All About Your Chimney Lining

Lining your Chimney

Why are so many people having their chimneys relined these days? As cold weather approaches and you fire up your heating system, wood stove or fireplace, are you thinking about the inside of your chimney system?  In a perfect world, the inside of a chimney is something you’d never have to think about. Unfortunately the world isn’t perfect and many masonry chimneys aren’t either! Let’s discuss what can go wrong inside of a chimney and how chimney liners figure into it.

A chimney’s purpose is to carry the flue gases out of the home, and it needs to do this without getting over-heated. The problems with the inside of chimneys falls into two general categories: the problems that cause flue gasses to back into a house (smoke or carbon monoxide) and the problems that can cause house fires.

Most masonry chimneys are lined with fireclay tiles. This material has been used for 100 years and was a huge improvement to unlined chimneys of the 1800’s and before. In fact they served well enough until the 1970’s. Here’s what happened.
chimney lining

As people became conscious of the cost of heating, they started to put glass doors on the front of their fireplaces. This changed the fuel-air ration that had existed for eons. Suddenly masonry fireplaces that had never had problems before got full of soot and creosote in a matter of months.

Fireplace inserts caused the same problems, only even more so. The stoves were engineered for flue openings of six or eight inches round but were venting into chimneys built for open fireplaces. And fuel-air ratio was now so low that many chimneys collected a thick, wet, gooey tar. In some cases, chimneys were catching on fire within weeks after the stoves were installed!

Obviously the same was true for freestanding woodstoves.

And what about central heat flues, that is gas and oil? Well, those appliances changed too: they became much more efficient. The problem there isn’t creosote, as these fuels burn much cleaner. But it takes a certain amount of heat loss in the chimney to take the fumes up the flue and it wasn’t there anymore.

Three bad things happened to the masonry chimneys:

  1. More heat was delivered into the home and the flues didn’t have enough heat to carry the gasses up and out!
  2. The water in the exhaust condensed in the flues (instead of in the atmosphere). The inside of gas heaters in particular got very wet. Very, very wet indeed: so wet that they could freeze in the winter and block up, or so wet the wall paper inside the house was peeling where the chimney passed by. So wet that the freezing and thawing deteriorated the outside bricks themselves!
  3. And carbon monoxide levels in the houses skyrocketed! Tens of thousands of people a year are affected by CO poisoning and many don’t even realize it. They just don’t feel so great; lethargic or as if they have a cold. And of course there are even deaths… it’s a bad situation.
    • For reasons more technical than this article will cover, a properly sized liner will extend the appliance life and its heating efficiency. This is true for both central heaters or wood burning appliances.
    • For gas flues you can use aluminum but it often doesn’t have a very long life with modern appliances. The best material for lining a chimney, whether gas, oil or solid fuel, is stainless steel. #316 is a very good alloy for chimney lining and is readily available.
    • The liner must be properly sized to the appliance for it to work properly. Either too big or too small is not good enough. Don’t get this wrong.
    • There are three systems in your home that can kill you: electrical, plumbing and venting.  Unless you really know what you’re doing, unless you’re the kind of do-it-yourselfer who’d dig up his own sewerage system etc. don’t try to do it yourself. While anybody who can work with tools can theoretically do anything, there are enough things to go wrong with a venting system that this isn’t something you should tackle yourself. Hire a professional.

    Add to this that in most cases tile chimneys are not particularly well sealed in the first place, just because that’s the way they’re built. Also, many homes now operated under “negative pressure.” That means that our airtight windows and doors, our weather stripping, and our fans in the house all conspire to prevent good draft in chimneys. All of these factors combine to create the need for smaller, positively sealed venting systems.

    This is where chimney liners come in. The info above pretty well describes why you need a modern chimney liner. Lining your chimney with a good stainless steel liner will pay you and your family dividends both in dollars and in vastly increased safety.  Make it your next home improvement!

3 thoughts on "All About Your Chimney Lining"

Tasha says:

First, your fire place should be inpeectsd prior to lighting any fires. The flue should be cleaned of all creosote and to be sure no critters have nested in the flue if there was no chimney cap atop the chimney. Inspection is very important to protect the house from catching fire. After you are certain the chimney is safe, do a draft test. Open the damper. Roll up a newspaper, not too tightly. Light the paper on fire and hold in the firebox like a torch. This should cause an upward draft and show you that the chimney properly vents up the flue. Now you are ready for a real log fire.After the inspection and draft test is complete, you are ready to begin. First, make sure there is a metal grate in the firebox. This is a raised metal grate which keeps the logs off of the floor of the firebox. On the metal grate, place a generous layer of crumpled up newspaper. On top of that, cris cross about small 8 to 10 branches (kindling). Then, add a layer of small logs. Light the fire by catching the paper on fire. The kindling will begin to burn. Without disturbing the fire too much, gently place larger logs on the burning kindling by allowing some air space between the logs for the flames to come up and lick the logs to catch them on fire. Then add more logs going in the other direction. Or, you can cheat and get a fire log at the grocery store for about $4.00. All you do is place the fake log, still in the wrapper on the grate inside the fire box and light the corners of the outer wrapper and you have an instant fire for three hours. Do not touch the log because it will fall apart and not burn as long as it should. I sometimes save an empty paper milk carton to use as a fire starter because those cartons have a layer of wax on them and they burn really hot and make a great addition to starting a speedy fire.Always have a fire place poker so you can move the burning logs as you add more logs to the fire.You always have to think of safety first. Never begin a fire unless you have a fire extinguisher in the house. Move stored logs away from the fire. Do not have a rug up against the hearth. Use common sense. Have a fireplace screen so it catches hot embers from poping logs.If you can find pine cones that have been dipped in copper sulfate, they make a fire turn really pretty shades of blue and orange.I am not a pyro, but I have been using wood stoves and a fireplaces for more years than I care to admit here.References :

[…] All About Your Chimney Lining – High’s Chimney Service Inc. […]

[…] Flue – this is the empty space inside your chimney that allows combustion gases to vent. 3. Flue Lining – For a safe flue, a lining must be used to ensure minimal accumulation of flammable debris. […]

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