Your chimney and all of its related components make up a complex system that is subjected to many years of harsh operating conditions. Extreme temperature fluctuations inside the flue, deposition of corrosive compounds on the flue or liner walls, effects of weather on the outside of the chimney, and eventual deterioration of construction materials all combine to make it inevitable that chimney liner problems occur over time. With proper installation and maintenance, you can minimize the costs of chimney liner problems.
Chimneys in homes built before the 1940s are likely to have been constructed with no liner inside the flue other than the bricks and mortar that make up the chimney itself. While a well built masonry chimney will last many years without problems, the effects of age, weathering, and foundation settling will eventually make the chimney leak. An unlined chimney will eventually need to have a chimney liner installed inside it to improve building safety and enhance the performance of the fireplace or other appliances connected to the chimney.
New homes with masonry chimneys are likely to have clay tile liners inside the flues. These liners will give decades of good service, but they are also subject to deterioration over time. An annual inspection will reveal whether cracked tiles or corroded mortar will make it necessary to repair the liner or insert a flexible steel liner to replace it.
If a metal liner is properly sized and fitted into a chimney and if it is made of the proper materials, it will also last many years without requiring repair or replacement. However, a metal liner that is not made of the proper alloy for its intended use may develop leaks due to corrosion caused by ineffectively exhausted combustion gases.
High efficiency natural gas and oil fired furnaces vent combustion gases at relatively low temperatures, which will condense inside the chimney liner as water and other products of combustion. These compounds will cause corrosion if the chimney liner is made of aluminum or the incorrect stainless steel alloy. Before you install a new fuel burning appliance to be vented through your chimney, you should always consult with a chimney professional and the appliance manufacturer’s specification sheets to be sure your chimney liner is adequate for the new application.
An improperly installed chimney liner will deteriorate faster than one that is installed correctly. Badly sealed joints will leak. Improperly insulated liners will have more creosote accumulation than properly insulated liners, requiring more frequent cleaning and subjecting the liner materials to greater wear and more corrosive conditions.
External weather and environmental conditions can also contribute to chimney liner problems. A high quality screened chimney cap or a top-seal chimney damper can keep precipitation from running inside your chimney liner and it will keep moisture from seeping into the top bricks and masonry cap on your chimney. It will also prevent leaves, other trash and small animals from cluttering up the inside of your chimney liner.
By keeping moisture out and cleaning your chimney liner regularly, you will avoid or delay many of the problems that might occur if you neglect these critical aspects of chimney maintenance. A properly designed, installed and maintained chimney liner will keep your home safer and more energy efficient for many years without requiring expensive repairs or replacement.