Masonry chimneys are freestanding units that carry exhaust gases out of the house. To prevent superheated gases from escaping, chimneys should be tile lined and free from cracks or gaps, or they should have insulated stainless-steel flues. Annual inspections and maintenance are crucial to chimney health: If you discover mortar or flue tiles that are cracked or missing, the chimney is unsafe. Chimney flashing and roof safety are further discussed in Chapter 5.
These days, new and retrofit chimneys are often nonmasonry. There are several reasons for this transition: building code and insurance requirements; a shrinking pool of qualified masons; the inherent inflexibility and tendency of masonry to crack and compromise safety when structurally stressed; and, perhaps most important, a host of safe, cost-effective, and easily installed insulated metal chimneys now available. That noted, the review here is limited to masonry chimneys.
Chimneys and their flues should be inspected at least once a year and cleaned as needed—ideally, before the heating season. Better chimney-cleaning services will get up on the roof, inspect the chimney top, and in some cases lower a videocamera into the flue linings. That video is very helpful if the chimney needs relining because homeowners can see the damage for themselves and make an informed decision.
Because chimney cleaning takes serious elbow grease, working atop the roof is often the most effective way to brush clean a chimney. But working on a roof is inherently dangerous to you and your roof shingles, which can be easily abraded, torn, and dislodged, leading to leaks. Moreover, because many people put off cleaning a chimney till it’s almost heating season, they frequently go aloft when the weather is inclement or the roofs are slick after a rain. For all these reasons, you’re probably better off hiring an insured professional, certified for cleaning and inspecting.
However, if you are determined to clean the flues yourself, first turn off the furnace and other appliances (such as water heaters) that vent to the flues and disconnect their vent pipes. Using duct tape, tape plastic over the thimbles that open into living spaces, to prevent dislodged soot from entering. If you have a fireplace, open its damper to allow dislodged soot to fall into the fire pit. Then firmly tape sheet plastic around the fireplace opening. But before you start, suit up. Dislodged creosote and soot are highly carcinogenic, so wear a respirator mask with replaceable cartridges, tight-fitting goggles, gloves, and disposable coveralls.
To clean a chimney thoroughly, you’ll need special brushes, which scrub flue surfaces without damaging them. Today, many professional sweeps favor polypropylene brushes to clean sooty flues and stiff steel-wire brushes for flues with heavy use and creosote buildup. These brushes come in various sizes to match the most common flue cross sections. You can screw them onto a series of 3-ft. to 4-ft. rod sections or to a continuous flexible rod (on a reel) up to 50 ft. long.
