The HOA recently sent notices to several homeowners stating black algae stains are a maintenance violation that requires mitigation (cleaning). These black stains typically occur on north facing roofs (receives little sunshine and can remain damp for long periods) and are caused by an airborne algae (type of mold) that is endemic to the east coast from Florida to New England. Once a roof is affected, the spores can literally spread from home to home. There are several remedies not the least of which is roof replacement (ouch). There are also several products and countless businesses that claim the offending spores and resulting stains can be removed. Here are the remedies:

  • Roof replacement: the most expensive remedy and may not be required. If roof replacement is contemplated, be sure you select a grade of shingle that has a stain resistant agent built into the shingle. These usually have a 10 year stain guarantee.
  • Bleach solution: may be ineffective unless washed with pressure. Too much pressure can damage the shingles.
  • Chemical solution: can be toxic to plants, animals and humans. BE CAREFUL with these.
  • Roof cleaning companies: may be effective but be careful if they use toxic chemicals or claim they can pressure wash. You may end up with more damage than the stains were worth.
  • Environmentally safe cleaners: one such solution called Spray and Forget claims one application will kill the algae and remove the stains. However, the treatment depends on natural occurring elements to provide the cleaning action (like rain) and takes from 3 to 6 months to completely remove the stains. Do-it-yourself kits are available or you can hire a roofing contractor to apply it for you. Loudoun Valley Roofing in Purcellville provides this service for about $20 per 100 square feet of roof surface treated.
    Spray and Forget Brochure

So, if you get one of these letters, you now know what your alternatives are to become compliant.