Single wall liner, riveted vs. twist lock

[tsh2002]

Hello:
We will be installing a new 6 inch stainless liner to an existing masonry chimney this fall, which currently has 8 inch square clay flues in it. Unfortunately a double wall liner will not fit, so we're OK with a single wall liner, as the chimney is mostly indoors (in the middle of the house, not on an outside wall) except for a few feet at the top.

The main difference I can see between the single wall liners is some are riveted together, and some twist lock. It would seem that the twist lock might be easier and to me, maybe would hold up better over time? Has anybody had any issues with riveted liners working loose or any problems with them? The other thing I wonder is how tricky it is getting the holes to line up, etc. I've never dealt with this before, definitely looking for any feedback between the two types, riveted vs. twist lock.

Thank you very much.

 

[Ctwoodtick]

are you insulating the liner?

 

[tsh2002]

are you insulating the liner?

No, unfortunately a double-wall liner will not fit. But as mentioned most of the chimney is indoors, only the top few feet will be un-insulated, and the masonry wall is fairly thick.

 

[bholler]

No, unfortunately a double-wall liner will not fit. But as mentioned most of the chimney is indoors, only the top few feet will be un-insulated, and the masonry wall is fairly thick.

Does the chimney have the required 2" clearance to combustibles between the outside masonry structure and any combustible materials? If not the clay needs removed to allow room for insulation

 

[tsh2002]

Does the chimney have the required 2" clearance to combustibles between the outside masonry structure and any combustible materials? If not the clay needs removed to allow room for insulation

Yes, we are well above that limit. We are simply adding the stainless liner as an extra layer of protection at this point, and to help a little with the draft with the 6" diameter.

 

[bholler]

Yes, we are well above that limit. We are simply adding the stainless liner as an extra layer of protection at this point, and to help a little with the draft with the 6" diameter.

Are you sure? It's very rare to have that clearance

 

[tsh2002]

Are you sure? It's very rare to have that clearance

Yes, if I'm understanding the requirement correctly. We went with a masonry chimney because I wanted a more permanent solution vs. using pre-fab products.

 

[bholler]

Yes, if I'm understanding the requirement correctly. We went with a masonry chimney because I wanted a more permanent solution vs. using pre-fab products.

Is there anything that can burn touching the outside of your chimney

 

[tsh2002]

Is there anything that can burn touching the outside of your chimney

Only in a couple spots there is drywall and cement board touching the very outside of it, for example at the ceiling and in the attic near the trusses. So, just to confirm, the final cross section of the chimney (from inside out) would be: 6 inch stainless single wall liner, 8 inch square clay flue, 0.5 inch air gap for clay flue expansion, 4 inch of solid chimney block, and 5 inches of concrete block and stone, then the drywall/cement board.

 

[bholler]

Only in a couple spots there is drywall and cement board touching the very outside of it, for example at the ceiling and in the attic near the trusses. So, just to confirm, the final cross section of the chimney (from inside out) would be: 6 inch stainless single wall liner, 8 inch square clay flue, 0.5 inch air gap for clay flue expansion, 4 inch of solid chimney block, and 5 inches of concrete block and stone, then the drywall/cement board.

Well cement board isn't a problem the drywall is. No wood within 2"?

 

[tsh2002]

Well cement board isn't a problem the drywall is. No wood within 2"?

For most of it, no. However in the areas where there is drywall/cement board, their thickness is 0.5 inch, then there is the wood truss/wall joist behind that.

 

[Ctwoodtick]

I would just break out the clay and insulate the liner. Safer and you can upgrade to a heavier grade liner if you want. Little more expensive but it will probably last a lifetime. With the insulation, you will likely have less buildup and perhaps you could extend your sweeping schedule bc of it, saving either money or time there to offset your costs.
I’m saying this as someone who has used both insulated and uninsulated liners and sweeps the liners annually. Big difference.

 

[tsh2002]

I would just break out the clay and insulate the liner. Safer and you can upgrade to a heavier grade liner if you want. Little more expensive but it will probably last a lifetime. With the insulation, you will likely have less buildup and perhaps you could extend your sweeping schedule bc of it, saving either money or time there to offset your costs.
I’m saying this as someone who has used both insulated and uninsulated liners and sweeps the liners annually. Big difference.

