Flue opening too small for chimney liner?

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New Member
Dec 28, 2023
Hi all, I'm interested in putting a Regency Ci2700 fireplace insert in to my existing masonry fireplace. Had the installers come out to take a look first and it turns out my flue opening is ~4" and evidently they need ~6" for the chimney liner. What are my options? Another vendor said that you can "chip out" some of the bricks to accommodate the chimney liner. Is this advisable? Thanks!
Where is the restriction? At the damper plate?
Yes, not a great picture, but here's the shot looking up at the damper.

The damper can be cut out or removed to clear the liner.
Thank you. Does this need to involve a masonry professional? The installer said this is not something they would undertake.
Find a different installer this is commonplace for insert installs.