If your roof is on your spring-cleaning checklist, good for you, good for your roof and for your wallet. Ridding your roof of infestations, such as black algae, mold, moss and/or green lichen blotches, is essential to maximizing roof performance and service life and avoiding expensive repairs. Use caution, however, and use this guide of the do’s and don’ts of cleaning your asphalt roof so that you don’t inadvertently cause more harm than good to your roof and your safety.


Roof stains are not only unsightly to the extreme, the organic growths infesting your roof may be causing damage as they feed on the organic compounds in the shingles and underlying roofing materials. In fact, shift your perception of roof “stains” to a roof “infection” caused by bacteria, fungus, lichens, algae and/or moss. If you don’t eradicate these leeches, so to speak, your roof and wallet are going to suffer.

With this shift in thinking, you can approach cleaning and curing your infected roof akin to treating a sick plant or infected tree, rather than to washing your clothes, car, carpets and walkways. There’s a big difference.


  • Pressure washing: Water streaming out of a pressure washer can exceed 200 MPH — faster than any recorded hurricane. Pressure washers can loosen, uplift, tear and dislodge shingles, and remove protective granules. Do not allow anyone to clean your asphalt roof using a pressure washer.
  • Harsh chemicals: Don’t take any shortcuts in cleaning your roof. It’s true that bleach will kill any plant life it comes into contact with — including your landscaping. You wouldn’t treat a sick plant or tree with bleach and phosphates, right? Bleach will also react with and corrode the metal parts of your roofing system, such as the flashing, boots, valleys and gutters.
  • DIY vs. professional cleaning: It is never recommended for the homeowner to climb up on the roof. It’s too dangerous. In fact, roofing is consistently one of the top 10 most dangerous professions in the country.


  • Eco-friendly solution: Make sure your roofing professional uses only environmentally-friendly cleaners to clean and cure your sick roof.
  • Tree trimming and debris removal: Trim back or remove overhanging tree limbs around your roof. This will help keep debris off your roof, help prevent damage during wind-driven storms and, more to the point, it will allow more sunlight to reach your roof, which helps prevent the growth of some organisms.
  • Gutters: Keep your gutters and downspouts in good working order and free of blockages. This will help keep your roof dry and protect your home’s foundation.
  • Hire a professional: Hire a licensed, bonded and insured roofing contractor to handle all of your roofing needs — including cleaning and treating your asphalt roof. You want to minimize the amount of walking that occurs on your roof and scrutinize the people you allow to do it.

If you have questions or need clarification of any of these points about cleaning your asphalt shingle roof, contact the roofing professionals at Welter Construction today!