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Chimney maintenance is critical to maintaining a safe home; however, most homeowners rarely, if ever, have their chimney, and the appliance(s) venting into it, professionally cleaned and serviced on a regular basis. Any chimney, whether used with a fireplace or a wood or pellet stove or simply for venting a heating system or water heater, can be damaged due to water entry or interior blockage. While this can include water damage into the structure, an even greater concern is that a blocked chimney can potentially increase the chance of a house fire and/or dangerous exhaust gases (such as carbon monoxide) filling the home.

The National Fire Protection Association (NFPA) and Chimney Safety Institute of America (CSIA) recommend a level 2 inspection of all chimneys for all real estate transactions. Home buyers would greatly benefit from knowing whether the chimney and the system(s) venting into the chimney are safe to use and are in functional condition. Plus, since chimney repairs can potentially be very expensive, knowing the condition of the chimney when the sales contract is still being negotiated can potentially save the home buyer a considerable amount of money.

A level 2 chimney inspection consists of cleaning the chimney’s interior, a detailed inspection of the chimney’s exterior and video or still photography of the chimney’s interior. Such an inspection is well outside the scope of a home inspection. Very little, if any, of the chimney’s interior is visible to a home inspector which is why this third party service is so important.

What is done as part of a home inspection?

In the course of a home inspection, the inspector will view the chimney from the exterior and inspect the visible portions of the fireplace from the interior. If a wood burning insert is installed, the home inspection is limited to the chimney’s exterior. Removing a wood burning insert or pellet stove is well outside the scope of a home inspection, and some of these older systems are not properly installed. The inspector is not performing a code inspection nor verifying that the unit was installed per manufacturer’s instructions. When an insert exists, the best bet is to consult a certified chimney professional. The chimney professional will remove the insert and ensure that the flue is properly attached and in satisfactory condition.

On the chimney’s exterior, the home inspector will look for visual damage to the chimney, such as cracks in the crown or missing mortar in the chimney’s sides. We also look at the chimney’s height. Generally there is a 3-10-2 rule for chimneys. This rule says that chimneys must penetrate the roof by at least 3 feet and must also be 2 feet taller than anything within 10 feet of the chimney. A chimney that terminates too short may not draft properly due to air currents affected by nearby roofing for example. Tree branches should also be kept trimmed away from chimneys.

Damage or cracks to the masonry can allow water in which can lead to much worse damage down the road. Loose bricks can also fall and damage the roof below or injure someone on the ground.

    This chimney had considerable mortar deterioration allowing me to literally remove bricks. This condition can also allow considerable water to infiltrate the chimney as well as allow bricks to possibly hit someone on the ground.

    This chimney has a damaged crown (aka mortar cap) as well as cracks in the chimney masonry.

While inspecting the chimney’s exterior, the flashing is also checked to help prevent roof leaks. Often a roof leak will occur where there is a penetration through the roof, such as at chimneys, vent stacks or skylights. Preventive maintenance is key to ensuring a dry home. Chimney and other roof flashings should be regularly checked and resealed as needed.

The condition of the interior flue liner is rarely if ever visible to the home inspector. Chimneys built before 1940 normally were not lined; however, a proper liner is often needed to safely vent a gas- or oil-fired appliance into the chimney. After many decades of gas or oil fired appliances venting into an unlined chimney, these unlined chimneys will likely show interior (hidden) deterioration by this point. Relining a chimney with stainless steel is possible yet quite expensive.

I also always recommend that a proper rain cap be installed at the top of the chimney to prevent debris, animals, rain water, etc. from entering the chimney. Each flue within the chimney should have a rain cap installed.

Within the firebox, the inspector will check for deteriorated masonry and ensure that the damper functions properly.

Hearth Extension — Often Overlooked

Besides the firebox itself, the inspector should ensure that the hearth extension (the area in front of the firebox) is properly sized. Many homes have insufficiently sized hearth extensions which can increase the chance of a house fire. When the firebox opening is less than 6 square feet in size, the hearth extension should extend at least 16 inches in front of and at least 8 inches beyond each side of the firebox opening. When the firebox opening is 6 square feet or larger, the hearth extension should extend at least 20 inches in front of and at least 12 inches beyond each side of the fireplace opening.

The hearth extension has several functions including helping to keep heat from the firebox away from combustible flooring such as carpet or wood. A log rolling out of the firebox or hot embers hitting carpeting or wood flooring could obviously start a house fire. A hearth extension should be non-combustible material such as tile, brick, concrete or stone.

    This hearth extension was only 14 inches deep and presents a potential house fire hazard. Multiple burn marks existed on the adjacent carpeting.

Only seasoned, dry wood should be used in wood burning fireplaces and stoves. Doing so helps limit the accumulation of creosote within the firebox, smoke chamber and flue. Creosote is a black tar-like substance from condensed flue gases and unburnt carbon that exists in firewood. With a hot-burning fire, this helps keep the flue gases and particles hot as they exit the chimney. A lower temperature fire allows this material to condense as it rises up the chimney and gets stuck there.

    This photo shows creosote accumulations in a flue and throat (the area above the firebox). The fireplace/chimney should be properly cleaned and inspected before further use. 

Homes with fireplaces, wood or pellet stoves, or any fossil fuel appliance (gas, oil, LP) or even an attached garage should have at least one carbon monoxide (CO) detector installed. Most carbon monoxide (CO) detectors should be replaced every 5-7 years although some newer CO detectors have a 10-year design life. Simply pressing the TEST button on a smoke or CO detector only tells you whether the unit is powered, it does not tell you that the sensor will function in an emergency. This is why regularly replacing smoke and CO detectors is critical for home safety.

Matthew Steger, ACI, WIN Home Inspection 

Facts, opinions and information expressed in the Closing Comments Blog represent the work of the author and are believed to be accurate, but are not guaranteed. The Lancaster County Association of Realtors® is not liable for any potential errors, omissions or outdated information. If errors are noted within a post, please notify the Association. Posts represent the author’s opinion and are not necessarily the opinion of the Association.

Lancaster County Association of Realtors®

Lancaster County Association of Realtors®