Never let a contractor on your roof with a pressure washing wand. Here's exactly why.
Modern asphalt shingles are coated in ceramic granules. These granules reflect UV rays and protect the underlying asphalt core from drying out, cracking, and leaking. When algae (black streaks) grows on your roof, it begins feeding on the limestone filler.
If a contractor uses a pressure washer to clean these streaks, the high PSI strips thousands of protective granules off the roof, washing them directly into your gutters. You might get a "clean" looking roof, but you have fundamentally compromised its structural integrity, effectively destroying it and instantly voiding any manufacturer warranty.
The only method approved by the Asphalt Roofing Manufacturers Association is Soft Washing. We apply a chemical mix using agricultural sprayers that produce zero pressure. The mix dissolves the algae, completely sterilizes the roof, and preserves 100% of your protective granules.