If you’re trying to clean and freshen up your roof, avoid using a pressure washer. The pressure of the water is too hard on your roof’s shingles and could cause the shingles to crack and/or snap off. As an alternative to using a pressure washer to clean your roof, you can take a bleach and water solution and pour it onto your roof. After letting the solution sit for 20 minutes, you can rinse it off with clean water.