The timing for soft washing your roof can vary depending on environmental conditions. Heavily shaded areas and areas with tree coverage could need cleaning as often as every 2-3 years; other areas may only need cleaned every 4-6 years or if black streaks begin to form on the roof. The black streaks are what is know as Gloeocapsa Magma, which feeds off the limestone granules in your shingles, breaking them down and shortening their lifespan.