Common Problems with Older Chimneys

With the Houston real estate market booming these days, I am getting a lot of phone calls from home buyers that are purchasing older homes that have a chimney that they would like to use. There are a few differences with chimneys built in older homes than with those built in newer homes. The newer chimneys have been built with new materials and conform to modern building codes. In order for your chimney to function safely, you might have to make some modifications.

Houses that were built more than 60 years ago usually have masonry fireplaces and chimneys. Metal, factory built systems only began to appear in homes in the 1950s. The biggest problem that we see with older masonry chimneys is that they don’t have a chimney liner. A chimney with a chimney liner is safer and more operates more efficiently than an unlined chimney.

There are many structural issues that are associated with unlined chimneys. They usually don’t have the proper draft or air circulation causing the appliances that are connected to them to perform inefficiently. Unlined chimneys over time may leak noxious gases into the home because of chimney cracks. Interior condensation is another problem is that masonry chimneys that have gas appliances connected to them has a tendency to accumulate excess condensation causing eventual deterioration. Condensation mixed with tar from burning wood forms a residue called creosote that must be removed or risk causing a fire is another issue.

You also have to consider the local laws if you decide to change to the construction of a structure as the system must come up to existing building code standards. If you decide to add a new furnace or boiler, a woodstove or insert, the chimney must be lined at that time. Insurance is another important matter. In some cases if you make changes without improving the chimney you can find yourself without insurance. It’s important to check with your insurance company before making any significant changes to the structure. For all of these reasons we recommend that a chimney liner be installed in all chimneys before they are used for any application.

Because masonry chimneys are constructed with bricks and mortar they have specific issues related to the age of the bricks. Chimneys that were built before the 20th century were made of different materials and are in most cases stronger than masonry chimneys that were built in the last century. However, they are both at risk for damage caused by the shifting ground underneath which causes the brick to break and crack. The sun, wind, rain and snow also have an impact on the bricks and mortar which bonds the bricks together. When the mortar is too old and wears out you can either rebuild or re-point your chimney. Re-pointing addresses the mortar issue without having to replace all of the mortar by removing an inch if the existing mortar and replacing it with new mortar.

In order to reduce the risk of water damage to the exterior of the chimney is by waterproofing it. While the bricks soak up the rain and usually dry off quickly, brick that isn’t exposed to the sun tends to retain the water. During the colder months, that water expands inside the bricks creating holes and cracks. By waterproofing your chimney will ensure that water doesn’t enter.

Many older homes are located in areas surrounded by trees and leaves that enter from time to time. If an older home is located in the country near wildlife, animals such as raccoons and birds also enter the chimney to have a warm place for the winter.   In order to keep them out a chimney chase cover or chimney cap can be installed on top of the chimney.