Mason Hearth Clearance to Combustibles?

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Hexa Fox

Member
Sep 19, 2023
206
West Virginia
Hey guys,

I am very close to completing my install. However, as @begreen and @bholler mentioned I need to make certain that minimum clearances are met. We went over this in the past and something led me to believe I was okay. It could have been that the DuraLiner I selected is a zero clearance product. What I did not account for is I doubt the thin stainless steel stuff that is going to run through the masonry thimble is also a zero clearance product.

My father built this hearth when I was very young and unfortunately is no longer with us. The only thing I can tell you is that the first layer of bricks clearly goes beyond/inside of the drywall. I can take a picture of that. The first picture is what I am planning on running through my thimble and the second one is my actual thimble that is going to go into the tee connection. It is also worth mentioning that my thimble is a 8" rather than a 6".
[Hearth.com] Mason Hearth Clearance to Combustibles?[Hearth.com] Mason Hearth Clearance to Combustibles?
 
Hey guys,

I am very close to completing my install. However, as @begreen and @bholler mentioned I need to make certain that minimum clearances are met. We went over this in the past and something led me to believe I was okay. It could have been that the DuraLiner I selected is a zero clearance product. What I did not account for is I doubt the thin stainless steel stuff that is going to run through the masonry thimble is also a zero clearance product.

My father built this hearth when I was very young and unfortunately is no longer with us. The only thing I can tell you is that the first layer of bricks clearly goes beyond/inside of the drywall. I can take a picture of that. The first picture is what I am planning on running through my thimble and the second one is my actual thimble that is going to go into the tee connection. It is also worth mentioning that my thimble is a 8" rather than a 6".
View attachment 323050View attachment 323051
There is no way for us to know from pics. And you really can't use black pipe buried in the wall. It looks like you need a 3 or a 4 foot long piece of stainless and the stainless should run into the room. Any joints riveted together in the wall
 
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There is no way for us to know from pics. And you really can't use black pipe buried in the wall. It looks like you need a 3 or a 4 foot long piece of stainless and the stainless should run into the room. Any joints riveted together in the wall

Thanks! So is there a way I can figure it out without drilling a hole? I cannot comprehend how I would be worse off with a metal liner inside the thimble when we have ran stove pipe directly to that thimble and let the smoke openly exhaust through everything.

I got some Cobalt bits today to drill through the stainless steel. I am replacing that small black adapter with a stainless adapter that I am suppose to receive tomorrow. Having that in mind, the large piece to the left is an adapter to adapt the double wall pipe to the pipe that is going to run to the tee. That the single wall side of that pipe has to go into the thimble.

Please correct me if I am wrong but there isn't anything technically wrong with me doing it this way correct? Just I may have to replace that thimble adapter every few years or something? The way that I am setting this up should make this piece manageable to replace when needed as well.
 
Thanks! So is there a way I can figure it out without drilling a hole? I cannot comprehend how I would be worse off with a metal liner inside the thimble when we have ran stove pipe directly to that thimble and let the smoke openly exhaust through everything.

I got some Cobalt bits today to drill through the stainless steel. I am replacing that small black adapter with a stainless adapter that I am suppose to receive tomorrow. Having that in mind, the large piece to the left is an adapter to adapt the double wall pipe to the pipe that is going to run to the tee. That the single wall side of that pipe has to go into the thimble.

Please correct me if I am wrong but there isn't anything technically wrong with me doing it this way correct? Just I may have to replace that thimble adapter every few years or something? The way that I am setting this up should make this piece manageable to replace when needed as well.
Read the liner manufacturers instructions. Every one I have ever read required stainless all the way through the wall into the room. As far as checking for combustibles I typically just drill some test holes through mortar joints to see what I hit
 
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Read the liner manufacturers instructions. Every one I have ever read required stainless all the way through the wall into the room. As far as checking for combustibles I typically just drill some test holes through mortar joints to see what I hit
Thanks for all the help. So I bought a kit that is suppose to come with everything that is needed to fully install this system. My problem is I guess my thimble is longer than typical horizontal runs. So what you see on the floor there is all from them (DuraLiner) but it consists of one extra stainless sleeve. The only thing that does not 'belong' is the adapter for double wall to masonry adapter. Again I plan to replace the small black piece with a stainless piece. This is the piece that is suppose to connect the stove pipe to the tee. Again you see that on the ground there.

If I can install it like this I could have the stove up and running in a day or so.

 
If their instructions say that's how you do it then that's how you do it. But that many joints buried in the wall sounds like a bad idea to me
 
^^ With stainless steel rivets.
Can anyone direct me to where I can find actual/quality stainless steel rivets? A lot of this kind of stuff on Amazon and even local stores cannot be trusted. Right now I am use self drilling screws with a pilot hole several sizes smaller than the screw and they are not getting very tight. I may need to pull them out and replace with rivets.

By the way for anyone reading, the difference of using Cobalt drill bits and a little cutting oil on stainless is mind blowing. I'm certain this is common knowledge for most people on here but it sure wasn't for me lol.
 
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They're not uncommon. Our local ACE hardware store carries them.

Thanks, the problem is I don't have a local Ace Hardware. I checked and my local Home Depot does not carry stainless rivets either.
My bigger problem is that I talked to my mom about the hearth again and asked her if she remembers if was framed. She said she is not 100% but she remembers the hearth being built over top of the drywall and studs. As in it was already there.

I know pictures cannot tell you what is behind it but it looks like the brick could be up against studs. I was hoping to fire up the stove soon because of how cold it has been.

