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Problem Chimney Photo Gallery

16 Common Problems with Chimneys

Chimney not tall enough- A chimney should be 3 feet tall where it exits the roof and must be 2 feet taller than any object within 10 feet. Check out the Problem Chimney Photo Gallery to see how one homeowner dealt with this issue himself! Warning: Do not try this at home.

Cracked Crown - If an expansion joint is not installed around the top of your flue where it meets the crown, cracking will occur due to the movement of the flue.

Cracked, flaking bricks, moss or mold present, missing mortar joints - These are all indicators of water intrusion.
moss and mold are attracted to moisture. A cracked crown will allow water to enter the brickwork. If water is allowed to freeze and thaw repeatedly, this will damage your bricks and your mortar joints. Water will mix with the acids in the flue and deteriorate your flue. An improperly installed chimney cap can contribute to this condition as well. Cracked bricks can also be caused by the shifting of the chimney footing, sudden occurance such as lightning or ground movement. Improper brick laying can also trap water. Cracked masonry can allow oxygen to enter your flue, creating higher temperatures and could contribute to a chimney fire. All of these issues can be caused by improper chimney construction.

No Wythe between flues - A wythe is a solid wall of separation between flues plus a half inch air space. If the is no wythe and one flue fails, it can cause damage to the other flue. Flues can crack each other due to normal expansion or from a chimney fire. A cracked flue can allow noxious flue gases to penetrate the other flue and enter your home.

Flue too small or too large for your appliance (fireplace, furnace, wood or pellet stove) - If the flue is improperly sized it can cause you to burn more fuel than you should. This is a waste of your money as it goes up your chimney in an unburned state. In order to burn efficiently, the flue must be sized correctly for the appliance to which it is serving. When you notice a vehicle on the road blowing black smoke, you take notice and know that something is wrong with that vehicle. Chimneys are the same, black smoke emanating from your chimney is wasted fuel. Smoke from your chimney should be clear or white.

Flue does not protrude above the crown of the chimney - Your flue must rise two inches above the crown in order to prevent rain and snow from funnelling into your chimney. Rainwater mixes with the acids and deteriorates the flue, this will contribute to reduced fuel efficiency, reduced longevity of your appliance and will cost you money.

Missing refractory joints - Your ceramic chimney liner is comprised of sections, called "tiles". These tiles must be evenly stacked upon one another and bonded together using "refractory cement", not mortar. If mortar is used, it will fail because mortar is not designed to withstand heat. These seams or "joints" must be smooth on the inside. If they are not smooth, they will interfere with the operation of your chimney. If the joints are missing, they can allow poisonous flue gases into your home.

Chimney is in contact with combustible material - Your chimney must not touch wood. Any wood, anywhere. The code states there must be two inches of clearance from any wood inside your home and one inch of clearance from any wood on the exterior. This includes underneath your fireplace as well. No floor joists or walls can have any contact with the masonry whatsoever. There must not be any type of materials at all within these clearance areas, not even insulation. Sometimes, you will find plywood used under a hearth or within a chimney, this is an extremely hazardous situation. Woodstove piping too close to a wall or mantle is a major cause of fires.

Joints in firebox are too wide - Inside your fireplace there are firebricks. They must be assembled using the correct spacing from each other. If the joints are too wide or are constructed using the wrong type of bonding material, they will crack. Firebrick joints are not capable of withstanding heat like your firebricks are, they need to be the correct width in order to minimize cracking. Wide joints are also more susceptible to acid deterioration.

Corbelling in Smoke Chamber - Up inside your fireplace is the throat, it curves up and gets narrow. This should be a smooth transition. You should not see "stepping over" of the bricks. This causes increased turbulence of the smoke which promotes acid buildup and poor fuel efficiency.

Fireplace Face is cracked - If the contractor did not allow for expansion and contraction of the chimney, it will crack the face of the fireplace. This could allow for products of combustion (fire, poisonous gases) to leak into the living space of your home.

Appliance piping too close to combusibles - There must be 18" of clearance from all woodstove pipes unless proper shielding is installed. There must be 9" of clearance for furnace piping, or less if listed shielding is installed.

One flue for two or more appliances - Solid fuel appliances cannot be vented into same chimney as oil fired appliances. Example, a woodstove cannot be vented into the same flue as your furnace. There are exceptions to this rule, but all installations must be made per manufacturer's specifications.

Cracking around appliance piping - Finding cracks around your furnace or woodstove thimbles means there was no allowance made for the expansion of the pipe. This could allow for products of combustion (fire, poisonous gases) to leak into the living space of your home.

Outer Hearth area too small - directly in front of your fireplace is the hearth. It is considered a safety area in case hot embers or logs roll out of the fireplace. For small fireplaces (under a 6' square opening) you must have 16 inches of hearth extending out in front and 8"out to the sides. For larger fireplaces, you must have 20 inches of hearth projecting and 12 inches to the sides of the fireplace.

Chimney built with hollow blocks - Cement blocks used for chimney construction must be solid blocks or the hollows must be filled.