Roof Cleaning: Everything You Need to Know

Roof Cleaning: Everything You Need to Know

Is Roof Cleaning a good idea?

Roof Cleaning: Everything You Need to Know

In short, yes absolutely. However, to answer this question effectively it is best to understand what happens to roofs over time and why they need to be cleaned.

Why do we take care of roofs?

Roofs come in many types of material: metal, shingle, tile, and more. Regardless of type, they are exposed to the elements every second of each day and see every bit of the harshest weather conditions you experience. They do a great job at protecting your biggest investment: your house and belongings. Roofs are large and expensive to replace, so it’s important to maintain them to ensure you get the most life out of them you possibly can.

What happens to roofs over time?

Roofs come in many types of material: metal, shingle, tile, asphalt, and more. Regardless of type, they are exposed to the elements every second of every day and see every bit of the harshest weather conditions you experience. They can all be cleaned pretty much the same way, with specific care being taken depending on the material. Since roofs are a horizontal surface with some slope, they retain water longer than vertical surfaces such as walls and siding. This introduces an opportunity for lots of organic matter to grow, especially when shade is part of the equation.

What grows on your roof?

Lots of organic matter will take advantage of this wet, shady environment. Even if there are no trees around, the sun is not always shining to prevent the growth of substances such as moss, algae, mold, mildew, and lichen. These are the most common types of growth that occur on roofs (and siding!), and can be detrimental to the quality of your roof over time.

Mold and mildew are easily spotted on roofs and can be identified by dark areas and black streaking, especially where water leaks off the side of the roof or below vents or structures protruding through your roof. These can eventually spread to inside the house, causing air quality issues and health hazards and should be addressed immediately.

Algae is very common to see on roofs as well. While extremely visible on metal and tile roofs, it can be easily identified on shingle roofs as well through patchy areas of green or even whole sections of green algae growing. While not as serious as mold and mildew, algae is rather unattractive and can damage your roof’s surface over time if left unattended.

Moss is another common culprit found growing on roofs. We all know moss as the bushy green patches that grow in dark, moist areas. This is most commonly found on roofs that have lots of shade during the day. Moss must be treated because it not only retains extra moisture to harbor growth for other matter, but it also grows on the edge of shingles. From there it grows up underneath the shingle or tile for extra moisture retention and protection and lifts the shingle/tile, eventually removing it from the roof. We have an excellent way to treat moss growing on roofs.

Last but not least is the Lichen. Lichen on a roof is just plain gross and unattractive. It is identified by it’s flat, almost leafy appearance and is typically green or light gray in color. It is most often also found on roofs that receive a lot of shade throughout the day and should be treated regularly.

Can you scrape organic matter off your roof?

Finding a way to scrape organic matter off your roof poses lots of problems. This would not be a good idea because it likely involves you or someone being on top of the roof, which is dangerous. Scraping any material off your roof is likely to also damage your shingles, whether they be tile, asphalt, or even a metal roof. Scraping a roof would take much more time, and also be much more difficult and unlikely to get the surface completely clean. The safest, most complete, and most efficient way to clean your roof would certainly be by using a chemical treatment applied from the safety of the ground or on a ladder utilizing a ladder stabilizer to prevent any falls.

What is the best way to have a roof cleaned?

Treating organic matter growing on roofs is a dangerous task and should certainly be left to a professional. One of the biggest safety factors in treating these is being on a roof. Homeowners walking on their roofs can be very dangerous and can propose the opportunity for slips and falls to happen. It is also unsafe to spray any type of liquid or chemical on a sloped walking surface, as it will become very slippery.

When you hire a professional roof washing company, they are equipped with the appropriate safety gear, ways to access the roof, and insurance in the event something goes wrong. Many times they are even able to apply their special chemical treatment from long range from the safety of the ground or a ladder, eliminating dangerous safety hazards and allowing the roof to be cleaned efficiently and effectively from the safety of the ground.

Does roof cleaning damage your roof?

No it will not. If your concern is high pressure damaging your roof, read on. Roof cleaning is performed with a method called soft washing, which uses little to no pressure. A chemical treatment is applied and either lightly rinsed off or left to dry. There is no damage caused by high-pressure washing of your shingles, insurance companies would not like that! Sometimes Tile roofs can be pressure washed as well as soft washed, but usually chemical treatment alone does the trick.

Is roof cleaning safe?

Roof cleaning is absolutely safe when performed by professionals with the right equipment and know-how. A treatment is applied to your roof and either left to dry or rinsed off depending on the material. If left to dry, it will remove and prevent organic matter from growing back any time soon.

How long does a roof cleaning take?

This depends on what type of material your roof is. Typically a treatment can take anywhere from one hour to up to eight depending on the size and complexity of the roof being cleaned. Metal and tile roofs are typically rinsed off once the organic matter is treated which can take longer. For heavy soiling on roofs covered in moss and lichen, the treatment will typically be left on to dry and within a few weeks the remaining moss and lichen will die and fall off. Each time it rains the roof should be slightly cleaner.

How often should you have your roof cleaned?

Homeowners should have their roof cleaned as frequently as every year or as soon as they notice organic matter growing back, especially mold and mildew. Doing this ensures your roof will last as long as possible to protect your precious investment.

When is the best time to have your roof cleaned?

The best time to have your roof cleaned would be when the organic matter is actively growing. Moss, lichen, and algae usually grow the most in the fall and spring time when there is not as much hot sun shining on them and they can retain moisture longer. Depending on where you live (in the north or south), you should plan to have your roof cleaned when it is not very hot outside, and the temperature is cooler so you can be sure that your organic matter is alive and growing rapidly.

How much does roof cleaning cost?

Roof cleaning is a service that should always be performed by professionals with the appropriate know-how and equipment. Doing so ensures a complete job done in a timely fashion. When pricing roof cleaning, you can expect to pay anywhere from $0.25 to $0.65+ per square foot of living space. Some factors that can determine price include ease of access to parts of the roof, the pitch of your roof, as well as whether your house has gutters or not. Houses without gutters may or may not be able to be cleaned, as the runoff treatment risks damaging vegetation or belongings beneath. Prices vary from area to area.

Benefits of roof cleaning

By now you have read most of what roof cleaning has to offer. Having your roof cleaned greatly increases the curb appeal of your home and also extends the life of your roof, especially if you have lots of moss growing on it. It also prevents safety hazards and air quality issues in and around your home by treating mold and mildew growing on it.


Roof cleaning is a very safe and effective method of ensuring your roof lasts as long as possible and looks it’s best. Organic matter loves growing on roofs and proposes many detriments to both the homeowner and roof surface (plus neighbors if we’re counting curb appeal). Professionals have the safest, fastest, and most effective way to get your roof cleaned and working optimally and should be done yearly to ensure optimal roof life and appearance.

If you are looking for a pressure washing company, then please call Nashville Clean Windows & Pressure Washing 615-669-8098 or complete our online request form.


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