Roof cleaning uses specialized low-pressure equipment and cleaning solutions designed specifically for roofing materials. Pressure washing uses high-pressure water that can damage shingles, strip granules, and force water under roofing materials where it doesn’t belong. The cleaning solutions in professional roof cleaning do the actual work of killing algae, moss, and lichen. The low pressure is just for application and rinsing. Pressure washing relies on water force alone, which means it has to be strong enough to potentially cause damage. Professional roof cleaning also includes proper safety equipment, insurance coverage, and knowledge of different roofing materials. A pressure washing approach might work for driveways and sidewalks, but roofs require specialized knowledge and equipment to clean safely and effectively.