To function properly, there are three keys to any fireplace and chimney: proper design, proper installation, and regular maintenance and cleaning. A deficiency in any of these can result in poor performance or property damage and represents a safety risk to occupants of the property.
Conventional fireplaces include a firebox and hearth, where the fire occurs, and a flue through which combustion gases escape upward and out the top of the chimney. Common flue materials include unlined masonry, clay liners, and stainless-steel, which can be insulated or uninsulated. Additional components include a damper and flue cap, which are designed to control venting of the fireplace and to stop debris and excess moisture from entering the flue.
Fireplaces are designed to withstand the heat of fires but can be damaged by excessively hot fires (“Over Fire”), from burning too much material or from burning inappropriate materials. Chimneys are designed for the heat of smoke but are not designed to withstand direct exposure to fire and can be damaged if a fire extends into or develops within them. Igniting of excess creosote within a chimney flue is a common source of such chimney fires. Creasote is a byproduct of the incomplete combustion of materials, and most commonly develops in wood burning fireplaces. Chimney fires can result in cracked flue liners and masonry as well as discolored and damaged metal caps and fireplace components. Left un-repaired, cracks in a flue can result in combustion gasses leaking into the residence, presenting a life safety risk.
Water intrusion through cracks or openings in the masonry of a chimney can result in premature deterioration of the chimney and fireplace. Moisture can cause cracks, spalling, staining, and moss or fungal growth on masonry components. Such water intrusion can result from improper forming of a chimney crown, a lack of a chimney cap, and from deferred maintenance of mortar joints. Moisture intrusion can also result in costly, gradual, and long-term corrosion to metal components of fireplaces, including dampers and lintels.
Chimneys and fireplaces, which are located on exterior walls of residences, are commonly supported on foundations that are outboard of the main foundation of the residence and can be damaged as a result of differential settlement between the main foundation of the residence and the fireplace foundation. Settlement of a foundation can cause leaning and cracking of the masonry of a chimney, allowing water intrusion.
If damage to a chimney is suspected or observed, the first step for the property owner or manager is to reach out to an experienced forensic expert to determine the cause(s) of the damage.In some instances, a chimney or fireplace may have been damaged as a result of more than a single cause. For example, a chimney that has experienced long-term weather-related deterioration due to poor construction or poor maintenance may also experience a fire, resulting in additional damage to these components.