Remove Roof Moss, Roof Mold & Roof Algae

Unlike roof moss which is easily identified, those ugly black streaks and stains on your shingles though appear to be some sort of roof mold, a more accurate description would be to call it roof algae.  This is a hardy species of algae called Gloeocapsa Magma, and if you aren’t using the right chemicals or methods it can be extremely difficult to remove.  Call it roof mold, roof algae, roof mildew, or whatever else you want, but just be sure to clean it off in a timely and safe manner.

Just to be thorough, there are other types of organic growth that can form on a roof other than roof algae (or mold).  There’s also the possibility of lichen or moss growth.  Lichen is usually a whitish color, but it can also have tones of green, yellow, and brown.  It often forms in patches of individual circles, each averaging about the size of a dime.  It’s also noticeably raised from the surface, unlike the black algae stains.

Roof MoldRoof moss, on the other hand, almost always has a green color and if left untreated for several years will become so thick as to be noticeable from the ground.  I’ve seen some situations where it’s been ignored for so long that it literally looks like a roof is covered with green carpet.  Honestly I don’t know what people are thinking when they allow this to happen to their home especially when you can remove roof moss fairly easily most of the time.

So how does one go about treating a roof with lichen and/or moss?  Well, in most cases it should be handled in the same manner as the black algae roof stains (or “roof mold“), which has already been described in length on this site.  In a nutshell, a bleach or chlorine-based solution applied with non-pressure methods will kill lichen and moderate moss growth almost instantly.  It should turn a whitish color within minutes, which tells you that it’s dead.  Unlike black algae stains which come off immediately with the rinse phase of the cleaning, dead lichen and moss will require a few heavy rains to finish rinsing off the roof.  It could take awhile but rest assured that lichen and most moss situations, once dead, will eventually dislodge and rinse off the roof thanks to mother nature.

If you are the impatient type and want the lichen and moss removed immediately, you’ll have to use a pressure washer, but as you should know by now I highly discourage the use of high pressure on a roof.  In those rare cases where the moss is extremely thick and out of control (this is more common in the northwest) your only choice might be to use a pressure washer, but even in these extreme scenarios you should dial down the pressure and use extreme caution.

In summation, black roof “mold” stains (algae) should come off immediately if using the proper methods.  Roof mold removal doesn’t have to be rocket science, people. White or green lichen and roof moss removal on the other hand, can be achieved by the same chemical solution but will need a few heavy rains to finish rinsing away.  If this all just sounds like too much of a hassle and you’d rather keep your feet safely on the ground (good idea) then do take a look at our directory of non-pressure roof cleaning services.  There’s more than likely a company in your area that knows how to remove your roof algae in a professional and safe manner.

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Roof Stains Should Be Cleaned Without Scrubbing

In my dealings with potential customers who want their black roof stains removed, I’ll sometimes run into someone who thinks the roof should be scrubbed clean with a hard-bristle brush in conjunction with some sort of cleaner.  At first this “method” might seem to make sense, but it’s a definite no-no and I’ll tell you why.

I can pretty much guarantee that if you try to clean your roof stains with aggressive scrubbing or agitation, you’re going to lose a lot of shingle granules in the process.  With enough force these will pop right off of asphalt shingles, which is why I also do not recommend roof cleaning with a power washer.  Granules do more than just add the color to your shingles.  They are vital to your roof’s health because they reflect sunlight, thus keeping your attic cooler and your AC bills lower.  If you think your attic is warm now just climb up into one that is covered by a roof that is missing a lot of granules or is covered in black algae stains – you’ll probably notice the difference in temperature.  In general, the quicker your roof loses granules the quicker it will lose its integrity, and the quicker you’ll need to get a new roof.  So hopefully you can see how important this so-called “shingle grit” actually is.

Roof StainsThe other reason you shouldn’t be scrubbing or pressure washing your roof stains is that in most cases it’s simply not necessary.  I go into this in a lot more detail throughout this site, but the bottom line is that if your contractor is using the correct chemicals then no surface agitation should be required.  You simply spray on the chemical with the help of a non-pressure pump, allow several minutes for it to kill the algae, and then rinse gently with a garden hose.  The only rare instance where a power washer might be useful is with very thick, green moss, but if all you have are black algae roof stains then you should have no need for scrubbing or power washing.  Make the mistake of cleaning your roof with high-pressure or aggressive agitation and you will probably only shorten its lifespan.  Use the right roof stain remover without pressure and you will extend your roof’s lifespan.

Roof stain removal doesn’t have to be complicated, but it is so important that you do it the correct way or hire someone who knows how to do it properly.  It’s very possible that you’ve had some so-called “expert” try to convince you that chemical roof cleaning is “bad” and will destroy your roof, gutters, and plants but it just isn’t true.  I’ve performed so many roof cleanings with chemicals alone that I could practically do it in my sleep, and I’ve never once had a situation where we caused damage to a home.  All we’ve ever done is ADD years to a roof’s life, not subtract them.  I can’t say the same for someone who relies on pressure or scrubbing, however.  Either you can take my advice or toss it aside, but don’t blame me when you decide to hit your shingle stains with a power washer and notice afterward that there are literally piles of shingle granules sitting in your gutter and on the ground.

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Roof Cleaners – The Checklist

So you’re finally ready to hire some professional roof cleaners.  Your spouse is complaining that the black roof stains are ruining your curb appeal, and after reading through this site you now understand that it’s also an issue of your roof’s health and longevity.  Now you need to know how to find a roof cleaning company that will do the job right.  Here’s a general checklist for what to look for in a contractor that cleans roofs.

