Cleaning your chimney
How to give cresosote the brush off
A chimney inspection is de rigueur before the first spring fire. Even if you cleaned it last fall, birds and other critters were waiting to move in as soon as you were out of sight.
If your chimney has a clean-out door or a removable elbow near the vertical section, you can inspect it from below. Just reach in with a mirror and angle it until you see a patch of sky at the top, lighting the insides of the flue.
If you can’t see up the chimney, you’ll have to climb on the roof and look down. Again, take the mirror and angle it to re-direct sunlight down the flue. It’s far more effective than a flashlight.
You’re looking for three things: obstructions, structural damage, and soot or creosote deposits. If you see fallen bricks, broken tiles, or split metal linings, call in a pro to repair the chimney. Nests and creosote call for a little DIY with brush and rods.
You’ll need a steel brush for a masonry flue and a softer plastic brush for metal linings. The brush should be of a size and shape to fit the liner snugly. And you’ll need enough extension rods to reach from the roof to the clean-out. A proper set of brush and rods costs about the same as a single visit from a chimney sweep. The cheap alternative, pulling a straw-stuffed feedbag up and down the flue with a rope, requires somebody below pulling on the dirty end, in which case flowers and apologies might also cost more than the brush and rods.Soot is loose and dusty and most of it will have already fallen. You’re also likely to encounter creosote, which is formed by condensation when hot exhausts hit the colder section of the chimney.
Creosote looks like tar when it first condenses and it can be runny enough to leak through stovepipe joints. But when it cools, it hardens into a shiny, black, highly flammable coating. Subsequent heating can puff it up into a crisp waffle that flakes away and falls to the clean-out, or it can set off a chimney fire. Crisp, shiny, or gooey, if you see more than three millimetres in the chimney, it’s time to sweep.
Close the clean-out, if there is one, or cover the fireplace with duct tape and plastic. Then, get back on the roof and push the brush in from the top, attaching the extension rods as you go. If you hit an obstruction such as a lodged nest, try to pull it up rather than pushing it down, which may cause it to jam.
When you’re done, clean up the mess below and light that first spring fire without further worry.
This article was originally published on March 15, 2002