Non Pressure Roof Cleaning

Roof Cleaning without damaging your shingles

Before and After


Do you ever look up at your roof and wonder just what those dark stains are? Where do they come from? Why don’t they disappear when it rains? Do they reduce the life of my roof? Most homeowners accept it as dirt, mold, or grime that comes with an aging roof.
The staining on your roof is an organism, the technical name being gloeocapsa magma, but more commonly referred to as algae. It is the most prevalent organism found growing on asphalt roofs all over the country, along with other organisms such as mildew, lichen and occasionally, moss. It survives by feeding on the limestone fillers used in the production of asphalt shingles. It arrives on your roof as an airborne particle, establishes itself, and then begins to grow, spreading where conditions suit. As it grows, you really begin to notice the black streaks across your roof.

Algae needs food, moisture, and heat to survive. You will find it growing mainly on the north facing and shaded areas of your roof where the lack of sun allows moisture to dwell. Take a look at the roofs around your neighborhood. Often, homes on one side of the street will have the black algae staining on the roof, while the roofs of the homes on the other side of the street appear to be clean. The dirty ones are probably facing due north and the ones that appear clean are facing south. A south facing roof gets a lot more sun which makes it a less conducive environment for the algae to grow. If you look at the back side of these homes, where the roof faces due north, you will more than likely see algae staining.

Algae doesn’t only grow on a north facing roof. We see homes with many trees surrounding them where algae have covered every roof pitch because of the abundant shade. There is some debate about the actual damage the algae does as it feeds, most experts agree that it is does some damage and creates additional problems discussed later in this article. One thing is sure; a stained roof detracts from the curb appeal of your home. This is an important consideration when placing your home on the market for sale. A stained roof can negatively impact the impressions of a potential buyer about the home and how it has been maintained over time.

Roofs are designed to protect your home from the elements. Asphalt shingles, by design, have hard reflective surface granules, which protect the shingle and aid in reflecting the sun’s rays to keep your home cooler. When your shingles are covered with these black stains, the reflective properties are diminished and your roof will retain more heat. The warmer a roof is, the more thermal expansion and contraction it is going to experience resulting in diminished shingle life. A warmer roof heats up your home making the air conditioner work harder to keep the temperature at the desired level than otherwise would be the case, which means higher energy bills.

The good news is that most of the time you don’t need to replace your roof. Asphalt shingles can usually be cleaned using low pressure or non-pressure cleaning methods approved by the Asphalt Roofing Manufacturers Association also known as ARMA. The cleaning methods listed in this technical systems bulletin, were approved some years ago and they are the gold standard for the roof cleaning industry. With all the competition in our industry, companies are doing their best to come up with new marketing terms. Do not be fooled by all the terms you see on the internet for roof cleaning. Here are a few: “Low Pressure”, “No Pressure”, “Non Pressure”, “Soft Washing” “Zero Pressure”, “Gentle Pressure”, “Certified”, “Patented Process”, “Green”, “ECO Friendly” It is all the same process being marketed differently. We want people to know; cleaning an asphalt roof involves a LOW PRESSURE application and LOW PRESSURE rinsing of the chemicals. Nothing else! It is that simple. Most roof cleaning companies use small, electric pumps or air pumps to get the chemical gently onto the roof.

99.9 percent of all professional roof cleaning companies use these non-pressure methods to apply sodium hypochlorite (basically bleach) and some type of surfactant (basically soap) in order to clean a roof. As it is the only method approved and endorsed by the shingle manufacturers, any company that deviates from it will certainly have trouble obtaining insurance in the industry. Now, there are a few companies out there that use pressure washers to clean a roof, you can read about that here, but the market has a tendency to weed them out after a year or so. Never, ever let a company tell you that using a pressure washer is an acceptable way to clean a roof. The use of pressure on a roof was the method originally used to clean roofs many years ago. It died out quickly once ARMA came out with the new standards, but some companies, in an effort to be different, have revived it and are marketing it as the newest, safest way to clean a roof. Don’t be fooled. If a company tells you that they do not use bleach, it is almost a certainty that they use a pressure washer and need a good amount of pressure to rinse the chemicals off the roof. It is an unacceptable cleaning method and may damage your roof.

ROOF REFRESH is licensed and insured professional roof cleaning and pressure washing company. We serve Raleigh, Cary, Apex, Garner and Wake Forest NC and we specialize in roof stain removal. We use only safe, ARMA approved, non-pressure cleaning methods to gently remove roof stains and we offer a 3 year, no hassle warranty against their return. Visit our website at for more information or give us a call 919-291-2717. We will be pleased to come and look at your roof and give you a no-obligation estimate. Don’t forget, we also offer low pressure house washing and driveway and walkway cleaning.

Roof Refresh

September 3, 2012