You need your roof washed. Perhaps there are black streaks on it, or moss and lichen. As you search the internet looking for a professional to clean it you come across a myriad of terms “soft wash”, “low pressure”, “roof shampoo” and “eco-friendly”. You’re bombarded by dire warnings like “Did you know your roof is not dirty at all, it’s infested.”, “roof mold (fungi) and algae can pose a health danger and are harmful” or they’ll give you a lifetime guarantee against stains as long as you do their annual stain protection program.
As someone who cleans roofs it’s very disappointing to see the scare tactics, misleading information and just plain malarkey permeating the internet. I’ll explain about roof cleaning, but you make up your own mind where the truth lies.
Can high pressure can ruin a roof? Absolutely, but just because you use a pressure washer it doesn’t mean you’re blasting it off at full throttle. Professional pressure cleaning equipment can have a variable speed. It can be so low that the water mists out, or it can be so powerful that you can sign your name into wood siding. What’s important is the experience the person has behind the equipment. So maybe the question to ask of the person quoting your roof would be “Do you have a variable speed machine and what volume of water can it produce?” and “How much experience do you have?” or “Have you done any work I can drive by?”
Will bleach (sodium hypochlorite) ruin my roof? No, bleach will not ruin your roof. Do you know what manufacturer made your shingles? Go to their website and look up what they recommend for cleaning their product. For instance, GAF is one of the big manufacturers, they have a technical advisor bulletin. Here’s the link.
In it “GAF recommends cleaning the roof with a special mixture of 4 gallons of water with 1 gallon of bleach and 1 cup of TSP (tri-sodium phosphate).”
Or how about the Asphalt Roofing Manufacturer’s Association. Here’s the link.
Here they say “Solutions range from one cup TSP, one gallon bleach and 5 gallons water, to one cup TSP and 2.5 gallons each of bleach and water.”
What I take from this is… if the leading roof manufacturer and the leading roof manufacturing association both recommend using bleach, then maybe that’s what should be used to clean a roof. Maybe the question you should be asking when you see statements to the contrary is… “Are they trying to sell me something?”
Can lichen and moss can shorten the life of your roof? Yes. Both lichen and moss will grow into your shingles. They can lift the edges up as they grow. They will loosen the granules. We know we need to get it off, but how. Some companies will shoot a solution of bleach on the roof, this will kill it, but it still has to be removed. High volumes of water (not high pressure, that’s different) will push it off the roof. Sometimes if it’s really bad you have to sweep it off. Do we really want to do that, no, but if you waited eons to take care of the problem, then that’s what may have to be done.
Will those black streaks shorten the life of a roof? Well, maybe, but I haven’t found any proof it does. It is ugly and we get quite a few calls to clean it off and if curb appeal is the reason you’re doing it, that’s fine. But if someone is scaring you saying it’s a health hazard, you can still get it cleaned, just go with someone less histrionic.
The no rinse method. Really? So someone quotes your roof and says they’re going to spray the chemical on your roof and leave it. That it will come off with the next rain. Ask yourself “Do I think leaving a chemical on my roof really won’t damage it.” You decide.
I saw someone guarantee a roof from algae. A good roof cleaner can get all the mold and algae off your roof, but right after it’s done spores from your neighbor’s house are already landing on yours. The guarantee really is you won’t see the black streaks come back for a few years because it takes a few years for it to build up to that point.
I got a few quotes and noticed that some of these guys are certified. This means nothing. The companies offering the certifications are for profit businesses. There are not any recognized certifications in the industry. These are website businesses that have popped up as the roof cleaning industry has emerged. Jump through a few hoops and pay a steep price you can use their “certification” logo.
Why do roofs need to be cleaned now? I don’t remember this being done years ago. The quality of manufacturing materials has changed. I’ve been in business since 1985 and roofs really didn’t have the problems they have now. It was rare that a roof needed to be cleaned. Unfortunately, over the years the manufacturing process has changed. There is more limestone and fillers in the shingles now. Algae, Gloeocapsa magma, feed on these additives. It’s typically this algae that you are seeing on your roof causing the black streaks.
Will my insurance company drop me if my roof is dirty? I haven’t come across that myself, but here’s a link to a NBC new story. Oddly enough though we’ve gotten calls from homeowners asking if we can clean their roof quickly because it didn’t pass inspection when they were trying to sell it. This past weekend one call was because the buyer was having the outside of the house tested for mold to the tune of $1,200. I can’t imagine anything outside not testing positive for mold. The real danger of mold is when it’s growing inside your home, this can be caused by a leaky roof or other water issues.
What are these terms we see like “soft wash”, “low pressure”, “no pressure” and eco-green”? “Soft wash” and “low pressure” are terms used so the customer understands that the high pressure that can damage a roof is not being used. “No pressure” usually refers to someone who will spray your roof with chemicals and leave it there till the rains takes it off. “Eco-green” has popped up in conjunction with cleaners that do not contain bleach (sodium hypochlorite) but use hydrogen peroxide and sodium bicarbonate (baking soda) in them.
Can I clean my own roof? I really don’t see why not. If you’re comfortable with the height and you have a low roof that’s easy to access then try what your roof manufacturer suggests. Don’t use a pressure washer as the one’s sold or for rent in the big box stores will not have a variable speed wand and even though they are only a fraction of the power of a professional pressure cleaner it will still be too much pressure for shingles. If it’s bad you may want it done professionally the first time then you can “keep it up” by doing it yourself after that.
When do I want to hire someone? When you don’t want to do it yourself, if it’s too high, steep or dangerous. If it’s really dirty or has moss and lichen on it. If it’s an old roof or you’re old.
What cleaning methods do you recommend? We’ve been doing roofs since 2000. We use a low pressure system and 12% sodium hypochlorite (a bleach that is stronger than what is in grocery stores) with a surfactant. The surfactant is an additive that causes sudsing, like detergent does. Using this keeps the chemical on the roof instead of running off it. The bleach needs to stay on the roof long enough for it to kill the algae, mold, moss or lichen. If your roof is bad, we repeat the process. That’s another one of the drawbacks of the “no rinse” guys…you may have to call them back as they leave before they know it worked. We know when we leave it’s clean. Our machines can handle large volumes of water, remember the difference between high pressure and large volumes of water. You can have a machine that can only put out 3 gallons a minute, but will damage a roof, where a variable speed machine can put out 6 or more gallons a minute and be perfectly safe. It all has to do with experience and technique. We also pre wet any plants and keep rinsing them off to prevent damage.
Being in this industry for so long I’ve seen a lot of hype, new chemicals, new techniques, new organizations and newbies in business. Some days I become so frustrated, and even embarrassed to be associated with this business because of posts I’ve read on professional online boards I’m part of, or by going on other people’s websites and seeing horrendous scare tactics being used. I’m an old school kind of guy…I do an honest days work for an honest day pay, and I take pride in the work I do. Take heart, there are a lot of reputable guys out there. Unfortunately for you, the consumer, there’s a lot of bullshit to wade through to find them.