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Home Inspection: External chimney problems

By : John Martino | In : Home Inspections

A chimney must be water tight and gas tight to properly move the products of combustion to the exterior of the home. Chimneys do their work in a harsh environment. Chimneys are exposed to rain, snow, varying temperatures, combustion products and toxic exhaust gas. A thorough inspection of the chimney is required in order to determine if serious problems exist. A quality home inspection in NJ will provide a visual inspection of the exterior of the chimney. As always a level II chimney inspection is recommended at the time of the real estate purchase. A level II inspection is very thorough and will revel problems that are hidden from view during a visual inspection.

Home inspectors in NJ will perform a visual inspection of the accessible portions of the chimney interior. A level II inspection should be performed by a chimney specialist.

A rain cap is a metal cover that is installed at the top of the chimney that helps keep water out. Rain and moisture can damage the interior of the chimney. A second purpose of the hat is to reduce drafts going down the chimney in windy weather. When the rain cap/hat is missing water can infiltrate the chimney flue and cause damage to the interior of the masonry chimney or metal chimney. Water entering the chimney interior can cause enough rusting and corrosion in a metal flue that the chimney needs replacement. A rain cap should be installed the top of your masonry chimney.

A chimney cap is sometimes confused with a rain cap. A chimney cap is the mortar coat and seal around the top of a masonry chimney. The chimney cap seals that area in between the flue and the sides of the chimney. The purpose of the cap is to shed water away and to prevent moisture damage. A common problem with mortar caps is that the masonry does not slope away and project over the sides of the chimney.

Often the mortar caps are cracked broken or missing altogether. A cracked or broken cap should be repaired quickly in order to help reduce water damage. Regular maintenance is a key with the chimney top. Often the top of the chimney is neglected. What started out as a small repair can grow into a major rebuild and headache down the road.

Sometimes cracks exist through the masonry chimney. Sometimes the required air gap between the chimney liner and the chimney bricks has been omitted. If the gap is not in place then there will not be adequate room for expansion and contraction. As the chimney interior heats up the expanding liner may cause chimney cracking.

Water leaks can also be the cause of chimney cracking. There could be a missing cap or rain hat. Also open mortar joints can cause cracking of the chimney exterior. Open areas can allow water into the chimney structure where the freeze and thaw cycles can lead to cracks to the chimney itself or to its flue liner.

Chimney movement will often cause chimney cracking. A defective chimney footing may allow the chimney to separate from the structure of the home. The chimney may lean or bend causing chimney cracking.

The chimney flashing should be secured and water tight in order to avoid leakage inside the attic space. Proper flashing around a chimney consists of two different sets of flashings. The first set is called a step flashing. Sections of sheet metal are installed into the shingle courses and overlay the side of the chimney. Counter flashing is the second layer of metal and is let in the chimney mortar joints and folded downward to cover the top of the first set of flashings. Any small gaps should be completely sealed with a good quality flexible caulk. Often roofing cement is applied around the base of the chimney. Roofing cement or caulk is never an adequate substitute for a properly configured chimney flashing.
These are just some of the external areas of the chimney that we will be looking at during your quality NJ home inspection.

Chimneys can be a real problem area around the home. Chimneys should be inspected once every year. Certified home inspectors can look for loose or missing flashing and cracks in the masonry and other visible issues. If you take the time to inspect your chimney you will be able to save money down the road because small issues will not grow too much larger ones if addressed early on.

John Martino (64 Posts)

LookSmart Home Inspections, LLC is owned and operated by John Martino. He has successfully performed over 3000 inspections for clients throughout northern and central NJ and has an exemplary track record of customer satisfaction. Mr. Martino completed a 300-hour approved NJ Home Inspector training program and was mentored by one of the most respected names in NJ home inspections. He continues to attend over 30 hours of continuing education classes each year.


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Buying a house is one of life’s biggest decisions. Before you close, you’ll want a professional inspection of the house to ascertain its true condition. John Martino is a formally trained New Jersey home inspector and member of the American Society of Home Inspectors...ReadMore