What Causes Dark Stains on Roofing?

Should You Clean Your Roof?

If you spot stains on your roof, your first thought might be to climb up on a ladder to clean them. Before you do, remember that working on a rooftop is one of the most dangerous things you can do. Falls from roofs are the main cause of construction-related injuries.

The safest approach is to call a professional roofing contractor who has the right experience and the right equipment to do the cleaning safely.

If you decide to do it yourself, follow these guidelines:

  • Start by sweeping away leaves and debris.

  • Use your broom to scrub tough stains.

  • Finish by rinsing with a regular hose. Never use a power washer on your roof.

Those Dark Stains Are Probably Algae

If you see dark, nearly black stains and you have an asphalt shingle roof, it's likely that you have algae growing on your roof.

Gloecapsa magma is the name of the type of algae that usually grows on roofs. It's attracted to them because it feeds on the calcium carbonate in asphalt shingles.

Its spores travel by air. If one house in your neighborhood has algae growing on the roof, it's easy for the algae to spread up and down the block.

How to Remove Algae from Your Roof

It's not difficult to remove algae from your roof, but be sure you use the correct cleaning methods.

  • Don't use a power washer. Power washers can damage asphalt.

  • Don't use a bleach solution, because it will damage the vegetation around your house and weaken the shingles.

  • Use a diluted mix of trisodium phosphate and water.

  • Rinse it off with a regular hose.

Prevent Algae from Forming on Your Shingles

  • Check your roof regularly for the telltale dark stains, and clean them immediately.

  • Trim branches that are blocking the sun from your roof.

  • Ask your roofing contractor about installing zinc or copper strips along your asphalt roof.

Red Stains Might Be Rust

If you see red or reddish-brown stains on your roof, they could be from metal flashings, chimney linings, antenna and satellite mounts, metal fasteners and other metal roof components.

Rust won't damage your roof shingles, but it can damage the metal components on your roof. If your flashings are rusted, dangerous roof leaks might be in your near future.

You should examine the rust spots to ensure that they're not caused by leaks. If the flashings and chimney lining are secure, you don't need to worry about rust except as a cosmetic issue.

Can You Clean Rust Stains from Your Roof?

You can, and you might be surprised to learn that all it takes is a simple household ingredient.

To clean the rust, use undiluted household vinegar. Spray it directly onto the rust stains. If the stains are stubborn, you can use your broom to scrub them.

Debris Can Also Cause Staining

Letting leaves, twigs, seeds, grass, and other organic materials pile up on your roof can cause stains. That trapped material isn't just unsightly. It can also be dangerous because it holds moisture that can lead to mold growth and other long-term problems.

If your roof is covered in debris, it will be even more dangerous to walk on. All that loose matter makes the roof surface uneven and slippery. It's probably a good idea to leave this one to the roofing professionals.

Professional Roof Care Can Keep the Stains Away

If stains on your roof bother you, get rid of them quickly and easily with a professional roof cleaning. A roofing contractor can inspect your roof while cleaning it and alert you to any problems with the flashing, shingles or gutters.

Keep your roof clean and leakproof with regular maintenance. Get started by calling Last Call Exteriors today.