is a steel crock surrounded by ~12 inches of brick, which then connects to our masonry chimney. Single-walled stove pipe connects the stove to the chimney.

The wood paneling and drywall has been removed under the trim collars (so the collars are flat against the pass-through brick), but is still within about 3" of the edge of the pipe. I'm concerned this is too close.

However, if the 18" clearance is required, that extends really far to either side. I've not see photos setups like this, so I'm very confused. Do you have to put durock 18" around all sides? Doesn't that also mean you need to remove studs within 18" too?

Or does the 18" clearance only apply to large stretches of wall/ceiling that is parallel to the pipe?

 

[DAKSY]

That install is not correct. The wall collar should be sitting proud of the knotty pine, not recessed within it.
A clearance of 3" to that single wall pipe will eventually lead to a lower the combustion point of the surrounding wood.
You are going to have to change something in your set up to make it safe.

 

[polyfractal]

That install is not correct. The wall collar should be sitting proud of the knotty pine, not recessed within it.
A clearance of 3" to that single wall pipe will eventually lead to a lower the combustion point of the surrounding wood.
You are going to have to change something in your set up to make it safe.

Ok...any thoughts on how we should go about fixing it? The original install was worse, we are slowly attempting to fix the mess.

Can I cut a circle of Durock matching the recessed cutout, to allow the collars to sit flush? Or will I have to get some double walled pipe for the section near the wall?

 

[KindredSpiritzz]

I think it has to be 18 inches from anything combustible so it will have to get ripped out and covered in duroc but im no expert. Someone will chime in shortly on the correct install.
Probably have to have a 1 inch air gap too.

 

[Simonkenton]

"...should be sitting proud of the knotty pine..."

I like that. Never heard that expression before, must be Yankee slang, but I understand. The black collar should be flush with the wood and not recessed.
That is a weird install, never seen the collar recessed like that, looks like someone went to a lot of trouble to screw up the install.

You have asked a good question about clearance to combustibles, something that I am not clear on. Even if the collar is "sitting proud", obviously the pipe is still closer than 18 inches to the pine. Does the heat just radiate vertically from the pipe?

At any rate, if the single wall pipe is too close to the wall, you could install a heat shield on the wall, as I have done for my wood stove. This is copper. I got some 2 1/2 inch copper nails to keep the heat shield one inch away from the wall. Very effective heat shield.

 

[begreen]

The question here is whether that is a legal or safe thimble. Based on what I'm seeing I would guess not, but the right way to find out will require some surgery.
https://www.hearth.com/econtent/index.php/articles/passing_a_chimney

 

[polyfractal]

You have asked a good question about clearance to combustibles, something that I am not clear on. Even if the collar is "sitting proud", obviously the pipe is still closer than 18 inches to the pine. Does the heat just radiate vertically from the pipe?

At any rate, if the single wall pipe is too close to the wall, you could install a heat shield on the wall, as I have done for my wood stove.

Hehe, yep, this is exactly my source of confusion. I'm unclear how the 18" limit interacts with a wall patch limit (12").

Do you have a photo of where your stove meets the wall? How is the heat shield arranged there?

The question here is whether that is a legal or safe thimble. Based on what I'm seeing I would guess not, but the right way to find out will require some surgery.
https://www.hearth.com/econtent/index.php/articles/passing_a_chimney

This is what I'm confused about. We have a wall-patch like that article recommends. The wall patch is 12" of brick on all sides of the crock. The article is unclear what you are supposed to do with the surrounding drywall though. It says: "If the interior wall needs to match up to a being a flat surface, then non-combustible cement board such a Durock could be used on the interior finish."

Does that mean we need to cut the drywall / wood panel to match the 12" wall patch, then place Durock over the wall patch to keep it flush? Does the 18" clearance limit only apply if the wall patch is not in place?

Or does it mean we still need to cut 18" from the drywall and place a large circle of Durock over the entire patch, as well as the empty space around the patch? This confuses me, however, since the framing studs of the wall patch are necessarily within 18".

Attached is an image of the current setup and hopefully helps to explain my confusion better. Thanks everyone for the help!

 

[begreen]

Heat radiates in all directions from the pipe and convects vertically.

My understanding is that the patch needs to be non-combustible as well. One possibility is leaving the brick exposed. Or cover with painted or tiled durock if you want to bring the surface out flush with the wood. Or an 18" circle of sheet of metal with the crock hole in the middle.

 

[kennyp2339]

My one friend had a chimney fire 2 years ago, he filled a claim with his homeowners insurance because he had to replace the outside metal chimney, his setup at the time was 25 years old, his insurance paid for a whole new class A chimney, a new woodstove, and the install, I think he said something along the lines $4,000 claim at the end of the day. His pass through was through a masonry wall and the township insisted that his pass through be lined with triple wall pipe so looking at it from the stove collar he had to come out with singe wall 36" vertical then (2) 45deg bends into a class a triple wall pipe horizontal, the pipe went through the wall then into the connector T (with bottom clean out) then strait up to chimney cap. The townships interpretation of clearance to combustibles was quit literal and it actually makes sense on paper.

 

[polyfractal]

Heat radiates in all directions from the pipe and convects vertically.

My understanding is that the patch needs to be non-combustible as well. One possibility is leaving the brick exposed. Or cover with painted or tiled durock if you want to bring the surface out flush with the wood. Or an 18" circle of sheet of metal with the crock hole in the middle.

That makes sense...I'm fine with leaving the brick unexposed honestly. I just want it to be safe We're just confused because even if the brick is left unexposed (12" in all directions from the pipe), the drywall and pine will only be 12"....which seems at odds with the 18" rule.

so looking at it from the stove collar he had to come out with singe wall 36" vertical then (2) 45deg bends into a class a triple wall pipe horizontal, the pipe went through the wall then into the connector T (with bottom clean out) then strait up to chimney cap.

I was thinking of something similar as well. Could we:

1. Expose the 12" wall patch so that it is brick-only
2. Install a 12" section of double-wall pipe that connects to the thimble. This will bring clearance down to 6", so that should be fine with the 12" wall patch exposed
3. Transition to single-wall for the rest run into the stove (because we already have all the piping for that)

 

[begreen]

Normally single and double wall connector pieces don't mate, but maybe that would be possible? Or just go double-wall for the whole connector. It would look more finished and would help draft a bit by keeping the flue gases warmer.

 

[hearthnleisure]

We have really good luck with the Insulated Thimbles that ICC Chimney offers. This is basically a piece of stainless steel rigid liner on one end that will slide into the existing thimble opening. There is a mounting flange that will sit tight with the brick and get attached with masonry bolts. The remaining part that is seen in the room is more like Class A chimney pipe that allows for a much lower clearance around the protected part. There is a black sleeve and a trim ring that finishes it all up so it looks nice when complete.

It looks like there are two trim rings currently installed with your setup. If the thimble will allow for it, I would install a 7" or 8" thimble to eliminate the need for the stovepipe reduction in size at the thimble. You may even be able to break out some of the existing thimble to allow for the larger thimble to be installed. Depending on the size of the chimney flue, this could really help with draft and soot buildup.

Check it out here.