Is Roof Cleaning Necessary? Everything You Didn't Know About Scrubbing Your Shingles

If you're ever outside looking up at your roof wondering if that black stuff growing on some of the shingles is mold, mildew, or soil that somehow made its way up there. You need to ask yourself, is it time for a complete roof replacement or will a good cleaning resolve the issue, then you should keep reading. 


More than likely, that unidentifiable sludge is algae growth. According to the Asphalt Roofing Manufacturers Association (ARMA), the spores reach the roof by a combination of wind and birds. Then the algae will begin to grow on roofs in areas where water or moisture both collect.

Do you have trees above your home? The shade from the trees and moisture create an ideal habitat for moss growth. Which results in those green fuzzy patches of moss to begin to grow your roof.

So, if you're seeing either moss or algae growth on your roof, what should you do? A roof cleaning, a complete replacement, or should you just leave it alone?


According to ARMA, while algae growth isn't totally harmful to asphalt shingles, moss is. Moss can make the edges of the shingles curl upward, making them more likely to blow off the roof during windy weather. This is a good reason why having your roof cleaned annually is a great way to extend the life of your shingles or any other roofing material your home may have.

Now, algae won't completely harm asphalt shingles, it does have the potential to negatively affect their performance, especially if your home has a reflective or cool roof. Black algae growth will interfere with the reflective properties of the roof and limit its cooling benefits.

A big drawback of giving your roof a good cleaning is that it's just a nuisance. No one is ever thrilled about the idea of climbing up on their roof and hosing it down with a chemical cleaner to kill off any algae or moss growth. Luckily for you, the National Roofing Contractors Association advises homeowners against most D.I.Y work when it comes to roofs, including cleaning them. Simply put, leave roof work to the pros.

A commonly overlooked issue with roof cleaning is the cleaning product it's self. Usually bleached based, it can harm any garden plantings or vegetation growing near or around your home. This is why you will see professional roofing contractors always water any nearby plants and cover them to protect them from chemicals before cleaning your roof.


During all roof cleanings, the main goal is to kill and remove all algae or moss growth using a roof cleaning solution. The main ingredient being chlorine bleach, the same kind you use to whiten laundry or scrub your toilet, which is enough to kill off all those moss and algae spores. The ARMA recommends a ratio of 1:1 (bleach:water) to clean a roof. They also advise homeowners against using machinery like a pressure washer on asphalt shingles, because the force of the water can uplift, damage, or completely remove them.

Once the roof cleaner sprayed on and let sit on the roof surface for around 20-30 minutes, the cleaning solution should be rinsed away with clean water. With a few rain showers being enough completely wash away any remaining algae off the roof. An extra step that most roofing professionals will take after the roof has been cleaned is the use of a leaf blower to remove any leftover pieces of moss.


This is the question all homeowners will ask themselves more than once during the lifetime of their home. So, if you're outside looking at your roof and thinking it looks a little worse for wear, maybe it's time for a good cleaning. The buildup of algae and moss on a roof can make the shingles look like they are in worse condition than they truly are. So, if you're unsure about the condition of your roof, hiring a professional roofing contractor to come out and inspect it is a great option, they'll be able to update you about its condition and which steps you should take to remedy any issues or concerns. From a simple cleaning all the way to complete replacement.

After the inspection is complete and it turns out that your roof needs replacement, your contractor might recommend asphalt shingles that contain copper or another material that helps to repel algae growth. A true roofing professional will always give you tips on keeping your roof clean and how frequently you should schedule cleanings.


You now have the information you need to make sure you have a clean, healthy, and whole roof.  So, remember for a simple problem like algae stains or moss growth, hiring a professional cleaning service is often all it takes to get your roof back to looking pristine and avoid any costly problems down the road. A routine soft-washing increases the lifespan of your roof and can delay a more expensive replacement. You can also explore options like installing algae-resistant copper strips at the top of your roof to protect shingles moving forward. Or when it’s time to replace your roof, homeowners now have options from shingle manufactures that have new algae-resistant shingles to choose from.

The first step is getting our professional team up on your roof for an estimate and a maintenance plan. A safe, effective spring cleaning is often a terrific first step.

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