Chimney liner (chemisage de cheminée): what it is, how serious, what it costs

A brick chimney is not made to be in direct contact with hot smoke, soot and condensation. The liner, « chemisage » in a French report, is the pipe set inside it, most often stainless steel. It carries the smoke from a wood stove, or the gases from an oil or gas furnace, up to the top, and it protects the masonry.

In older chimneys, the flue is sometimes made of clay tiles, which can crack. When an appliance changes, a new wood stove or a gas furnace replacing oil for example, a liner suited to the new appliance is often needed.

It is a safety matter, against fire and against carbon monoxide. A cracked liner, one clogged with creosote or one that does not suit the appliance can let heat, sparks or gases into the house. Creosote is the tar-like deposit wood smoke leaves behind: it can catch fire inside the flue.

The home inspector cannot see inside the chimney. When the inspector asks for it to be inspected and swept by a specialist before the deadline, I generally put it under “Fix first”: you need the answer before lifting the inspection condition, especially if you plan to heat with wood.

Having the flue inspected and swept by a chimney sweep: $300 to $650. If the chimney is no longer used, closing it off and sealing it properly: $350 to $900. Redoing the joints and the crown, the concrete top that caps the chimney: $900 to $2,500.

Installing a new liner depends on the chimney height, the diameter and the appliance: the chimney sweep or installer prices it after the inspection.

These are ballpark figures for Quebec, to be confirmed with quotes.

1. Could you see inside the flue, or only the outside of the chimney?
2. What appliances are connected to it: wood stove, fireplace, furnace, water heater?
3. Did you see soot, water marks or cracks around the chimney, in the basement or the attic?

Ask the seller for the latest sweeping invoice and, for a wood stove, the installation certificate: your insurer may ask for it.

Does your report mention the chimney? Upload it: in five minutes, I tell you what comes first, what to have checked and what to ask the seller.

For a wood-burning appliance used regularly, at least once a year, and more often if you burn a lot. Many municipalities have their own bylaw: check with yours.

Yes, at least closing it off properly, top and bottom, to keep out water, animals and drafts. An old flue closed with makeshift materials is something an inspector may flag.