Our Company Blog

Identifying Chimney Discoloration

Stains on the sides of your chimney structure can take away from the curb appeal of your entire home. And while chimney discoloration can make your chimney look unsightly, it may also indicate a deeper chimney problem. The following are four of the most common types of chimney discoloration, what causes them, and how it could be affecting your chimney system.


Black and brown stains

Black and dark brown areas of discoloration on the inside and outside of the chimney are typically caused by soot. Soot stains are very common on older chimneys as well as those that have not been properly maintained.

Interior soot stains, especially those on the masonry directly above the firebox, are usually purely cosmetic. This kind of discoloration is most often caused by a lack of regular chimney cleaning, repeated use of green or unseasoned firewood, or a fire that was too large or otherwise out of control.

When found on the top and sides of the chimney, soot stains are typically the result of an excess of creosote in the chimney. Although creosote is naturally produced in wood burning fires, it can be made worse by allowing fires to smolder, burning green wood, or having a flue that is improperly sized. Because creosote is extremely flammable, it is important to have your chimney swept regularly – especially if black or dark brown discoloration appears.

Gas fireplaces and heating appliances should never have soot staining on the chimney. If this kind of staining is spotted on the chimney of a gas fireplace, it is important to stop using the fireplace and call a chimney sweep. Soot staining on gas fireplaces often indicates a malfunction or leak; this could lead to a buildup of dangerous gasses like carbon monoxide in your home.

Green stains

While it may be difficult to distinguish a dark brown stain from a dark green one, they have very different causes. Dark green discoloration n a chimney can be caused by algae and mold growth. This typically occurs when too much water repeatedly comes in contact with one area of the chimney, such as when a sprinkler repeatedly hits the same spot.

Red rust stains

Rust stains are commonly seen on homes with prefabricated or metal chimneys and can come in a rainbow of reds, browns, and oranges. This kind of discoloration is a sign that the metal chimney chase cover has begun to rust. If this type of discoloration is discovered, a chimney sweep should evaluate the condition of the chase cover before it is replaced to see if there has been any water damage to the rest of the fireplace and chimney system.

White stains

Powdery white stains on a chimney structure are a phenomenon known as efflorescence. Efflorescence a buildup of the mineral salt that gets left behind as ground and rain water evaporates. Exterior efflorescence is usually benign and can be caused by a number of sources including rain and sprinklers. However, if efflorescence appears on interior masonry, it is almost always a sign of an interior chimney leak.

Chimney staining and discoloration can be a black mark on your home’s beautiful exterior – literally. To diagnose the cause of your chimney discoloration and keep it from coming back, call the experts at Pristine Sweeps today.

Draft Issues With Chimney Caps

Although not unheard of, it is rare to find a modern home with an uncapped chimney. In addition to protecting your fireplace system from moisture, animals, and debris, chimney caps can also help improve fireplace drafting.

The presence of a chimney cap does not eliminate draft issues, however. There are a number of draft issues that can occur even with a chimney cap. Below are some of the most common chimney cap draft issues.


Draft-increasing chimney cap

While all chimney caps are designed to improve drafting, homes in areas with extreme winds may still experience downdrafts even if they have a chimney cap. If you notice downdrafts or smoke blowing back into your home on especially windy days, you may have this problem. When this happens, a special draft-increasing chimney cap may be needed.

Draft increasing chimney caps work by creating stronger updrafts. Designed to force wind around the top rather than down it, these chimney caps increase the air velocity and decrease static pressure around the chimney structure. Doing this forces the smoke upwards and out of the chimney while preventing the wind from drafting back down no matter what direction the wind is blowing.

Clogged chimney cap

Chimney caps are designed with mesh sides that help keep animals and debris out of the chimney structure. However, these same wire sides can become clogged on both the outside and the inside. Clogged chimney caps can create serious draft problems – as well as fire hazards – if the buildup of debris is not removed.

Inside the chimney, chimney caps commonly become clogged by excessive creosote buildup. This is often seen in homes that have not had their chimneys swept or inspected in several years. Creosote buildup is especially dangerous as it is a flammable substance; when accidentally ignited by a spark or ember, creosote is the leading cause of chimney fire.

In addition to creosote, chimney caps can also be clogged by debris such as leaves, twigs, roofing materials, and even stray Frisbees. Likewise, animals attempting to access the chimney or nesting under the chimney cap can cause blockages. When any portion of the chimney cap mesh is covered, the chimney may not be able to draft properly.

Improperly installed chimney cap

Another common cause of draft issues with chimney caps comes from improper installation. If a chimney cap was not properly installed, it can shift or become easily damaged over time. This can affect airflow and drafting. Likewise, a chimney cap that does not fit properly or is not sized correctly can also cause draft issues. If the chimney cap is too big or too small, the fireplace will not be able to draw in the right amount of air to force smoke and other byproducts of combustion up and out of the chimney. Likewise, improperly installed or fitted chimney caps can cause structural damage to the rest of the chimney structure.

Even if your fireplace system has a chimney cap, you may still experiencing drafting issues. If your fireplace is not drafting correctly, contact Pristine Sweeps today!