Flue Lining Question + Stove Reco

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New Member
Oct 19, 2023

Two related questions for you all:

1) I have a chimney that was formerly used for a gas boiler, which I'd like to line and use with a wood stove I'd install.

Flue is lined in galvanized steel I think(?) currently. Starts off at 9" in the boiler room, ends with a 7" top on the roof about 35' above the ground (3 floor townhouse).

I'd like to avoid removing this existing liner if I can, just to reduce the risk of damaging the masonry and such as I do so.

It seems like a 5.5" ID/6.75" OD insulated zero-clerance liner is the biggest I could possibly get down that flue--agree? I'm assuming I should do a zero-clearance because I can't verify the clearance between combustables and the masonry given the house was built in 1875?

2) ...and then if I install a 5.5" ID liner, thoughts on using a 6" flue stove? I understand you can trade diameter for height in some cases. Would a chimney ~35' tall qualify?

TIA--and if anyone knows any good chimney/stove folks in the Philly area, happy to consult with them, just having trouble finding anyone local to figure this out with me.
Yes, a zero-clearance liner is needed. What is the ID of the masonry chimney? 35'+ is a very tall flue system. 5.5" may be helpful in reducing the draft strength a bit. A wood stove will likely need a draft damper on the stovepipe to further reduce draft strength.
Thanks for your quick reply--great question. I can only see the liner, so unclear, but my guess is ~8-9". There's an unused, unlined flue next to the one we're discussing here that is 9" (square) in the basement.