submitted by Matt Halper, owner of American Chimney, www.americanchimney.net
The chimney is one of the most taken-for-granted parts of a home. Typically it tends to receive neither the attention nor the concern usually accorded other household service systems.
The fact that chimneys may do their job reasonably well, even when abused or neglected, contributes to this atmosphere of indifference. Chimneys are far from the passive black holes that most people assume them to be.
They perform several vital functions, and their simple appearance misrepresents their complex construction and performance requirements. A chimney deteriorated by constant exposure to the weather can be a potential safety hazard.
A masonry chimney is constructed of a variety of masonry and metal materials, including brick, mortar, concrete, concrete block, stone, flue tile, steel and cast iron.
All masonry chimneys contain combinations of, or possibly all of, these materials, most of which are adversely affected by direct contact with water or water penetration. All masonry chimney construction materials, except stone, will suffer accelerated deterioration as a result of prolonged contact with water.
Masonry materials deteriorate quickly when exposed to the freeze/thaw process, in which moisture that has penetrated the materials periodically freezes and expands causing undue stress. Water in the chimney also causes rust in steel and cast iron, weakening or destroying the metal parts.
Weather-damaged lining systems, flue obstructions and loose masonry materials all present a threat to residents. Regular chimney maintenance is essential to prevent damage, deterioration and future high-cost chimney repairs. (CSIA.org)