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How To Clean Roof Stains

Start With The Gutters

Removing Algae Stains From Roof Shingles

You should begin your roof cleaning routine with gutters. This is especially true in situations where your gutters and downspouts look clogged. Use a leaf blower to clear out the leaves and clutter before washing the rooftop. You have to do this to clear the passageway for the water that flows away when youre cleaning the actual roof.

Without a clear gutter, your roof would become a soggy mess, or the gutters would overflow. That could then lead to gutter maintenance issues.

What’s Involved In Roof Cleaning

During roof cleaning, the focus is on killing and removing the algae or moss growth. Chlorine bleach, the same kind you use to whiten laundry or scrub your toilet, is enough to kill off moss and algae spores. The ARMA recommends a 1:1 ratio of bleach to water to clean a roof. They also advise against using a pressure washer on asphalt shingles, as the force of the water can damage them.

After being allowed to sit on the roof surface for up to 20 minutes, the bleach solution should be rinsed away with clean water. A few rain showers should be enough to wash any remaining algae off the roof. The person cleaning your roof might also use a leaf blower to remove any leftover pieces of moss.

What Are The Dark Streaks On My Roof

You may have noticed dark streaks across your roof. Given that moss grows upright on surfaces, and algae stays low and flush to the surfaces it grows on, its likely any dark streaks you see are algae.

Algae staining on roofs all start out being spread by wind, birds, and varmints, affecting homes across much of the United States.

This algae normally begins its lifecycle as airborne spores that will settle on your roof, especially those roofs that have asphalt shingles. The northern exposure of roofs has the most chance for algae to survive/thrive because that part of the roof is exposed to the least UV and dries last after morning dew and rain.

As the algae grows and spreads, it begins to look like large black streaks on your shingles.

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How To Clean A Metal Roof

How to clean a metal roof like a PRO!

By Roof Cleaning Pro – Pierce Parker of

Cleaning a metal roof can be a very tedious and lengthy process depending on which way you decide to go about it. There are many types of metal roofing types, coatings to work with, and variables involved on every job. Every metal roof cleaning evolution is different with no two being the same ever!

Best Metal Roof Cleaning Products

How to Clean Roof Stains

Plain Water

Dirt, dust, and other low-grade elements might wash off a roof with something as simple as water from a hose. Feel free to use as much water as necessary until the surface is clean.


This is the cleaning solution that most people need to use when cleaning their metal roof because its non-invasive and easy to do. This category includes mild laundry detergents, car washing soap, mild dish soap, and cold or hot commercial/industrial detergents.

  • Mix: 1/4 cup detergent per gallon of water.
  • Apply solution to surface using a sponge or a washcloth.
  • Let stand for 5 to 10 minutes.
  • Thoroughly rinse surface with plain water.
  • Solvents & Petroleum Solvents

    Solvents can be used to remove the tougher non-water elements that could come in contact with your PVDF-coated roof, such as oil, paint, grease, tar, and even some graffiti, according to Sherwin-Williams . Solvents should be used to clean only affected spots on the roof and should not be used to clean the entirety of the roof. Always check the recommended directions for cleaning on the products label and use accordingly.

    This class of cleaners includes:

    • Rubbing alcohol

    With this group, always keep in mind that you should wear protective clothing, use eye protection, and keep the area properly ventilated because most of these cleaners are toxic. Additionally, keep these solvents away from sparks or open flames, as they are flammable.

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    Can You Power Wash Asphalt Shingles

    No. You should never power wash a roof. A garden hose sprayer is the highest pressure a roof shingle should experience no higher than 70 psi. Since pressure washers commonly spray up to and beyond 3000 psi, they should be avoided. Shingle manufacturers even ask that shingles not be walked on, much less pressure washed.

    Using a pressure washer to clean your asphalt shingles can void their warranty and speed up the decay of your shingles. After pressure washing, youll likely notice tons of roof granules in your gutters because youve blasted your shingles too much. Avoid.

    Do You Have Stains On Your Roof If So Here Is How To Get Rid Of Them

    The common cause for roof staining is from organisms like moss, lichens, and algae. These organisms are known to feed off the organic roof material in shingles. The longer it is left untreated, the worse the damage to roofs. This is why removing stains should be a priority for homeowners. Roof stain is essentially fungus and mildew spores that are embedded in the shingles from nearby shrubbery, trees, and plants. All roofing is vulnerable to stain damage and that is why it is important to know how to remove roof stains and maintain them.

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    Technical Reviewers & References

    Pressure Washer Dos And Donts

    How to Remove Roof Stains

    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 roofs 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 dont recommend a power washer as a first resort for roof cleaning.

