Chimneys are great when they do their job efficiently, but can be a big safety hazard if not functioning properly. Not all homes have chimneys, but in homes with chimneys present, there can be variances in regard to the types of chimneys used for the exhaust of combustive appliances or fireplaces.
Types of Chimneys Include:
Lined or Unlined
Pre-Fabricated Inserts
Pre-cast Concrete
Masonry
Chimneys can be lined or unlined, and in most cases should always be lined, regardless of what they are exhausting. There are pre-fabricated inserts used for wood, natural gas, LP gas, or a combination of wood and gas. These are typically metal pipes inside wood-framed chases, but not always, and like anything else in a home, this can vary from home to home, and a good example of variance would be a pre-fab with a direct vent instead of a wood framed chase.
There are pre-cast concrete chimneys built in factories and then trucked to a building site and erected. Also, there are masonry chimneys that are built on site with individual bricks and mortar. In this respect, pre-cast chimneys are unique. However, like masonry chimneys, they are vulnerable to seismic activity or home settlement, but unlike masonry chimneys they are also subject to cracks that are induced by the interaction of moisture and a chemical additive called calcium chloride that causes the reinforcing steel within the chimney to expand and crack the chimney wall. Such cracks can be small, but they are nonetheless subject to stringent repair methods that are stipulated by the manufacturer. However, if any crack penetrates the chimney wall it cannot be repaired and the chimney must be removed. For this reason, it is recommended that all pre-cast chimneys be video-scanned or certified by a specialist prior to closing.
With masonry chimneys built on-site, and/or pre-fabricated inserts, it is recommended by Area Wide Home Inspection that these also be further evaluated by a qualified chimney or fireplace specialist, since a full interior inspection of these systems require specialized tools and equipment that are beyond the scope of a home inspection.
Further evaluation of any type of chimney, by a chimney or fireplace specialist will not only be helpful in determining whether there is a liner present, but also many other potential hidden defects. And, if the chimney is in good shape, the money spent on this type of specialized inspection is good for peace of mind - and at the end of the day, isn't that just what we all need?