You may think a weathered look gives your chimney character, but stains can be a sign of an underlying problem. Let’s look at the various stains you might see on your chimney and what causes them.
If you live in a humid environment, you’ll probably notice green stains dotting your chimney, which are usually algae. Algae is unsightly but isn’t considered a hazard. It could also be mold, which may indicate a water leaking issue with your chimney. You would want to get a water problem inspected and repaired right away!
Black chimney stains are one of the most common and are caused by soot. Soot stains mainly appear on the crown, but wind can spread them everywhere.
Brown stains are typically caused by creosote, a natural byproduct of burning wood. If you see these stains on your chimney, it could mean it needs to be swept. Creosote is corrosive and highly flammable, so it’s crucial to hire a professional chimney sweep to take care of it as soon as possible.
Red stains typically mean rust and often affect factory-built chimneys. Rust happens whenever water leaks from your chase cover and drips down the sides. If you see red stains, call a chimney professional as soon as possible because water leaks can cause damage to the chase cover if they’re not repaired and lead to mold growth in your home.
White stains come from a process called efflorescence. Efflorescence is when moisture seeps into the bricks, causing the salt in the mortar to go to the surface. Efflorescence typically happens in cold climates, where chimneys undergo a freeze/thaw cycle. Because efflorescence results from water, it could signify that you have moisture damage, which, if left unchecked, can cause brick spalling, loose mortar joints, and a compromised chimney structure.
Preventing Chimney Stains
The most effective way to prevent chimney stains and the damage that results is to schedule an annual inspection by a trained professional. As mentioned, some stains are nothing more than an eyesore, but others could result from an underlying issue that can lead to damage or fire. Certified chimney experts can quickly determine a stain’s cause and determine if your chimney is at risk.
Besides scheduling a chimney inspection, it’s wise to invest in a waterproofing product since many stains are caused by moisture. Waterproofing prevents many moisture-related stains and extends the lifespan of your chimney.