So does having the pipe in the thimble really make a difference? Because we used to vent our wood stove directly into this thimble before.
[Hearth.com] Mason Hearth Clearance to Combustibles?
 
Hmm, that's odd.

[Hearth.com] Mason Hearth Clearance to Combustibles?
 
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Thanks, the problem is I don't have a local Ace Hardware. I checked and my local Home Depot does not carry stainless rivets either.
My bigger problem is that I talked to my mom about the hearth again and asked her if she remembers if was framed. She said she is not 100% but she remembers the hearth being built over top of the drywall and studs. As in it was already there.

I know pictures cannot tell you what is behind it but it looks like the brick could be up against studs. I was hoping to fire up the stove soon because of how cold it has been.

So does having the pipe in the thimble really make a difference? Because we used to vent our wood stove directly into this thimble before.
View attachment 323184
Yes and if the pass trough is done incorrectly the wood will slowly pyrolize dropping the ignition point lower and lower.
 
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Yes and if the pass trough is done incorrectly the wood will slowly pyrolize dropping the ignition point lower and lower.
I hate bad news. So realistically I should have someone come and look it over?
EDIT:
So can you tell me would this happen regardless? Like wood the wood pyrolyze from venting the wood stove directly through the masonry thimble or would having the hot single wall pipe make it worse somehow? Sorry I am just like things to make sense to me.
 
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I hate bad news. So realistically I should have someone come and look it over?
EDIT:
So can you tell me would this happen regardless? Like wood the wood pyrolyze from venting the wood stove directly through the masonry thimble or would having the hot single wall pipe make it worse somehow? Sorry I am just like things to make sense to me.
It would happen regardless
 
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I know assuming is bad but since it has been like that for around 35 years could one assume that there is a good chance it was done properly? By the way I seriously do appreciate the help. You guys have been great.
No it absolutely is not safe to assume that.
 
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You sir have greatly over estimated the availability of my local West Virginia Home Depot in the middle of nowhere. Type 25414 as the zip code and look for the Ranson, WV one. They have no stainless rivets in stock.
At least there's a Home Depot. It's quite a distance for us.

Looks like they are available at the Winchester store.
 
Methinks with each burning season the chances of getting the studs to their (decreasing) ignition temperature with the heat from the flue get larger and larger.
So it having been like this for a long time does not imply it's safe. Instead it is getting more dangerous by the year because of the slow decrease of ignition temperature due to pyrolysis.
 
This is my Frankenstein creation
Methinks with each burning season the chances of getting the studs to their (decreasing) ignition temperature with the heat from the flue get larger and larger.
So it having been like this for a long time does not imply it's safe. Instead it is getting more dangerous by the year because of the slow decrease of ignition temperature due to pyrolysis.
Thanks for stopping by. I think I will take my chances burning through it now then. The man who helped my father build it is actually a very well known brick layer in this area. He is retired now but the man definitely made a name for himself. Everyone seems to know him. I obviously know this does not mean it is 100% okay but I am investing a little faith that he knew what he was doing. After it gets nicer outside I am probably going to call someone and have them inspect it. There is a company here that actually does that and I am sure that is one of the concerns I can raise that they will check on.

On that note, here is what I have done. Every joint has three self tapping screws and a piece of this high heat tape that with my luck is not rated for this purpose. I plan to reach into the thimble and use high heat silicone to seal the last joint where the telescoping pieces go together.

EDIT: Well just read that this tape is not suppose to exceed 300 F. So awesome.
[Hearth.com] Mason Hearth Clearance to Combustibles?[Hearth.com] Mason Hearth Clearance to Combustibles?
 
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One last remark. Code has been updated because what was considered good long ago resulted in too many deaths.

Of course that's probabilities (not everyone has house fires) and not s guarantee.

Please do have good smoke detectors so you get warned early if chit hits the fan.
 
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One last remark. Code has been updated because what was considered good long ago resulted in too many deaths.

Of course that's probabilities (not everyone has house fires) and not s guarantee.

Please do have good smoke detectors so you get warned early if chit hits the fan.
Thank you for reminding me, I may install one closer to the wood stove. Our neighbor right across the street moved here because their old house burned and within the last decade our neighbors home completely burned to the ground. I will never forget that night, even though it was not our house I will never forget how vulnerable it made me feel. They were inside the house when it started and the fire took off so fast they were lucky to get out of the house. One second it was a small fire and when I got off the phone with 911 and looked again the entire house was on fire.

I am going to try to get everything into working order and have someone do an inspection.
 
This is my Frankenstein creation

Thanks for stopping by. I think I will take my chances burning through it now then. The man who helped my father build it is actually a very well known brick layer in this area. He is retired now but the man definitely made a name for himself. Everyone seems to know him. I obviously know this does not mean it is 100% okay but I am investing a little faith that he knew what he was doing. After it gets nicer outside I am probably going to call someone and have them inspect it. There is a company here that actually does that and I am sure that is one of the concerns I can raise that they will check on.

On that note, here is what I have done. Every joint has three self tapping screws and a piece of this high heat tape that with my luck is not rated for this purpose. I plan to reach into the thimble and use high heat silicone to seal the last joint where the telescoping pieces go together.

EDIT: Well just read that this tape is not suppose to exceed 300 F. So awesome.
View attachment 323229View attachment 323231
300 is not high enough at all
 
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The man who helped my father build it is actually a very well known brick layer in this area.
I would contact this guy and ask if he recollects how your father's brickwork was done. If you find him, ask him to come to the house to may help him remember. It's incredibly important to know what is surrounding that thimble.