Chimneys, Inside and Out

Whether it is an extension of a fireplace or a furnace, you should have your chimney cleaned or "swept" at least once a year, for several reasons.

 First, creosote often adheres to the inside of the fireplace chimney. Because of its chemical nature, creosote can actually ignite, rapidly causing a chimney fire and potential damage to the rest of the home.

Burning wood at a relatively low temperature (your cooking stove flame is actually hotter than a fireplace) causes incomplete combustion of the oils found naturally in the wood. When the smoke from a fire rises into a chimney, the residual chemicals may stick to the inside of the chimney liner. This residue becomes creosote.

Second, soot and dust build-up can clog a chimney and diminish heat output. A furnace flue may accumulate a layer of sulfuric acid or chlorine, which can cause erosion and big problems down the road.

A good rule of thumb is to not ever assume your chimney is functioning properly, even if you rarely use it. Animals, leaves and moisture from a buildup of snow or rain need to be taken care of before safe use of your fireplace.

A thorough check for any shifting of the chimnye that may have occurred over the years is also recommended. Years ago, chimneys were built with a section near the top made of terracotta, over time, these sections sometime move, causing the potential for leaks of carbon monoxide through the seams and even a backdraft.

In addition to a good cleaning, chimney inspection includes checking for leaks in the flashing around the chimney, which can cause wood rot and condensation. This, in turn, can damage electrical wiring and present a fire hazard.

by  Joseph Coupal

2-in-10: A Rule for Chimneys (and Big Brothers)

Chimney Code De-coded

Nothing says you can't add onto your home near the fireplace, bringing the exterior chimney brick inside. My oldest brother Kyle recently did just that when he walled-in his patio as a TV room, and I must say, it looks fantastic. A little bit of runaway ivy had to be peeled back from the brick chimney facade and clipped off, and he had to repair a few spots where the tenacious vines had attached to the mortar, crumbling it like a stale cookie, but with a few hours of labor and a little fireplace paint, Kyle made the backside of his chimney look like any other interior brick wall. Well, he had a little help from his kid brother, but we won't go there today...

All things considered, Kyle's addition was a pretty simple construction project, once we took into account certain fireplace and chimney construction principles. Specifically, I'm talking about the 2-in-10 rule, which dictates how high your chimney flue needs to extend in relation to other structures. Kyle wanted a super-high ceiling in his new room, until I told him what a bad idea that was. He was reluctant to listen at first, but once I threw him in a headlock, wrestled the blueprints out of his fist and explained a few basic rules of physics he finally bowed to my expertize.

The 2-in10 rule simply cannot be ignored.

In fact, I've been thinking about this basic tenant of home construction since I read this article this morning in the Seattle Times, which I thought I'd pass it along to those of you considering adding on to your house, or to anyone having mysterious fireplace draft problems, especially if you've recently done any construction in the vicinity of your chimney. It's fireplace 101, obviously, but it never hurts to have a little refresher course. In the end, it can save you not only a big headache but a lot of money.

As home inspector and columnist Dwight Barnett rightly points out, drafty fireplaces can often be traced back to flue height. More specifically, a fireplace draft frequently results from the height of the flue relative to other structures abutting, adjacent to or even in the vicinity of the chimney. To summarize, the chimney needs to rise at least 3 feet above the connecting roof, and at least 2 feet above any other structure within a 10-foot radius. If your chimney doesn't adhere to these basic rules, you're going to get drafts, resulting most often in smoke coming into the living area.

If you've already added onto your house in the vicinity of your chimney and have since been experiencing draft problems when you burn your fireplace, you need to measure. And if you discover you don't meet the rules spelled out above, you either need to extend your flue or extend the entire chimney. Meanwhile, if you're still just thinking about a home addition, you need to consider the 2-in-10 rule before you draw up your plans.

Alternately, if your kid brother happens to be a fireplace enthusiast who spent over thirty years in the fireplace industry, you could also just call him....right, Kyle?