Thread: Voids within the chimney

I've looked up at many chimney interiors.
First time seeing the voids between the flue and the chimney walls. Thought the picture might generate some interest. The two bars are reinforcing steel (as far as I could tell) embedded into the chimney stucture to hold up the first of the flue liner tiles. The voids can be seen at both sides of the flue tile. I could not determine how high up the voids go, but it was several feet, and maybe the entire way up. Level 2?

So, what do the codes and NFPA 211 say about supporting the first flue tile?
Is rebar an approved flue liner material?
Is inserting any kind of reinforcing steel into a flue joint approved?
Does a smoke chamber or flue liner have to be intact and continuous?
Is this suitable for the class of service?
What are the sequelae from continued operation as is?

FYI-these are rhetorical questions for me. I want to see you dig for these answers.

Bob, you are way ahead of me in knowledge of these systems.
I told them that there should be no voids - as the heat from a fire will transfer through the common brick to the wood framed construction, and that the tile flue liners were not properly supported. I recommended a Level II inspection from a CSIA pro (should it be a level III?). We are generalists and know when to call in the big guns. Thanks for your enlightening comments and/or rhetorical questions. I cant answer them all but methinks there is danger out there. As far as any resulting consequences, that yes, an improperly constructed fireplace is subject to ignition where you don't want ignition - house framing.

The house is 60 years old. Brick exterior had no cracks or damage, nothing observable inside the firebox such as cracks or separation....but that flue tile construction got my attention. Flue tiles resting on rebar for support brought up the notion that this aint right. Rebar had unknown area of support (wrong regardless); will help the heat transfer to other areas (wood framing); block the flow of flue gases by diminishing the cross section of the opening; and just plain looks wrong.
Thanks again for checking in with me - Chris

Originally Posted by Chris Weekly

Bob, you are way ahead of me in knowledge of these systems.
I told them that there should be no voids - as the heat from a fire will transfer through the common brick to the wood framed construction, and that the tile flue liners were not properly supported. I recommended a Level II inspection from a CSIA pro (should it be a level III?). We are generalists and know when to call in the big guns. Thanks for your enlightening comments and/or rhetorical questions. I cant answer them all but methinks there is danger out there. As far as any resulting consequences, that yes, an improperly constructed fireplace is subject to ignition where you don't want ignition - house framing.

The house is 60 years old. Brick exterior had no cracks or damage, nothing observable inside the firebox such as cracks or separation....but that flue tile construction got my attention. Flue tiles resting on rebar for support brought up the notion that this aint right. Rebar had unknown area of support (wrong regardless); will help the heat transfer to other areas (wood framing); block the flow of flue gases by diminishing the cross section of the opening; and just plain looks wrong.
Thanks again for checking in with me - Chris

Chris, you are correct. This needs an assessment from a CSIA Certified Chimney Sweep. Not only will they be able to provide you with a proper inspection but it is likely that they will be able to correct those deficiencies. Just like you would recommend any other specialist like a electrician, plumber, etc.

Ashley Eldridge
CSIA Director of Education
Chimney Safety Institute of America (CSIA) | Plainfield, IN

Thanks for the affirmation Ashley. How would that flue tile be suported? I wonder - because there is no nearby structure for support as the smoke chamber slopes outward away from the flue. Just wondering - I'm not asking for a design for this - but it looks awkward from a standpoint of repair. Ya think it could be done easily enough?

Originally Posted by Chris Weekly

Thanks for the affirmation Ashley. How would that flue tile be suported? I wonder - because there is no nearby structure for support as the smoke chamber slopes outward away from the flue. Just wondering - I'm not asking for a design for this - but it looks awkward from a standpoint of repair. Ya think it could be done easily enough?

Chris;
The proper support would come from corbelled brick, just as you would expect from new construction. If the liners were to be removed a base plate could be used for the new, listed liner. It would, no doubt, be awkward, and quite possibly impossible to leave those tiles in place. I suspect there is more wrong than the picture shows. That is the logic for requiring a full level 2 inspection.

Ashley Eldridge
CSIA Director of Education
Chimney Safety Institute of America (CSIA) | Plainfield, IN