An Article I wrote on Roof Cleaning

[Kevin Enderle]

This is an article I published on Linked-In and Nextdoor regarding Roof Moss, Moss Control and Roof Cleaning. Thought I might share it with folks here in WA since it is a necessity and one thing I see neglected on a LOT of investment properties. I can't help but look at roofs as I drive through the neighborhoods (side effect of the business!) and there are plenty of mossy roofs around here! Unfortunately, all to many people are simply unaware of what moss can do and the need to service the roof. The penalties for ignoring it can be pretty expensive. I've seen 30 year roofs with literally over 1/3rd of their lifespan cut short due to lack of maintenance. Professional Moss Treatment is relatively affordable...a new roof isn't.

And a serious note about safety. IF you are a DIY sort of person, PLEASE be safe on your roof! Mossy roofs are slippery and dangerous. Even a moderate pitch single story roof can get you. At the bare minimum you need a safety harness, ascender/descender or Rope Grab, need to know how to use and wear it properly, need to have a second person capable of reaching and assisting you if you DO get fall arrested and happen to go off the roof, and you need permanently mounted roof ridge anchors. No, a Tree or the hitch on your truck or your chimney are NOT good places to tie off. If you do NOT have safety anchors, we can install them for you.

Think this is overkill? I've had the unfortunate opportunity of cleaning a roof for a widower whose husband died after falling off the roof in Lynden. Another gentleman passed away here locally after failing from a ladder cleaning his gutters. Several of my employees lives have been saved by fall arrest gear. It is no joke.

Last but not least, if you are going to do it yourself, spraying the roof with a pump up sprayer, and a Backpack sprayer on the roof...No. Just NO. It just isn't safe. Far too easy to lose your balance and they leak. Unfortunately, most people do not have commercial grade spray systems in their garage. You can't rent them at Birch or Hardware Sales, they are too specialized. But...you can rent one from me! If you insist on DIY, then contact me for a spray system rental. Also good for doing decks and fence cleaning.

Now: On to the article!

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Keeping a good roof over your head is a universal desire. But here in the Pacific Northwest, we have things which fight our ability to have a nice roof over our heads. Specifically...Moss. Here in WA State, it *should* be the official state plant. Roof moss is ubiquitous and ever present. Here is what you need to know about what it is, what it does and how to treat it.

Moss is an ancient organism. It grows primarily in shady places with adequate moisture. Moss isn't a "plant" in the traditional definition. It does not have a vascular system and absorbs nutrients through its leaves.

Moss has no roots. Instead, it is similar to mold in that it puts down rhizomes, tendril like threads that latch onto or burrow into the substrate on which it grows. And like Mold, Moss does not have seeds. Instead, it grows from and reproduces through spores. 

Moss is a world champion of the "plant" world when it comes to holding water. Able to absorb and hold an eye popping 20 times its weight. It is these properties which make moss not only very very good at reproducing on your roof, but also make it so damaging.

The Rhizomes of Moss burrow into and bond with the granular surface of the roof and can and will penetrate the underside of the leading edge of the shingles on a roof. This strong hold down system is what makes it hold on tenaciously, and also is what makes it damaging. By bonding with and even burrowing into the roof shingles, the Moss loosens the granular structure of the shingle. Those granules are what protect the inner structure of the shingle from damage and drying out. Once the shingle dries out, it will start to crack as it is unable to expand and contract with changes in temperature.

Once moss gets under the leading edge of the shingles, it is here where the damage can really get bad. That ability to absorb all that water...and expand, makes the moss act like a jack. It can literally lift the leading edges of the shingles, leading to wind loss and water penetration. Don't believe that water can get in through this avenue? 15 years of experience treating attics for mold...or having to tell customers the roof is beyond saving says otherwise.

Getting rid of the moss is important before it starts to do some very expensive damage. A $399 moss treatment is a lot less expensive than a $10,000 roof replacement.

WHAT ELSE IS UP THERE?

There is more than just moss on your roof. There is literally an entire ecosystem. There are large cyanobacteria colonies which grow on your roof. They are what cause those black streaks you see on roofs. They should be removed as they are a great food source for the moss spores, literally starter food! I've cleaned a couple of black roofs which actually turned out to be white. The owner had no idea! Then there are lichens. Lichens are the death of a roof. We've seen them literally burrow through a shingle to where you could see the attic interior from the ridgeline. Proper professional cleaning products will remove these organisms.

MOSS TREATMENT VS ROOF CLEANING. What is the difference?

Moss Treatment is what I recommend for most roofs with light to moderate moss infestations. The moss is thoroughly sprayed with a treatment product to kill it. It will then desiccate, die, and decay. Once the root system decays the moss will release from the roof and be washed away. This is the safest process for the roof. On heavy infestations, we may need to do several treatments prior to...

