It’s tempting, but usually not recommended, especially for shingle roofs. High-pressure washing can strip protective granules from shingles, force water under them, and even damage flashing or seals. On tiled or metal roofs, careless pressure washing can still push water into joints and cause leaks.
If your roof looks dirty or has algae and moss, gentler methods are better. There are cleaning solutions designed specifically for roofs that can be applied and rinsed at low pressure. Sometimes, soft brushing combined with these products is enough.
If you feel the roof desperately needs a deep clean, it’s safer to call a professional who knows how to handle your roof type. They’ll use the right pressure and techniques. Saving a little time with a DIY pressure washer isn’t worth the risk of shortening your roof’s life or causing leaks.