Pressure washing your exterior surfaces on a regular basis is recommended; however depending on the surface, the time between washing varies. For your deck, fence and concrete surfaces, washing should be done on an as-needed basis. However, a professional roof wash typically last three years, but it is best to have a roof washing expert, such as Space Clean, check yearly for dangerous regrowth. As for your siding, although some people may need to have the exterior of their homes cleaned every few months, Space Clean recommends having your home soft washed yearly.