By Johnathan Mason, Ace Chimney Service.
Sliding a wood stove or insert into an existing masonry fireplace is one of the most popular heating upgrades in Prairie Grove, and one of the easiest to get wrong. The stove is usually fine. The chimney above it is the part that decides whether the installation works.
The core problem: a big flue on a small appliance
An open fireplace throws enormous volumes of hot air up a wide flue. A modern wood stove is far more efficient, which means it sends much less heat up the chimney. Put that low-temperature exhaust into a flue sized for an open fireplace and the gases cool on the way up, slow down, and condense on the tile walls. The result is a sluggish draft, smoke at the door, and creosote building far faster than it should.
Why a liner is not optional
The fix is a correctly sized stainless liner running from the stove collar all the way to the top of the chimney, insulated where required. It matches the flue to the appliance, keeps the exhaust hot, and gives you a continuous, sealed path with no leaks into the old masonry. Most manufacturers require it, and it is the difference between a stove that drafts on the first match and one you fight all winter. Our chimney relining page covers the materials and the process.
Matching the size
The general rule is simple: follow the stove manufacturer’s listed flue size. A stove with a six-inch collar wants a six-inch liner. Going larger to “help it breathe” does the opposite. Going smaller chokes it. Where things get judgment-based is total height, offsets, and whether the existing masonry can physically accept the liner — which is why the flue gets measured before anything is ordered, not after.
The block-off plate nobody mentions
When a liner runs up through an old fireplace, the space around it inside the damper area should be sealed with a block-off plate. Without one, room air escapes up the void around the liner and cold air drops back down when the stove is idle. It is an inexpensive detail that has an outsized effect on how warm the room stays.
Get the chimney checked first
Before any of this, the existing chimney needs a real look: crown condition, tile condition, clearances, and whether the structure is sound enough to carry a liner. Finding a cracked crown after the stove is installed is a bad sequence. We inspect first, tell you what we find, and give you the price up front. Ace Chimney Service is insured and bonded, has 29 years in this trade, and covers Crystal Lake and McHenry County seven days a week from 7 AM to 7 PM. Call (815) 320-0883 or see pricing.
Frequently asked questions
Can I use my fireplace flue for a wood stove without a liner?
In almost all cases no. The flue is far too large for the appliance, and most stove manufacturers and installation standards require a properly sized liner.
What size liner does my stove need?
Whatever the manufacturer lists, which is usually the diameter of the stove’s flue collar. Bigger is not better here.
Does the liner need insulation?
Often yes, especially on exterior chimneys. Insulation keeps exhaust temperature up, which improves draft and slows creosote.
What is a block-off plate?
A sealed panel that closes the space around the liner at the damper, stopping heated room air from escaping into the chimney void.
Will a stove insert heat more than my open fireplace?
Substantially. An open fireplace loses most of its heat up the flue; a closed appliance keeps it in the room.
How often does a stove liner need sweeping?
At least annually, and more often if you burn a lot or burn wood that is not fully seasoned.
Can an old chimney be too damaged to reline?
Occasionally. If the structure is unstable it needs repair first, which the inspection will tell you.
Should the liner run the full height?
Yes. A continuous run from the appliance to the top is the whole point — partial liners leave the problem in place.
Published September 1, 2026