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    Question: What Is This Green Stain On My Roof What Causes It What Can I Do About It

    I have a two year old GAF room that has some stains that have developed under one side of the dormer and one side of the chimney.

    Trying to find out exactly what the stain is? – Anonymous by private email 2019/05/15


    That looks like green algae on the roof shingles and also on the lower portion of dormer siding boards.

    Is this the more shady side of the dormer?

    I also see what looks like oxidized paint or stain wash-down or perhaps even some spillage from when stain was applied – that light beige color on shingles below the dormer front corner.

    Reader follow-up:

    I would say yes, it is on the north side of both. The roof is only two years old, and no trees or anything hanging over. But what is weird is nothing is on the other dormer or anywhere else. Thanks for your help.


    That’s algae for you. You probably noticed you’ve also got some on the siding. Just which areas of the roof and dormer are most-shaded are probably the determining factors on this home, since the spores and other conditions that make algae available to land on and grow on building surfaces are pretty much all over.

    Reader follow-up:

    OK thanks for the information. I was going to purchase some Spray & Forget to try and have it removed, is this something you recommend? Thanks again for your help.


    A spray cleaner can kill off algae but

    Watch out: any bleaching agent may run down shingles or siding leaving ugly bleach stains so if you use a spray cleaner be sure to rinse the areas thoroughly.

    When Is The Best Time To Clean My Roof

    Another tip for washing your roof free of algae is to double-check the day you plan to execute. Verify the weather prediction and pick a moderate or overcast day with minimal wind. The less wind, the better to not accidentally spray the cleaners onto the rest of your house or a neighbors yard. A cool and overcast day is best for the algae to soak up the cleansers best and properly cleaned off for the roof.

    Be sure that any loose shingles or broken gutters have been cleaned. We dont want anything to go wrong when it comes time to clean your roof. Although we recommend using a safe and non-corrosive cleaner, there will undoubtedly be run-off from the roof washing. Youll want to move any lawn furniture or cover anything that cannot be moved and might get in the way of the run-off. Since mold and algae will be coming off the roof, youll want to be sure it doesnt land on any patio furniture or an outdoor kitchen area. The run off will also make your lawn wet and damp and it may take some time for it to dry out.

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    Should You Clean A Shingle Roof

    If your asphalt shingles dont look damaged, and the roof looks about the same as when it was installed, then it doesnt need to be cleaned. A little fading should be expected but does not necessarily indicate a need for cleaning.

    If you do notice damage, such as black streaks or white lichen splotches, then it is time to consider a clean. If you dont clean the shingles, the problem will not solve itself. Leaving dirt, lichen and other roof damage left to sit will result in several issues if not dealt with, such as:

    • Increased likelihood of blowing away
    • Aesthetically ugly and decreases home value

    Put Your Solution On The Garden Sprayer

    How to Clean Roof Stains

    If youre looking for the best results, start by mixing your chemical solution with a gallon of water, and a quart of chlorine bleach.

    Mix them well and place them in your container. You can even use a pump-style garden hose sprayer to get the job done fast.

    Youre given a lot of leeway in terms of where you want to pour your cleaning agent.

    As long as its a low-pressure sprayer, its all good. But, never pour your solution and use a pressure washer! Youll damage your asphalt shingle in the end!

    Also Check: How Long Should An Asphalt Shingle Roof Last

    Extends The Life Of A Metal Roof

    Like any household or outdoor item, regular cleaning will extend its life. For a metal roof, periodic cleaning helps maintain the integrity of the panels and helps remove any particles on the surface that could degrade the paint system or even the substrate. Luckily, paint systems such as PVDF are durable and engineered to last, but will still benefit from periodic cleaning to keep up the strength of the resin and coating.

    Why Is Roof Cleaning Important

    As the roofing system is a considerable investment, roof cleaning should be a priority in your home maintenance and your roof maintenance list. Some significant benefits of roof cleaning and maintenance include:

    • Keeping your family safe and comfortable inside
    • Prolonging your roofing systems life
    • Giving your roof a fresh new look
    • Preventing pest infestations
    • Allowing bigger energy savings

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    Formula For Roof Cleaning Solution For Black Molds Algae Stains

    Powdered household detergent 3 quarts

    Notes to the table above

    Be sure to wear rubber gloves when cleaning with this solution. [Note that trisodium phosphate is no longer used as a cleaning agent because it is an environmental contaminant. However substitute products may be available.

    Watch out: Be careful not to add a cleaning agent to bleach that can cause production of toxic chlorine gas. Any cleaner that contains ammonia, added to bleach, will react to form toxic or fatal chlorine gas.

