The Right Way to Clean a Roof

The Right Way to Clean a Roof

By Target Roofing & Sheet Metal / Published May 2021

Photos courtesy of Target Roofing & Sheet Metal

Maintaining property values is a key responsibility for all community association managers. That means properties must not only look their best but also be properly maintained and kept in working order. This includes obvious items like maintaining the landscaping, pool equipment, amenities, and other common elements.

     What is often overlooked, however, is the roofing system. Many times, it’s out of sight, out of mind. If a roof is not leaking or has been replaced in the last five to ten years, association boards often assume all is well. Roofing professionals can affirm this is far from the truth. Studies by GAF, the world’s largest roofing material manufacturer, have proven roofs that undergo proactive annual maintenance programs last longer and have fewer expenses over their lifetime than roofs with just reactive repairs.

     A regular roof cleaning is a critical component of a good maintenance program. Any roof, whether it’s flat, metal, tile, or shingle, is exposed to the elements all day, every day. While rainfall can appear to wash off the appearance of dirt, a closer look reveals that most dark staining and streaking are actually caused by algae known as Gloeocapsa magma, or GM. These algae are bacteria that feed off asphalt and limestone commonly found in roof tiles and shingles. Essentially, algae are literally eating away roofing materials. Algae spores are easily transported by the wind and can quickly spread from rooftop to rooftop within a community.

     To clean roofs, property managers and property owners often tap two primary solutions, pressure washing and soft washing, but a third option—bio washing—might be better for both your roof and the environment. 

Pressure Washing

     Commonly called power washing, pressure washing can produce immediate, dramatic results on hard surfaces. Unfortunately, it’s also very taxing on a roofing system. Cleaning contractors often use spray guns exceeding 3,500 psi, which is so powerful that they can etch concrete or clay roofing tiles and blast protective granules right off asphalt shingles. In both cases, the damage can void manufacturer warranties and leave property owners responsible for the full cost of future roof repairs. Additionally, pressure washing only removes the surface layer of algae. While that makes a roof appear cleaner, it does not kill the underlying algae that cause staining and damage. It’s similar to trees after a windstorm—the leaves might disappear after a hurricane or tropical storm, but after a short while, they’ll all grow back.

Soft Washing

     Some roofing contractors recommend high-pressure soft washing systems as the safer alternative to clean a roof. However, there are still some concerns to keep in mind. Soft washing uses toxic chemicals to clean. Harsh chemicals like bleach, phosphates, or copper sulfates can quickly kill algae and generate instant results. However, these chemicals are very hazardous to residents, their pets, and the association’s landscaping, lakes, and ponds. 

Bio Washing

     There are also gentler, earth-friendly washing alternatives that use products like Citra-Shield™. The biodegradable formulas may not create an instant “wow” factor after being applied, but within days and weeks, they will generate the desired results while offering peace of mind that residents, pets, and the surrounding environment will be safe. Citra-Shield™ kills mold spores and algae growth at the root, and roofs will stay clean much longer than roofs that have only been pressure washed or soft washed. The black or green stains are removed over time with waves of rinse cycles from Mother Nature’s sun, wind, and rain once the active ingredients have shriveled the root and spores with the time-release system.

     Property managers and associations often turn to cleaning companies and preferred vendors for annual jobs like this. These companies can effectively clean sidewalks, building exteriors, and driveways, but roofs are different for many reasons. First, roofs are designed to withstand punishment from natural elements, but not pounding from foot traffic. Licensed roofing professionals know how to walk on a roof without damaging it. Experienced cleaners who are inexperienced on the roof can very easily cause significant damage. Second, reputable licensed roofing companies carry stronger general liability and workers’ compensation insurance policies that cover repair work performed at higher elevations; many exterior cleaning vendors do not have that level of coverage. Third, hiring a licensed roofing professional provides peace of mind knowing your roof is in good hands and you won’t have to address any unexpected liabilities.

     There are a multitude of reasons that illustrate the importance of selecting a qualified roofing maintenance program that includes roof cleaning. Not only will it extend a roof’s life span and keep warranties valid, but there is also a human side to the decision. An under-researched choice can affect the health of community residents, their pets, and the environment when selecting an unqualified roof cleaning service. Employ-ing a licensed roofing contractor to clean roofs ensures that an experienced professional is always looking out for you. 

Target Roofing & Sheet Metal

     Target Roofing & Sheet Metal is a licensed and insured commercial roofing specialist headquartered in Fort Myers. For more information, please visit or call (239) 334-7496.