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How Much Does Cleaning a Roof Cost?

Roof Cleaning Prices

If you have an older roof, chances are good that you've noticed some discoloration or staining on it. These black or dark green patches, aside from being unsightly, can in fact damage your roof by stripping it of its protective outer layer and inviting the growth of further-damaging roof lichens and moss. Even if your roof is relatively new it is susceptible to roof algae, especially on the north side, where it receives the least amount of sunlight. To ensure that the harm to your roof does not become more widespread and necessitate roof repair or even replacement, consider investing in a roof cleaning.

Roof Cleaning Basics

The stains on your roof are probably caused by a type of algae known as Gloeocapsa Magma. Transported through the air by spores, Gloeocapsa can grow on any type of roof in any climate, though it is more prevalent in the Gulf States and other areas with warm, humid climates. And because asphalt shingles are the most common roofing material in America, more homeowners seek information about how to remove algae from asphalt.

While chlorine bleach solutions (consisting of one part bleach to three parts water to one part Tri-Sodium Phosphate) are often used by homeowners to address roofing discolored by algae, this approach is not without limitations. First of all, bleach can be damaging to plant life and other parts of the building and must be applied and removed carefully. In addition, a solution that is too strong or left to sit too long on the roof can damage the roofing material, especially asphalt shingles. Also, cleaning algae with bleach solution is often only a temporary solution. In time, the damaging growth can return, sometimes even strong than before. And finally, some homeowners make the mistake of rinsing off the solution with a pressure washer, which can strip asphalt of its protective granular surface.

To avoid DIY roof cleaning mistakes, consider hiring a professional. In addition to using proper techniques, professional roof cleaners can recommend biodegradable cleaners that pose no risk to the environment or your family's health. They can also apply products such as zinc strips, which are applied near the apex of the roof and ridge caps and release a protective zinc coating during precipitation, and anti-growth sprays that will keep damaging spores from taking root in the future.

Another thing to keep in mind is that if your stained roof is nearing the end of its lifecycle and needs replacing anyways, you can install a new roof made of algae resistant shingles.

Roof Cleaning Average Costs

The actual cost of roof cleaning depends on your location, the complexity of the job (i.e. roof size and pitch and the height of your home), and other factors. The following prices are only general estimates.

  • On average, roof cleaning pricing is $.15 to $.30 per square foot, or $15 to $30 per square (a square, in roofing terminology, is equal to 100 square feet). For an average-sized roof of 1,500 square feet (15 squares), that's a total cost of approximately $250 to $500. On a 2,500 square foot roof, expect to pay $375 to $750.
  • A 50-foot roll of zinc strips costs $25 to $50 plus the cost of installation.
  • Algae resistant roofing shingles cost around 10-20 percent more than standard asphalt shingles.