Do I need a chimney liner?

I am writing this, not to give a blanket statement, but to let homeowners know the facts about steel liners.

Last year, we received hundreds of calls from people requesting quotes to install a steel liner in their chimney. In many cases, these customers were told that a steel liner was required for their site-built, brick fireplace.

Let me be clear; steel liners are expensive. And in this case, most of the time, are NOT needed.

Brick fireplaces are, 99% of the time, part of the original construction of a home. They would, theoretically, have been constructed in compliance with the building code of the time, and, for at least some of their age, did not constitute a fire hazard.

Chimneys should be lined. The National Fire Code states that a liner can be built of brick, clay or steel. Most homes built in the past 50 years have a clay liner for a wood-burning appliance. Older ones may have clay or brick. These are usually 8 inches by 8 inches or 8 inches by 12 inches. That’s 64 to 96 square inches. This is an acceptable area to draft your fireplace. Now, if I stick a round liner down the chimney (I can fit a maximum diameter of 6 or maybe 7 inches through your 8 inch wide flue), I’ve just cut your draft area in half (if we remember our high school geometry). You now have to have small fires unless you want smoke coming back in the house. In addition to this, with a steel liner, sometimes you have to spend 5 or 10 minutes warming your flue before you light your fire.

Why would someone have told you that you need a liner if you don’t? Well, the fire code requires that a chimney be repaired or replaced if it constitutes a fire hazard. An inspector could identify a hairline crack in a clay tile liner and simply say, “You now need a $2000 to $3000 steel liner.” This seems to most commonly occur if his company happens to also install these liners. If you understand that you have one or two layers of bricks and an inch of clay separating the chimney gases from your home, then, unless your flue is severely damaged, you probably don’t need a new liner. You may need a little patch-up.

These are the most common times we would recommend a steel liner;
a) If you have or are installing a wood-burning insert inside of your fireplace (these must have a steel liner) or a free-standing wood stove where the manufacturer instructions require a steel liner.
b) If you have smoke coming back into the house from the chimney somewhere above the fireplace. In this case, we would first make sure that this is actually passing through the masonry and is not being vented out of the chimney and then coming back into the house through a vent or similar.
c) If you have had a chimney fire that was not resolved rapidly and thereby caused extensive damage to your chimney interior.

Chimneys have been built of brick, clay and mortar for over a thousand years. If you get them cleaned and inspected annually by a professional, you’re good to go. In my world, logic and common sense are senior to sales pitches. If someone told you that you need a liner, the thing to do is get a second opinion. Our standard annual service includes a full cleaning and inspection and we’ll give you the straight scoop.

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