Over time, outdoor surfaces collect layers of dirt, mold, mildew, and grime that ruin your home's curb appeal and create slick, hazardous walkways. Power washing is typically needed once a year, especially in the spring or summer, to clear away the harsh buildup left behind by winter weather. It is highly necessary if you notice dark discoloration on your driveway or patio, green algae growing on your siding or decks, or if you are planning to seal your concrete or restain a wooden deck and need a perfectly clean slate.