How to Clean Moss from Your Roof the Right Way

The roof over your home is one of the most valuable assets of your house exterior. Whether you have shingles, barrel tile, or metal roofing, a properly installed and maintained roof diverts water flow away from the home, is leak-proof, and should last you many years. Just like your house siding, driveway and windows, your roof requires some level of maintenance cleaning to keep it from accumulating mold and algae growth, or even worse, moss formation.

Mold growth on roofs in the most common contributor to premature decay of asphalt roof shingles. Gloeocapsa magma is the main species of mold that grows on roofs and is most seen as “black streaks”. These black streaks are not only unsightly, but they eat away at the limestone in your shingles and cause early decay.

Even worse than mold growth on roof shingles is moss growth. Moss also contributes to roof damage in several ways. Moss is an organism, so it absorbs water like any plant, which can be absorbed up under the shingles where moss is growing, causing water damage to the internals of your home. Secondly, moss growth can cause shingles to warp and dislodge, further contributing to water damage.

Moss removal is tricky and should only be done a certain way. Like any professional company would do, we recommend following manufacturer guidelines or those from a professional organization. We clean moss from roofs following direction of the Asphalt Roofing Manufacturers Association (ARMA). Below, we are going to outline some common ways that people believe shingle roofs can be cleaned and discern to you whether or not they are the correct way to clean roofs. By the end of this article, we hope you feel confident in taking on your own asphalt shingle roof cleaning!

Roof Cleaning with a Pressure Washer (NEVER DO THIS)

We want to get this one settled right out of the gate. NEVER pressure wash your roof. Not only will this damage your roof right from the start, it violates any existing warranties offered by the installer of the roof. Pressure washing roofs can cause accelerated granule loss, dislodge shingles, put water up under the shingles, and cause leaks on the inside of your home. No need to rent a pressure washer or dust off the one you hide in the corner of your garage. Stay far away from them when it comes to roof cleaning.

Moss Removal with a Brush (SOMETIMES do this.)

Roof cleaning using a broom or brush can come in handy in one of two scenarios. The first being, if your roof is ENTIRELY COATED in a thick bed of moss, it is sometimes required to brush off most of it before applying a cleaning chemical to kill the moss at its roots. Just be wary in this approach, because brushing or brooming moss off roofs can cause accelerated granule loss or dislodge shingles if you are too rough in your approach. Be gentle and avoid if possible.

The second scenario is once you have treated your roof shingles with a biocide that kills moss (which will be discussed in detail below), wait 5-6 months and see if it falls off naturally. If there are remaining tufts of moss, you can lightly brush the moss off and see if it crumbles away easily. If it does not, treat the moss again using the methods below and wait a few more months.

Chemicals for Roof Cleaning

Now we are getting into the real deal of professional roof cleaning. Without any professional insight from us, you would likely be spinning your wheels trying to figure out what chemicals to use to clean your roof. There are a ton of opinions out there. Some people say using trisodium phosphate (TSP), some say sodium percarbonate, some say hydrogen peroxide. All these chemicals are effective in cleaning roofs to some extent, but all of them have obvious drawbacks that we as professionals understand but will not bother getting into. The most effective, cost-saving, and simple way to clean a shingle roof with moss on it is to use household bleach, also known as sodium hypochlorite.

Roof Cleaning with Sodium Hypochlorite

Removing moss with sodium hypochlorite is the method recommended by nearly every professional soft wash / pressure washing company, as well as the Asphalt Roofing Manufacturers Association. We are going to outline in detail how to treat moss safely and effectively from start to finish.

First, familiarize yourself with ladder safety and PPE. Watch some videos on ladder safety and look up the safety data sheet (SDS) of sodium hypochlorite (aka bleach) and get the right PPE. If you are not sure how to use sodium hypochlorite safely and effectively, as well as a ladder to reach your roof shingles, pass the work off to a professional company like ourselves. We can do it faster, safer, and more effectively, but we want to make sure you can do it yourself if you want to!

After getting a ladder and the correct PPE, get your remaining equipment, which should consist of a garden sprayer, garden hose, and an oscillating sprinkler. The garden hose and sprinkler will be used to keep all your landscaping saturated with water while you are cleaning so that the bleach solution does not damage the plants when it comes in contact with after running down the roof shingles. The garden sprayer will be used to apply the sodium hypochlorite mixture, which we will tell you how to make below.

How to Make Sodium Hypochlorite mixture for roof treatment: We recommend a solution that has a sodium hypochlorite concentration of somewhere between 5-6%. This can either be accomplished by buying household bleach, which is usually around 5%, or by buying pool shock and mixing it half and half with water. After putting the correct mixture in your pump sprayer, add 4-5 ounces of laundry detergent to help it stick to the roof shingles as you spray the roof.

Spray your roof singles top to bottom generously while the garden sprinkler showers the plants below you. Over the course of 10-15 minutes, the moss you are treating should turn from a dark green color to a white-tan color. Once all the moss has turned to the correct color, rinse off all your landscaping one more time. Now the moss should die off naturally over the course of 5-6 months, maybe sooner! Set a date in your calendar to inspect your roof shingles and re-treat areas as needed.

Conclusion

In this article, we have outlined how to effectively clean moss off your roof using just a few cleaning ingredients and garden tools. This method is effective for cleaning both moss and black streaks off your roof, making for a powerful combination of safe and effective cleaning. If you need roof cleaning in Raleigh, NC look no further and call our team at InTune SoftWash, LLC. We pride ourselves on being the Raleigh area’s top roof washing company. Our commitment to expert-trained technicians, quality work, and a 100% satisfaction guarantee makes us the choice for your roof cleaning needs. Give us a call at 919-420-4190 or fill out a quote request form on our website. We look forward to hearing from you!