  • First and foremost, you would be wise to find a roof cleaning service that uses non-pressure methods for roof stain removal.  If you’ve been digesting the other reading material on this site you should know by now that high-pressure roof cleaning is generally not a great idea.  The only rare exception could be in situations where there is very thick green moss like a carpet on your roof, and even in this extreme situation the pressure should be used carefully and responsibly.  Educated roof cleaners know that in the vast majority of cases, black roof stains can be completely and safely removed with the gentle application of a bleach or chlorine-based solution followed by a non-pressure rinse.  If you come across a contractor that wants to clean your roof with a high-pressure wand, run in the other direction as fast as possible.
  • Find a roof cleaning service that operates in teams of two Roof Cleanerson every job.  Theoretically, a roof cleaning could be done with one person, but the ideal scenario would be to have two roof cleaners on site for your job, one to apply the chemical and do the rinsing at the roof level, and the other to remain on the ground for perimeter rinsing and just as a “safety valve” in case the roof-man needs assistance.
  • Roof cleaners that have been in the game for any length of time know that your whole roof should be cleaned, not just the areas where black stains are visible to the naked eye.  If you can see stains in any one area, that’s usually an indication that algae is already taking hold over your entire roof and will just require a little more time to become completely visible everywhere.  Best to clean the whole thing and start with a clean slate, so to speak.
  • Ask to make sure that the contractor has liability insurance.  This one’s a no-brainer for any home improvement job, of course.  It not only protects you but it helps to weed out the handyman types who probably don’t understand the proper methods for roof cleaning to begin with.
  • Though this last one isn’t a necessity, you might check to see if the roof cleaner is BBB accredited.  If so, that’s usually a good sign that they have been around for awhile and are truly knowledgeable about roof stain removal.  If they aren’t a member of the BBB then ask for a few references that can vouch for them.  It’s also a good signal if they have their own before and after pictures to show off, either on a website or in a portfolio.

So there you have it.  Follow this list and you should be very happy with the results.  Ignore it at your own risk.  By the way, we have an ever-growing directory of professional roof cleaning services on this site for your convenience.

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Partial Roof Cleaning Not Recommended

Roof stains usually first appear on the northern-facing areas of a roof surface, as you’ve no doubt noticed.  This is because these areas receive less sunlight in the Northern Hemisphere (it’s the other way around in the Southern Hemisphere, as roof cleaners in Australia could attest to).  Sunlight aids in drying out the southern-facing slopes much more quickly after a rain, and since roof algae growth is accelerated by moisture, you can see how sunlight plays a role.  Direct UV rays from the sun also aid in retarding the growth of algae on these surfaces.

Roof CleaningHowever, it’s important to understand that even though the sun helps to slow the growth of algae on southern-facing surfaces, it does not stop it.  If you have stains beginning to develop on the northern-facing surfaces of your roof, it means that it’s just a matter of time before the entire roof is covered with algae stains.  You might not yet see black stains on the southern-facing surfaces, but that doesn’t mean that algae hasn’t already taken root and begun to multiply in these areas.

That’s why it’s a good idea to have the whole roof surface cleaned, even though it may appear that stains are confined to one side of the roof.  If you can see it somewhere on the roof, that means it’s everywhere on the roof.  You can demand that your roof cleaning contractor only cleans the area where you can actually see black stains, but don’t be surprised when, 12 months later, that area is still clean but the rest of the roof is suddenly covered in now visible black algae.

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Roof Cleaning Safety Products For The DIY Enthusiast.

You all should know by now that I discourage DIY roof cleaning because of the hazards involved, but I know that some people will attempt to do it anyway.  So I wanted to throw together just a short list of safety products for roof cleaning that many of the pros use (yes it can get expensive to buy all this stuff but roofs with slippery chemicals on them are a recipe for disaster if precautions aren’t taken (don’t say I didn’t warn you)).

  1. Get some Cougar Paws – amazing traction.  The grip on these shoes is so good you’ll feel like spiderman (or a cougar, I suppose).  In fact it is so slip-resistant that it can almost give you a false sense of security.  Wearing good shoes does not mean you can turn your brain off.
  2. Wear jeans or long pants.  No matter what chemicals, products, or procedures you’re using some of the stuff is bound to get on you, and better it land on denim than skin.  Of course whatever does get on your skin should be rinsed off immediately.
  3. Wear latex gloves.  Cheap dish gloves from the grocery Roof Cleaning Safety Productsstore will work fine.  Again this will help in keeping chem off your skin.
  4. Wear goggles.  If most of this stuff is bad for your skin just imagine what it can do to your eyes.  If something does splash in your eyes flush them immediately!
  5. Wear a respirator.  You DO NOT want to get the fumes from this stuff in your lungs.  Trust me.  Make this a priority.  Getting dizzy from exposure 45 feet off the ground is playing with fire, not to mention the potential long-term effects of repeated close-range exposure.
  6. Use a fiberglass ladder if possible to minimize the possibility of electrocution from bumping a power line.
  7. You’d be wise to invest in a roof harness system if you’re uncomfortable or unfamiliar with heights, ladders, or roofs in general.  Heck, everyone would be wise to use one.

Sounds like a lot, right?  Why not do yourself a favor and just hire a professional roof cleaning service like our friends at Safe Roof Cleaning, who already have the equipment and know-how to do it right.  Considering all the chemicals and gear you’d have to buy to do it yourself it would probably be cheaper to hire roof cleaners anyway, so why wouldn’t you?  Even if you think that it might save you a few pennies to do it yourself, is it worth it when the potential risks include paralysis or death?  I want to say this one more time to make it perfectly clear:  chemicals or water on a roof will render it EXTREMELY SLIPPERY (think ice), so you better be prepared if you’re a hard core DIY guy.

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