There are three different types of chimney liner commonly used.
Brick was used in the older homes built in the nineteenth and first half of the twentieth century. These bricks tend to deteriorate with age and moisture and should not be considered suitable for further use without a professional inspection annually.
Using a brick lined chimney for a gas or oil fired furnace or gas logs is a recipe for disaster. The chimney will probably have to be re-lined using stainless steel. The tops of older brick chimneys often have to be removed due to deterioration making them unstable and dangerous. The repair sometimes necessitates removal of the chimney down into the attic before a stable foundation on which to rebuild it is found.
Clay liners are the most common liner in use in today?s masonry chimneys. These liners resemble pipe made from a “flower pot”-like material. This type of chimney liner gives reasonably good service, over time the top liners tend to deteriorate from the affects of being exposed to extremes in weather, and will need replacement.
Any misuse of the fire place (burning papers) will crack the liners in a minute or less, so care needs to be exercised. Chimney fires usually crack the liners. (Cost of repair sometimes covered by homeowners insurance). Clay liners can be removed from the top down and replaced, without rebuilding the chimney.
Stainless Steel Liners
Stainless steel liners come in two forms, rigid and flexible. The rigid pipe is used predominantly in new home construction, and the flexible pipe is used for re-lining older chimneys. Stainless steel has a lifetime warranty (20 years). This type of pipe must be cleaned annually to remove soot and creosote, that if left in place will mix with water turning into an acid which eats away at the joints, destroying the pipe.
NOTE: Furnaces and gas hot water heaters that use plastic pipe for the flue are available and are an option where the chimney or flue pipes are unusable.
NOTE: An oil-burning furnace cannot be connected to the same chimney as a gas-burning appliance.