Roof Cleaning. Roof Cleaning is a more active version of the above process. Instead of letting nature take its course, we actively remove the dead organisms. The Moss is sprayed with a solution which rapidly breaks down the root system. The entire roof is then rinsed with a low pressure rinse system to remove the moss. This is a far more labor intensive process which requires a lot of hours of labor on a steep roof. It is recommended for those who have insurance notifications (get rid of the moss or face cancellation), or for those planning to market their home (nothing shows better than a fresh, clean roof!). It is also good for those who have a requirement for financing during a real estate transaction as underwriters will often demand the roof be professionally cleaned. Finally, it is a good maintenance procedure which should be done every 5 or so years to keep the organic layers from building up on your roof.

HOW to treat moss, along with the other organisms which grow, is one of the most misunderstood subjects. The methods used are wide and varied...and many times wrong. Sometimes doing as much damage to the roof as the moss itself.

First up...Pressure Washing. Most people know that you shouldn't pressure wash a roof. But yet, there they are on the weekends. Homeowners and Craigslist Cowboys out there...pressure washing roofs. Blowing Moss off the roof with straight pressure damages the granular structure. We've seen pictures of entire roofs practically denuded of granules by bad pressure washers. And pressure washing does little to the other organisms on the roof, typically guaranteeing a rapid return. The roofing manufacturers say don't do it. Roofing Professionals say don't do it. Your insurance company says don't do it. Don't blast your roof! What else do they say you shouldn't do?

Brooming and Scraping. This is also NOT recommended. Why? The Rhizomes. Those hold down roots are bonded in with the roof surface and if you rip them off, you are going to loosen or even rip off the granules. That giant pile of granules in the gutter afterwards is your roof life literally going down the drain. It does nothing to remove the other organisms either.

Moss Powders. These are powders you can buy at the Home Improvement stores. Typically Zinc Sulfate. Homeowners or amateur contractors, known in the industry as "Powder Jockeys", will sprinkle them on along the ridge lines. The theory being the rain will rinse the powder evenly across the roof. There are two problems with this method. First, the coverage is NEVER even. Ever. Second, these powders set up a self perpetuating cycle. They leave behind a sticky organic layer on the roof. This acts as a fertilizer bed which leads to a huge bloom of algae and cyanobacteria. The next year, you will see exactly where the powder was spread because that area is often quite green. IF you are going to use this material, not recommended in any watershed areas by the way, then your best bet is to dissolve and spray it on.

Tide Detergent. This has very limited effects and causes an issue with sticky calcium carbonate. It is fine for your clothes but please don't put it on your roof.

Zinc and Copper Strips. These are effective...to a limited degree. The issues are several fold. First, they have to be placed approximately every 3 feet down the roof in order for there to be enough copper or zinc oxides. Second, they need to be replaced frequently as the majority of the products sold are *extremely* thin. Third, they either need to be slid up under the shingles, breaking the seal bond, or nailed to the roof. After a few years of replacement, your roof will start to look like Swiss cheese. I've seen tons of roofs infested with moss with a nice big fat zinc strip at the top. I've even seen moss growing ON the Zinc strips!

A good, professional cleaning or moss treatment product is generally not something you will find at a hardware or big box store. It is typically customized for the area and the conditions. It will be applied in liquid form so that all the surfaces are covered, getting the product to every part of the roof and saturated into every bit of the moss. It will also be effective at killing the other organisms infesting the roof. This often means getting onto the roof with a proper spray system and this is where the professional has the advantage. A professional will have a large commercial grade spray system designed specifically for applications of moss and roof cleaning solutions onto the roof and a safety harness system to get onto the roof safely. Chances are you as a homeowner or investor do not.

How Often?

This is one of the most frequently asked questions I get from homeowners. How often should I clean my roof?The answer is always the same...it depends. A house in open farmland without any trees in Lynden or the Skagit Valley is going to be different than a house in the trees in Sudden Valley. A good general rule of thumb is to do treatment every 2 years and a full cleaning every 5-7 years.

Catching Problems.

A good full service roof cleaning is also a great way to PREVENT roof problems. When you are up on a roof cleaning every square inch, it gives you as a contractor a good overall view of the roof condition. Spotting problems is a huge plus. We've spotted numerous soft spots, flashing issues, holes, missing ridge caps, cracked/loose vents, and cracked/missing pipe boots.

In conclusion, Moss Treatment and Roof Cleaning are important parts of property maintenance. They can help extend the life of your very expensive roof. They improve the visual appearance of your home, helping to maximize value and they help catch and prevent problems and keep your insurance intact. As long as they are done properly, they are safe for your roof and your home.