Why Rebuild with Brick
Okay, so I have a house with a dual flue clay liner brick chimney that hasnt been maintained by previous owners. Between the leaking cap on the first flue used for a wood burning fireplace, this flue also has a shifted clay section about 3 lenghts from the top so its OOS. The second services the boiler and hot water heater. It wasn't venting well when we bought the house, until I added a vent for make-up air. It does vent and have the proper pitch, I have checked at times with a proper meter from the firehouse, I would not keep using it if this hadn't corrected the natural vent.
The other issue is that it may have some settlement, it is an old style build where the hearth extends out supported but the floor joists instead of block to the footing. The foindation sits at about the face.of the firebox so the main weight is bearing as it should but the modern code is to have a full support.
The thing would need repointing but I think it is beyond that and it regularly spalls off big flakes of brick. I am sure if i lined it and poured around the liner that would add stiffness but I also was thinking that you dont see many brick chimneys on new builds and while I may not be a mason, I am a carpenter so am I out of my mind to consider ripping down the old brick to a point above the damper perhaps and then mounting the liner and boxing out a finish detail around.it. It seems like an ideal way for a lot of people to save when dealing with a masonry chimney that needs to be rebuild brick by brick but haven't seen it done before.
Even as a.hypothetical, is this not a viable idea? I would think a proper double lined stainless and a heat gap would make it easily safe enough or a layer of type x in the inside of all framing. I actually have a couple other more specific questions but figured I would start with proof of concept