    SIDING, WOOD CLEANERS, STAINS, PAINTS – a separate article on how to remove stains on siding & how to choose the proper paint or stain coating – we include formulas for bleach solution used to clean wood siding or trim stains

    Tip #: Know What The Black Streaks Are

    How to Clean Your Roof with Jomax Roof Cleaner

    Black streaking atop roofs is usually made up of algae called Gloeocapsa magma. Over time, it will develop a dark and hardened outer coating, which allows for the black algae stains that you see on the roof. The algae will feed on the limestone in the shingles and if its not taken care of, it will get more and more noticeable.

    It will continue to trap moisture and cause granule loss on asphalt shingle roofs, making them age prematurely and will damage the shingles.

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    Why Should You Remove Algae From A Roof

    The algae on your roof are unsightly and cause stains. In addition, algae interfere with the performance of highly reflective or cool roofs.

    Moss causes the shingles to lift or curl which increases the chance of shingles blowing off. It also changes the water flow of the roof which may cause damage to any porches or roof decks you have.

    Removing Sooty Black Molds On Plastic Or Painted Surfaces

    The USDA publication we cited above includes suggestions for removing sooty black molds . Quoting:

    Sooty molds can be indirectly controlled by reducing populations of sucking insects that excrete honeydew. Outdoor furniture can be hosed down with water during periods of honeydew excretion, particularly during drought. The growth of sooty mold fungi is inhibited by preservatives used in treated wood in rustic outdoor furniture.

    Here is the recipe for a good cleaning solution for removing sooty molds from plastic or painted surfaces:

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    What Causes Black Streaks On Roof Shingles

    Diagnosing what treatment to use when roof cleaning is as simple as taking a walk through the property with a professional. A professional will be able to take a look into what is actually growing on your roof, and will know the correct application in order to treat the algae and the amount of time it will take to remove it.

    Lets talk about the two types of algae we come in contact with on a daily basis.

    Identify The Source Of Roof Stains

    Removing stains from Asphalt Shingle Roofing

    Unfortunately, roof stains are usually an indication that your roof needs to be repaired or replaced. If you have black streaks on the north or west side of your roof, it may look like mold. In reality, those black marks are from algae that is growing on the shingles. Most roof shingles are treated with algaecide that can last for 10+ years. If you have an older roof though, the algaecide may have worn away.

    If you have a dark area of shingles, that may be a weak area on your roofing. Moisture gets trapped below the shingles and cannot evaporate like it does on the rest of the roof. Assuming the rest of the roof is in good condition, you would only need a roof repair for this not a complete roof replacement.

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    Can I Use A Pressure Washer On A Metal Roof

    The absolute very LAST technique you want to use on your metal roof is the strictly high pressure washing method with a high pressure tip and damaging pressure washer. A metal roof is very strong against many earthly elements but highly pressurized water or high pressurize anything is not recommended! In fact, pressure will not even do anything for you as far as cleaning the roof is concerned. A metal roof is constructed seamlessly or with screws and those screws have a rubber gasket and the high-end screws have a metal cap over the gasket for extra protection. Pressure Washing can damage these screws and expose the weak areas of your roof causing roof leaks in your metal. High pressure can also damage the finish on the roof as all roofs are made of different qualities, metal compositions, and more variables. The optimal amount of pressure you want to use when washing a roof is around 100-300 PSI and preferably HIGH-FLOW & LOW-PRESSURE. We consider HIGH-FLOW approximately 8 gallons per minute of water flow or greater.

    Three Of Shingle Stain Or Debris Removal: Clean The Roof Using The Gentlest Possible Method

    Watch out: don’t try cleaning asphalt shingle roofs without checking with the manufacturer about their recommended methods. For example using power washers , and some chemicals may damage the shingles and reduce the roof life. Other chemicals such as bleach may also cause staining on other building areas and can be unsafe if not handled properly.

    Power washing or brushing to clean a roof? it is possible to remove moss or lichens from a roof surface by gentle cleaning using a soft brush or a garden hose. Power washing risks damaging shingles by blowing mineral granules off of the shingle surface .

    NRCA’s James R. Kirby notes that if a roof’s appearance is not acceptable and cleaning it is the preferred method of improvement, asphalt shingles should be washed with a mild solution of chlorine bleach or mild detergent, gently applied with a sponge or hand-held sprayer.

    The surface then must be rinsed thoroughly with water. Kirby continues to warn that cleaning off roof algae is only a temporary fix – it will reappear unless we take steps to prevent future algae growth.

    Watch out: As we discuss at POWER WASHING ROOFS we do not recommend power-washing asbestos-cement nor any other roofing. In addition to damaging the roof surface, power-washing an asbestos-cement roof can create an environmental hazard.


    Some deck cleaning sprays such as StainhandleR roof and deck cleaner are also sold for use as cleaning solutions for stained roofs .

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