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3 Ways to Clean Black Roof Stains

August 4, 2022 | 3 min. read

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Being a homeowner isn’t as simple as purchasing a home or making cosmetic decisions. Many parts of your home come with regularly scheduled maintenance that, if not completed, can leave your home in disarray. 

When your roof was new, it was beautiful and added curb appeal to your home. Over time, you may have noticed black streaks and algae growth. 

Can you clean the stains off of your roof? The answer is yes; you can clean your roof. But there are methods to wash your roof that need to be followed to maintain its longevity.  

Rescue My Roof has served homeowners in Southeastern Wisconsin for over a decade. Our expertise in all things roofing has led to high-quality roofs across the state, so we know a thing or two about how to clean your roof safely. 

This article will briefly summarize the recommended methods for cleaning your roof. The next time you notice those pesky stains ruining your roof, you’ll know how to tackle them. 

What Are Those Stains on Your Roof?

Black stains on an asphalt roof.

While rusty flashings or vents can cause roof stains, they are most often caused by algae growth.

The real villain: Gloeocapsa Magma – or blue-green algae. 

Algae growth begins as small spots, then grows to visible streaks. By the time homeowners notice it, it has typically been on the roof for over two months. 

All roofing types, including metal, can have algae growth, but asphalt shingles are at the highest risk. 

How Do You Get Rid of Stains on Your Roof?

You can do two tactics to tackle algae growth: cleaning the roof yourself or investing in an algaecide to kill algae growth.

However, here are some tips to follow if you choose to clean your roof yourself. 

Here are some things you need to know:

1. Pressure Washer Do’s and Don’ts

Professional power washing a cedar shake roof.

If you choose to clean your roof, you should not use a high-pressure washer.

Asphalt shingles have a top coating made of granules. Granules are your roof’s first line of defense against moisture.

When you use high pressure to wash your roof, you may wash some of those essential granules away or even cause some shingles to lift. 

If you need to use a pressure washer, it is best to use it on its lowest setting. Even then, we don’t recommend a power washer as a first resort for roof cleaning. 

2. Clean Your Roof With A Bleach/Water Solution

Professional cleaning algae off an asphalt roof with a cleaning solution.

If you want a clean roof on a budget, there is still a way to clean your roof without using a power washer. 

Here’s how you can achieve a clean roof and happy home: 

  • Cover all vegetation and landscaping
  • Wear eye protection, rubber gloves, and wear slip-resistant shoes
  • Check your shingle manufacturer’s website for specific cleaning recommendations

If you are looking for a roof cleaning solution to get rid of algae, here’s what Bob Villa recommends

  • 1 cup of trisodium phosphate (you can find it at your local hardware store)
  • 1 gallon of bleach
  • 5 gallons of water

Spray your roof down with this solution from top to bottom, allow it to soak in for 15-20 minutes, then rinse. 

Go slowly and use even strokes to achieve the cleanest roof possible. 

3. Hiring a Professional to Clean Your Roof

If you don’t want to climb on your roof to clean it – we don’t blame you. Many homeowners are in the same boat. But there’s always another option: hiring a professional for a roof cleaning service. 

Roofing contractors use algaecides to ensure that those pesky black stains are gone and are unlikely to come back. 

The result is a beautifully restored roof and little work for you!

How to Prevent Black Roof Stains

We’ve covered all the ways to clean your roof, from DIY bleach solutions to hiring a professional, but is there a way to prevent algae growth? 

Trimming excess tree branches, cleaning off roof debris, and keeping your gutters clean can help keep algae growth at bay. Any standing water or debris can be a breeding ground for algae we want to avoid. 

Additionally, you can install a copper or zinc strip along the peak of your roof. 

The metals contain algae-killing molecules. When water washes down your roof, the molecules can kill any algae lurking around. 

You can learn more about roofs and algae growth with “Roof Staining, Algae Growth, and More” and “The Top 5 Problems With Asphalt Roofs.

Are you experiencing problems with algae growth and staining on your roof? Rescue My Roof has over a decade of experience treating algae and roof stains. You can contact us today to get an estimate for our roof cleaning services.