Inspections
Our company does a lot of chimney inspections, often as part of a real estate transaction. The exterior is checked for areas of deterioration that will allow water to enter the chimney and cause further damages. If the chimney exterior is not maintained, the repairs will eventually become quite costly.
A level 1 inspection is a visual inspection of accessible areas.
"Top to Bottom" Inspection...
First, a ladder is put up to check for cracking above the roof. (Generally the top of the chimney has the most deterioration.) Next, the interior of the chimney including the flue liner and smoke chamber is checked with a high powered spotlight. Any questionable areas in the flue can be checked with a video scanning system. This consists of a remote video camera mounted on rods and extended into the chimney. Sometimes the flue needs to be cleaned prior to inspecting.
A level 2 inspection adds video scanning of the interior.
Unfortunately some key areas of chimney safety cannot be checked with the level of inspection that is the industry standard. A "level three" inspection involves opening walls to check for any hidden combustibles next to the chimney system. This is generally considered to be impractical. It is possible, however, to drill holes from inside the fireplace into areas of concern, insert a bore scope and view the hidden areas. The holes are then cemented up. NOTE: Request for this type of inspection must be made prior to our arrival to ensure that the equipment is available.
A level 3 inspection, when required, involves opening walls to check for combustibles.
The main area of concern is between the mantle and smoke chamber where there generally is a combustible header supporting the framing above. The second area of concern is the back wall of the firebox on a chimney that is not built on an exterior wall.
Just because a chimney has been used for many years does not mean that it is safe. Wood next to a fireplace will ignite at 500° F when it is new. After years heating it will pyrolyze (char) and eventually ignite at 200° F. This can happen even when there are no cracks in the masonry. Since it takes time for heat to travel through masonry, it is best to have shorter fires and not pile on the wood too high.
It is possible to use insulating refractory materials in areas of concern to protect known or suspected combustibles from heat.