The chimney is just about the last thing anyone thinks about when it comes time to do spring home maintenance, but a leaking chimney can cause expensive damage to the home so should be at the top of the priority list.
Chimneys can leak in several areas. The flashing is the most common site where water can leak inside the attic area and down walls where it can rot out wood and damage drywall and wallpaper. Flashing should be checked every spring. The way to do this is to look inside the attic area right after a hard rain. Look for water marks and wet areas on rafters and joists. Water can travel along rafters to different areas, so trace the water lines to the source. There may be more than one leaking area around chimneys and vents. If you are unable to check for flashing leaks after a rain, spray water on and around the chimney for several minutes, then check the interior of the house.
Flashing repair can be made if there are only small gaps in the flashing by applying clear silicone to the area to seal it up. Larger gaps, rusted flashing, or flashing with holes in it needs to be replaced by a professional who uses both J and Counter flashing and installs it correctly. Incorrectly installed flashing can cause leaks.
The mortar between the bricks can cause leaking if there are cracks, holes, or deteriorated areas in the mortar. Missing or shifted bricks which have broken bond with the mortar are another source of leaking.
The cement crown, which is a roof for the chimney, keeps damaging rain water out of the interior of the chimney chase. Cement crowns deteriorate and crack over time due to exposure to weather. Rain water, when mixed with creosote or acidic flue gasses from gas flues forms an acid which breaks down mortar. This can be dangerous if there are gaps in the flue liner because toxic gasses can escape the flue into the living space of the home. A badly cracked crown or expanded masonry can be an indication that a chimney fire occurred , even without the homeowner’s knowledge. To protect crowns, crown seal products are available which seal cracks and form an impenetrable coating. If the crown is in very poor condition it may need to be rebuilt.
Masonry water repellant products are available which are sprayed on the chimney to form a breathable barrier to water. Water is the number one cause of masonry chimney damage. If a chimney is spalling with the brick faces popping off it means that it is saturated with water. When the water freezes it expands, and the brick breaks. Unfortunately, many chimneys have been built with soft type bricks, which are more susceptible to moisture penetration than hard bricks. A good water repellant should be applied to all chimneys to extend their life.
Lack of a chimney cover allows rain water, birds, and animals to enter chimney flues. Simply installing a good heavy duty stainless steel chimney cover can save thousands of dollars in repair bills which can include relining flues, filling joints with a ceramic compound, repairing smoke chambers, repairing fireplaces, and replacing rusted dampers.
Wood chimneys serving manufactured fireplaces need to have a proper chase top with breaks that sheds off water. Without this important element, wood trim and siding can rot out and need to be replaced. A wood chimney needs to have the correct termination cap, storm collar, and flashing, and the collar and flashing needs to be sealed with silicone to prevent water entry into the chimney. Water inside manufactured chimneys can damage the fireplace, damper, or wood framing.
Chimneys should be inspected annually by a qualified professional chimney sweep. Some sweeps offer a leak diagnosis service, which includes checking all areas of the chimney that could cause leaking, a leak check with water, and a list of solutions. Certified Chimney Sweeps in the U.S. and Canada are listed at www.csia.org.