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Lining Your Fireplace Insert Flue

Wood Inset Chimney Liner Diagram

" Where a wood-burning fireplace insert is vented
into a chimney with an oversized flue, into an
unlined chimney, or into a chimney with a damaged
masonry liner, the chimney shall be refitted with a
properly sized UL Listed metal or masonry liner."

-WABO Codebook (From NFPA 211)


Q: We're about to buy a new wood-burning fireplace insert, and our local dealer refuses to install it unless we buy a stainless steel liner that goes all the way out the top of the chimney. Do we really need to do this? If so, is it something we can do ourselves?

Sweepy  You're required to reline a chimney for a woodstove or wood insert if the existing flue is oversized, unlined, or has a cracked or damaged liner. The big issue with fireplace insert installations is flue oversizing: most fireplace flues are WAY too big to efficiently vent the exhaust coming out of the 6" or 8" flue collars on today's inserts. Installing the liner eliminates flue oversizing violation, ensures the best possible insert performance, and eliminates the need to pull the insert out of the fireplace every time you clean the chimney. The job doesn't really require much mechanical aptitude, and many of our online customers choose to do it themselves.

Our Forever Flex liner kit for fireplace insert installations consists of a rain cap, a top sealer plate, a caulk tube of silicone sealant, a length of flexible stainless steel pipe and an adapter to allow attachment of the flex to the flue collar on the insert. For pricing, click here.


Chimney Liner Rain Cap
Rain Cap
To install our fireplace insert chimney liner kit, you'll need:
*work gloves (the edges of the stainless parts are SHARP)
*a cutting torch, offset grinder or sawzall to enlarge your fireplace's damper opening.
*a caulking gun to apply the silicone sealant
*sheet metal shears to trim off the excess stainless flex
*a standard screwdriver to tighten the draw bands on the flue collar connector, top plate and rain cap
Chimney Liner Top Plate
Top Plate
First, you need to remove the fireplace damper assembly or cut a 7" hole in it with a sawzall, offset grinder or cutting torch so the 6" flex pipe can pass through.
Chimney Liner Length
Flex Pipe
Slide the insert into the fireplace without attaching the surround panels, and carry all liner parts up onto the roof. Attach the flue collar connector to the bottom of the stainless flex pipe by tightening the draw band with a screwdriver, and lower this assembly down the chimney. Have your partner down below plug the flue collar connector into the flue collar on the insert and tighten the draw band.

Cut the excess flex pipe off at the top with sheet metal shears, leaving 4" protruding above the chimney crown or liner tile. Place the top plate assembly over the protruding flex pipe and affix it to the chimney top or flue tile with high-temp silicone sealant. Tighten the top plate's draw band around the flex pipe. Fit the rain cap over the stand-up collar on the top plate and tighten the cap's draw band.

Chimney Liner Flue Collar Connector
Flue Collar Connector
Down below, slide the insert forward a bit (the flex will allow some movement on the hearth), attach the surround panels, and push the insert back until the panels touch the fireplace facia.

Can't fit your arms in to make the connection? Click Here!


Note: Each Code Authority chooses the standards that regulate appliance and chimney installation and usage in their jurisdiction, and may modify code specs as desired. The above-referenced specification is from the Washington Association of Building Officials Woodstove Installation Code Book, and may not reflect the code requirements in your area. Contact your Code Authority for local regulations.

Manufacturers who submit an appliance to a recognized laboratory for safety testing may receive a specific listing for that appliance which may be accepted by your Code Authority in lieu of the standard code requirements. These listings are unique to each model, and can be found in the appliance's installation manual.


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