Will an Old Fireplace Insert Require Flue Liner?

Sizing

• A masonry chimney connected to an open fireplace usually has a 12-by-12-inch tile liner, but most inserts need an 8-inch round chimney to vent gases out before they cool down and cause problems with creosote. National codes require, as a minimum, that a connector pipe go from the flue collar outlet of the insert up through the damper, and into the first ceramic tile of the masonry chimney. It’s even safer to do a full reline all the way up to the top of the flue because it will provide a better draft that results in less creosote buildup.

Other Reasons

• There are other reasons to use a liner, besides a need to resize your flue. Corroded flues allow smoke and carbon monoxide to enter your house. If your flue is on an outside wall, it might not be able to draw air properly because it’s too cold. A new liner will address these issues and fix problems with condensation, too.

Liner Types

• Two types of liners can be installed in old chimneys: a stainless steel or aluminum liner or a cast-in-place liner. Stainless steel or aluminum liners are tested by Underwriters Laboratories, an independent product safety certification organization, and are safe to use when correctly installed. Stainless steel liners can be used with any type of insert, but aluminum liners are only designed for medium-efficiency gas inserts. Cast-in-place liners are made from a cement-like product that adds structural integrity to your chimney in addition to venting.

Methods

• Before you install a new liner, you need to have your chimney cleaned to remove soot and tar. Liners can be inserted in several different ways. Stainless steel pipes are lowered down from the top of the chimney. Insulating concrete is pumped in by a specialist contractor. Flexible metal liners can be lowered down or pulled up the flue. Which system you use will depend on your personal circumstances, but a certified chimney sweep can help advise you.