I've thought about that, or trying to see if there's a way to use an insulated liner inside the clay flue. However since most of the chimney is inside, and I'm also insulating it with fiberglass in the attic, we thought about seeing how it goes. My understanding is that with the cat stoves (we are looking at the Ashford 30), the buildup should be minimal anyway.

 

[Ctwoodtick]

I've thought about that, or trying to see if there's a way to use an insulated liner inside the clay flue. However since most of the chimney is inside, and I'm also insulating it with fiberglass in the attic, we thought about seeing how it goes. My understanding is that with the cat stoves (we are looking at the Ashford 30), the buildup should be minimal anyway.

It should be. I’ve never had a cat stove but I bet the buildup could occur really fast one the cat is starting to fail. Not sure if the stove you’re using requires one but worth confirming that in the manual.

 

[bholler]

For most of it, no. However in the areas where there is drywall/cement board, their thickness is 0.5 inch, then there is the wood truss/wall joist behind that.

In that case you need insulation to meet minimum code remove the clay and do it right

 

[bholler]

I've thought about that, or trying to see if there's a way to use an insulated liner inside the clay flue. However since most of the chimney is inside, and I'm also insulating it with fiberglass in the attic, we thought about seeing how it goes. My understanding is that with the cat stoves (we are looking at the Ashford 30), the buildup should be minimal anyway.

Not true at all cat stoves are able to run at much lower flue temps making the insulation even more important

 

[tsh2002]

Thanks for all of this feedback and the information. I will look in to this more.

Back to the question on the liners, is there really any advantage of the riveted ones to the twist lock, or is one better than the other in any way?

 

[bholler]

Thanks for all of this feedback and the information. I will look in to this more.

Back to the question on the liners, is there really any advantage of the riveted ones to the twist lock, or is one better than the other in any way?

I don't know of any twist lock liners honestly. I really only use heavy wall flex liners for wood. Very few people use rigid liners at all anymore there really is no benifit

 

[begreen]

Thanks for all of this feedback and the information. I will look in to this more.

Back to the question on the liners, is there really any advantage of the riveted ones to the twist lock, or is one better than the other in any way?

I have only seen twistlock in gas rigid pipe, not all-fuel.

 

[tsh2002]

Thank you for all of the info and the feedback. Interestingly, I have found that Duravent makes an dual wall insulated liner that looks like it will fit inside the clay flues: https://duravent.com/duraliner/. We are checking in to it, a rigid and flex option is available, and it is riveted together in the 6" size. Seems like good stuff.

 

[begreen]

That was my first thought but I didn't suggest it because it is very close. Measure carefully. Duraliner's 6" liner ID is only 1/4" smaller than a typical 8" flue tile ID (6 5/8" vs 6 7/8") , and that is if it is perfectly aligned all the way down and with no mortar ooze.

 

[tsh2002]

That was my first thought but I didn't suggest it because it is very close. Measure carefully. Duraliner's 6" liner ID is only 1/4" smaller than a typical 8" flue tile ID (6 5/8" vs 6 7/8") , and that is if it is perfectly aligned all the way down and with no mortar ooze.

I've checked, and we have a very straight clear shot in the clay flues, there is hardly any mortar ooze so it appears it would fit. Will have to talk to our local dealer to see more. Thanks!

 

[tsh2002]

Just following up to this post a while back, in case it will help others. We ended up going with the solid Duravent Duraliner https://duravent.com/duraliner/ and very happy with it. As they state, it's about 6-5/8 for the outside diameter. So basically it is a 6 inch inside pipe with an extra 5/16" of insulation around it to make up the extra 5/8". Each piece sort of snaps together and there are 4 rivets that lock them in place, but the way they form together it's a solid insulation barrier. The only problem was it took 3 months to get it due to material and production issues. Just installed it this past weekend. Even though it is designed to be installed inside standard square clay flues (7" inside diameter), this only leaves 3/8" of space for each edge. We were very careful when we installed our clay flues and only picked ones that were at least 7" inside, and also very careful about keeping them lined up. If you have mortar ooze or the flues aren't lined up, I can see problems could come up with installation of this liner. When installing it, once in a while it would catch on the lip of the clay flues. When this happened, we'd simply twist it and it would then release and drop down further. It's also heavy, each 48" piece weighs about 11 lb. We used a large C clamp to hold it when attaching each section.

 

[begreen]

Thanks for the follow up. I'm glad it worked out without having to bust out the clay liner.