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How to Identify the Cause of Chimney Staining

chimney stains from leaky chimneyIt’s spring cleaning season and getting a chimney cleaning should be on your list if your home has a fireplace. Tackling chimney stains is one home improvement project that you shouldn’t DIY. If you notice stains on your chimney, it is a sign that you need to call in a chimney sweep for a professional cleaning and inspection. Discoloration on a chimney doesn’t happen because of old age or use. It’s a warning that there is an underlying problem.

The color of the staining on your chimney can give you a clue to what the problem is. There are four common types of staining:


1. Black Stains

Black stains are usually located around the top of the chimney. As you may have guessed, this discoloration is caused by soot and creosote. It happens when these combustion byproducts build up on the chimney cap and then get partially washed away by rain water. A well-functioning chimney will not produce enough soot and creosote to build up on the chimney cap. If this is happening, it means that your chimney is not operative efficiently. Large deposits of creosote in the chimney may be cause it to perform poorly. In that case, a professional cleaning will solve the problem. A certified chimney sweep will be able to see if there is another root cause during the cleaning.

2. White Stains (Efflorescence)

White, powdery staining is called efflorescence. This staining occurs when water evaporates out of masonry and leaves behind salt deposits. The staining itself is easy to remove but it is a sign of a much bigger problem. Water deteriorates bricks and mortar. If your chimney is absorbing enough water to have efflorescence, it may have a broken chimney crown, or leaking chimney cap that are allowing water in. Efflorescence will be the least of your problems if water continues to get into the chimney. Along with weakening the structure of your chimney, water damage can spread to your home ruining walls, ceilings and floors. Hiring a certified chimney professional to inspect your chimney is the best way to identify how water is getting into the chimney and solve it before the problem escalates.

3. Dark Brown or Green Stains

Dark brown and green stains are typically a sign that mold is growing in the chimney. Like efflorescence, mold is caused by excess moisture. It could be growing on the chimney because of an exterior problem, like a clogged gutter overflowing to the chimney. It may also be growing in the chimney because of a chimney leak. Mold growing on the outside of the chimney is not likely to be toxic, but it may still cause allergic reactions. Mold growing inside of the may be toxic mold because of the chemicals in the chimney. If you notice brown or green stains, it is a smart idea to call on a certified chimney sweep to clean and inspect your chimney to remove the mold or algae and identify the source of the problem.

rusty read stains on chimney in need of inspection4. Rusty Red Stains

Rusty red stains on the chimney are a sign that a metal chimney component, like a chimney cap or chase cover, is rusting. If your chimney cap or chase cover is rusting, it will flake and begin to develop holes that will allow water, insects and other pests to get into your chimney. This can lead to other problems like water damage or a blocked chimney from a dead pest. Proactively maintaining your chimney by replacing rusting components can save you money in the long run.

Don’t hesitate if you notice stains on your chimney, give us a call at Northeastern Chimney! Our team of CSIA-certified chimney sweeps will clean your chimney and inspect it to identify the source of the stain. Set up an appointment today!

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