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White, Black, Red, Green, and Brown: Identifying Staining on Chimneys

During the warm weather, many homeowners are enjoying the sunshine. It’s the perfect time to take a dip in the pool, run through the sprinklers, and even get some of that yard work done. As you walk around the exterior of your house, you may notice different color stains are covering portions of the chimney. Stains that appear on the chimney can be unsightly, but it can also be a clue of a potentially severe issue when you know how to decode the stain’s color.

Black Chimney Stains and Masonry Damage McMinnville, TN Black Stains

The black stains on the chimney are typically indicative of soot. The powdery material is often spotted on the external masonry surfaces around the chimney cap, but windy conditions can cause soot stains to appear practically anywhere on the chimney. However, not all black stains are soot. Tarry, crusty black stains are creosote, a highly flammable substance.

Brown Stains

The brown stains that are appearing on the chimney are almost always creosote. Creosote is a natural by-product of combustion. As the contaminant is expelled from the flue, it may stick to the chimney cap and sides of the chimney. When black or brown stains appear on the chimney or fireplace, it usually means that the chimney is either not appropriately cleaned or as often as it should. Also, if there are creosote stains on the external masonry surface, the chances are high that there is a creosote buildup in the flue. Since creosote is flammable, contact a chimney sweep to remove it as soon as possible.

Green Stains

You may notice dark green stains that resemble plant growth, particularly around the foundation, chimney cap, chimney crown, and roofline. It’s usually algae, and these microorganisms grow in standing water. Humid environments are also conducive to algae growth.

Red Stains

Red or reddish-brown stains are most prevalent with a prefabricated chimney due to rust on the metal chimney chase cover. It usually occurs when there is a water leak around the chase cover, and the rust stains will drop down the sides of the chimney. Since water is likely leaking inside the chimney, it needs the immediate attention of a qualified chimney technician to prevent further damage. The chimney technician will inspect the chimney and fireplace and replace the damaged chimney chase cover.

However, masonry chimneys can also develop rust. If there is hard water or elevated levels of iron, calcium, and magnesium deposits in your municipal water supply, you may notice reddish-orange rust stains appearing around the bottom of your exterior walls and chimney after watering your lawn.

White Chimney Stains, Madison, TN

White Stains

White stains or patches forming around the chimney exterior are knowns as efflorescence. It occurs when moisture seeps into the bricks, causing the salts in the cement to rise to the surface. While efflorescence can happen in any climate, it is more prevalent in colder climates that experience frequent freeze-thaw-cycles. Since efflorescence is a type of water damage, a chimney inspection is necessary to determine if there is a leak in the chimney.


How to Prevent Chimney Stains

While it may be tempting to skip it because everything appears to be in working order, annual chimney inspections and cleanings are the best way to prevent chimney stains. Chimney stains are more than a visual nuisance. They are often a sign of a potentially serious issue like a water leak or excessive creosote residue. A Certified Chimney Sweep® will determine the cause of the stains and recommend solutions for removing them and making any necessary chimney repairs to prevent its reoccurrence.