Signature Exteriors

Cleaning Your Asphalt Shingle Roof

Cleaning your roof is an important step if you live in a climate like Charlotte, where algae growth is typical on asphalt shingle roofs. Often mistaken as mold, algae growth appears as dark spots or streaks on your roof.

It’s common to drive through neighborhoods in the Charlotte area and see different homes with moss or algae build-up on the roof. Algae spores travel by wind or animals from one roof to another. Fortunately, most algae growth does not result in any severe damage to the shingles on your roof. Unfortunately, moss and algae growth can have negative impacts on the overall curb appeal and aesthetics of your home. That said, we frequently receive calls from Charlotte homeowners that are looking to have their roof cleaned or advice on cleaning the roof themselves to get rid of these unsightly stains. 

As a roofing contractor in Charlotte with over 40 years of experience, we typically recommend homeowners contact us before cleaning their roof themselves. An inexperienced homeowner can accidentally cause shingle damage if they attempt to clean their roof without any prior knowledge. This guide will explain the common do’s and don’ts of cleaning your asphalt shingle roof.


What Is Roof Algae? 

Roof algae is caused by gloeocapsa magma, a blue-green algae found in climates that experience warm and humid summers. Algae on roof shingles is common on homes with overhanging branches, standing water, clogged gutters, and poor roof ventilation. A very common filler found in asphalt shingles is limestone. Limestone provides nutrients to the algae spores allowing the algae to survive, spread, and darken. Taking steps to perform proper roof maintenance on your roof can help prevent roof algae from forming.  **SP Enter Roof Maintenance** 


How Does Roof Algae Affect Your Roof?

Fortunately, most roof algae is primarily an aesthetic concern rather than a common cause of roof leaks or roof damage. That said, algae forms when it has prolonged exposure to moisture, leading to the potential of roof mold. For any damage or stain on your roof, you’ll want to have a roof inspection by a professional before attempting DIY roof cleaning remedies.  



When we receive calls for roof cleaning services in Charlotte, we often hear similar reports about unsightly stains and streaks showing on the roofing system and questions on how to fix them. You can identify roof algae by the ugly dark streaks, spots, or green mossy fuzz growing on the roof. Roof algae can significantly decrease curb appeal. 

Home value

Our second most common reason behind our requests for roof cleaning in Charlotte is home buyers or sellers looking to clean their roofs before putting their homes on the market. If a new roof can boost your home value, you can imagine a stained roof can hinder it. Stained roofing systems are an eyesore and commonly used against the seller during real estate negotiations. Although roof algae are not severely damaging to shingles, they can signify more significant problems like prolonged moisture exposure throughout the roofing system. 

Wood Rot

Algae grow when there is moisture in their immediate environment. If you have algae growth on your roof, there is a chance the moisture has sunk into the wood decking underneath your asphalt roof shingles. This moisture can soften and rot the wood under your shingles and around your home, permanently compromising the strength and integrity of your home. 


Roof mold is another risk of moisture being trapped in your roofing system. Standing water and humidity, paired with growing roof algae spores, can be a breeding ground for mold to grow on your shingles and around your home. As you know, mold can pose serious health risks to you and your family. 

How to Clean Algae Off Roof Shingles

Now that we’ve gone over roof algae and its potential impact on your home and family let’s talk about the best practices for cleaning a roof and how to do it effectively. These tips are specific to cleaning asphalt shingle roofs. If you do not follow these tips, you may damage your roof shingles during the cleaning process. As a reminder, we always recommend contacting your local roofing contractor before attempting roof cleaning by yourself. 


DO: Use a sprayer attached to a garden hose that is filled with equal parts laundry strength chlorine bleach, and water. Spray the roof’s surface with this mixture and allow the mixture to sit on the roof for 15 to 20 minutes, and then thoroughly rinse the roof with clean water. 

DON’T: Use a pressure washer! The force behind a pressure washer can cause damage to your shingles or even loosen them, causing a potential leak source on the roof.


DO: Wet all foliage around your home thoroughly with clean water. After doing this, you will want to cover all foliage with a plastic cover. Once you have completed the final rinse of your roof, remove the plastic and rinse the foliage again to ensure no bleach solution remains, as this could kill any vegetation.

DON’T: Ignore the landscape around your home. The roof cleaning spray will harm any living plants and potentially cause them to die prematurely.


DO: Have patience. Any algae will wash away with rain, and moss will eventually loosen enough that it can be blown away with a leaf blower.

DON’T: Assume that the bleach and water solution will immediately remove any growth from your roof. It will take some time. Do not reapply the cleaning solution to your asphalt roof shingles looking for immediate results.


DO: Perform the cleaning of your roof on a cloudy and calm day with no wind and no chance of rain.

DON’T: Perform the cleaning on a sunny day. The sun will cause the bleach solution to evaporate quicker, which will limit the effectiveness of the solution.


DO: Determine that the roof is safe to walk on prior to getting on the roof. If the slope is too steep for you to walk on easily, bring in a professional. If you clean the roof yourself, make sure to wear well-fitting, closed-toe shoes with slip-resistant rubber soles. Take all safety precautions when on the roof.

DON’T: Clean your roof without taking all proper safety precautions


DO: Ensure to trim all bushes and trees close to your home. Trim back any branches that have overhang your asphalt shingle roof to expose the roof to sunlight. Ensure to clear your roof of all debris with a leaf blower and routinely check your gutters to ensure that they are clear of debris and that water is flowing correctly to ensure that the roof stays as dry as possible. Check out this article to see our experts’ 5 tips to prevent roof damage by trees.

DON’T: Wait until your roof is at the point of no return with moss and algae all over before taking action. It is much easier and cost-effective to address these items as they appear rather than waiting until moss or algae has overtaken the entire roof.


When Should You Call A Professional?

A licensed roofing contractor will know the best roof cleaning method to handle your roof algae issue. Professional roofing contractors can inspect your roofing system, determine whether the algae has caused any underlying damages, and clean your roof in a way that will not cause damage to your shingles or compromise the lifespan of your roof. 

You should contact a roofing company as soon as you notice signs of algae growth on your roof. The longer you wait, the harder it can be to treat. You should also call a roofing professional if you see any other discoloration, watermarks, dark spots, peeling paint, or rotting wood around the rest of your home. These are all very common signs you have a roof leak that may require roof repairs.  


Do You Need A Roof Inspection? 

If you need a roofing company to help clean your roof, consider contacting a local roofer to perform a free inspection. If you’re in Charlotte, Signature Exteriors offers free inspections and estimates for roof repairs, and you can click below to schedule your free consultation. If you aren’t local to Charlotte, make sure you hire a contractor with experience in asphalt roof shingles and roof cleaning. Contact Signature Exteriors today for a free inspection!