DIY How to Replace a Rusted Chimney Flue

Remove the cap and top plate on your chimney top’s crown on your roof. Depending on the type of cap, it may have clips that you unhinge to remove the cap or it may be secured with screws that you will need to unscrew. Remove the top plate by sliding a steel spatula between the top plate and the chimney’s crown to separate the adhesive that secures it or unscrew the masonry screws that hold it in place. Lift the top plate up to remove it.

Put on gloves and then grasp the edge of the old flue liner and pull it straight up and out from the chimney. The liner may be very long, depending on the height of your chimney.

Slide the new liner into the top of the chimney’s opening. Twist and turn the liner to help move it down into the chimney. The liner will stop once it reaches the overhang inside the bottom of the chimney. There will be a length of liner out the top of the chimney; this is normal.

Put the top plate on the chimney, over the liner.

Draw a line on the liner where the top plate ends. Use tin snips or a handsaw to cut along the line.

Secure the top plate. Squirt a bead of silicone adhesive along the bottom side of the top plate's rim, or on the chimney top. Push down on the top plate to secure the top plate to the chimney top. If you prefer, you can also screw the top plate in place with masonry screws.

Replace the cap on the top of the chimney by screwing it back into place or by clipping the hinge clips.