Stone Chimney Replacement -- Go with Clay Flue or Stainless Schedule A?

[JJ3]

Our stone chimney had to be replaced -- it was pulling away from the house and I checked and it was 8" out of plumb -- yikes! A foundation company had attempted to stabilize it before we purchased it but told me this spring that there was nothing they could do due to risk of it falling on them. On the inside we have a Hearth Phoenix Wood Stove. When we purchased the house in 2015 a chimney inspector said the clay flue was cracked in multiple places (likely from previous foundation settling issues) and installed 6" stainless liner in the chimney which has worked great until the foundation started noticeably moving again late last year. See picture of the chimney.

We are going back with same construction but larger foundation. Construction is cinder block core and rock rustic stacked attached to cinder block.

I was planning to use 6" stainless Schedule A pipe on the inside of the cinder block core for the flue. But yesterday, when I talked with the chimney inspector who had previously installed the liner, he said that recently he has been seeing failures in the Schedule A chimneys after about 10 year and told me about several recent cases he's inspected where there were openings in the pipe section joints. He recommended to install 8'x8" clay flue liner instead of the Schedule A. He said that with flue liner if it cracks down the road that it is simple enough to put a new stainless line in it. But if we install the Schedule A chimney sections that if it fails after 10 years then we'd be back in the boat of having to dismantle the chimney.

Any thoughts on using Schedule A versus clay flue liner?

If I can get all the parts the contractor plans to start reassembly next week. I'm hunting a 6" clay thimble now, local hardware store said their distributor could get it to them in 3 - 5 weeks.

• First picture shows chimney before demo -- and hopefully how it will look when we are done.
• Second picture shows after demolition with the stainless flue line remaining
• Third picture shows the broken clay thimble through the wall. It appears the thimble had cracked with the foundation settling and some hot spots were escaping between the stainless liner and the stove pipe insert -- right where the 2 of those met. So good thing we took it down.

If we go with the clay flue liner which I am leaning to, I will probably have the stainless installed as well, just because the 6" stainless liner is super easy to clean with a 6" brush.

Thanks.

 

[EbS-P]

How much does cost matter?

 

[stoveliker]

An insulated class A should be more durable than a brick or other stoney chimney. Your foundation issues may play up again with a heavy masonry chimney there. That won't be an issue with a class A.

In any case you need an insulated liner if you go masonry. This is because the outside of your chimney stone does not seem to have 1" clearance to combustibles in roof and wall.

I'd go class A. Simply a better system, even if uglier.
You could build a chase around it (with 2" clearance from the class A) and cover it with stone veneer for the same look but much less weight.

 

[EbS-P]

I vote class A inside a stone veneer chase/chimney. It settled once they tried to fix it be we’re not able to. Is building a larger footer the correct solution. Class/chase a could basically be self supporting. The cost is probably half that of a masonry.

 

[JJ3]

An insulated class A should be more durable than a brick or other stoney chimney. Your foundation issues may play up again with a heavy masonry chimney there. That won't be an issue with a class A.

In any case you need an insulated liner if you go masonry. This is because the outside of your chimney stone does not seem to have 1" clearance to combustibles in roof and wall.

I'd go class A. Simply a better system, even if uglier.
You could build a chase around it (with 2" clearance from the class A) and cover it with stone veneer for the same look but much less weight.

I'm going back with the cinderblock/rock construction -- it simply looks better than the Class A by itself.

The question is whether to use a clay flue inside the chimney or use a Class A pipe inside the chimney? I was hoping to get some other experiences on the life of the Class A.

My chimney inspector (and installer of liner systems) has recommended the clay flue based on recent observations that he is seeing with failures of Class A pipe in similar applications after about 10 years. And I have a neighbor a few houses down the road that told me Saturday, that he has to have his inside rock work removed that goes up to a 20 ft vaulted system, so that he can replace his Class A pipe replaced because inspection has revealed 2 holes in it (after he had a small fire last year).

 

[JJ3]

I vote class A inside a stone veneer chase/chimney. It settled once they tried to fix it be we’re not able to. Is building a larger footer the correct solution. Class/chase a could basically be self supporting. The cost is probably half that of a masonry.

Masonry ends up being about 35 - 40% more than going back with Class A only, if I cased the Class A, the price difference masonry is only 25% more (more cedar, more carpentry). Going back with Class A only, the cedar siding on that end of the house has to be replaced and the roofline has to be built out. I got it quoted both ways.

After they demo'd the old chimney we found that there was one foundation slab for the cinderblock core and separate footings were laid with rocks and cement for the rock -- and the rock footings were not attached to the cinderblock foundation. The cinderblock foundation has settled (over 40+ years). The foundation company put a lift under the front edge of the foundation 9 years ago before we bought it, but now I see that they were only putting the lift under the rock footing, not the entire foundation. There was no way for them to know that it wasn't a unified foundation.

 

[stoveliker]

Okay. But if you build a chase with rock veneer of the same dimensions as the old masonry chimey you don't need to worry about the look of class A nor about cedar siding. So I think that argument doesn't hold.

However, it's your place, so it's all good.

You can't put class A in clay.
Class A is chimney pipe that should be free, can't be in a masonry chimney.

In a masonry chimney, you need a flue, either clay or a stainless steel liner. I would certainly do the latter; it will hold up better, be easier to clean, *and you have to insulate your flue* per code and safety. That's hard (impossible?) to do with a clay liner.
Build the chimney however you want, but put a stainless steel insulated liner in. The stove will work better, the chimney will be safer, and insurance won't make a fuss in the small chance that the excrement hits the fan.

 

[bholler]

I'm going back with the cinderblock/rock construction -- it simply looks better than the Class A by itself.

The question is whether to use a clay flue inside the chimney or use a Class A pipe inside the chimney? I was hoping to get some other experiences on the life of the Class A.

My chimney inspector (and installer of liner systems) has recommended the clay flue based on recent observations that he is seeing with failures of Class A pipe in similar applications after about 10 years. And I have a neighbor a few houses down the road that told me Saturday, that he has to have his inside rock work removed that goes up to a 20 ft vaulted system, so that he can replace his Class A pipe replaced because inspection has revealed 2 holes in it (after he had a small fire last year).

Don't use either. Just put an insulated stainless liner inside the new chimney.

 

[Crab]

Don't use either. Just put an insulated stainless liner inside the new chimney.

100% agree. When building 30 years ago, I got talked into clay flue, totally regret it. Altho I didn't have to demo the outside of the chimney thankfully, I had a hell if a time demo-ing the loose fill and poorly laid clay tiles inside my brick chimney.. . I replaced the clay with an blanket insulated heavy flex 6" stainless liner(Armor Flex .016 ")....your house needs a nice masonry chimney but rule out the clay tiles. Snd if this hasn't been mentioned, you might want to increase the chimney height.