● A Yearly Wash: Your deck is exposed to the elements every single day, with rain included. That exposure is exactly why your deck needs to be washed once a year. Dirt and debris can build up on the deck and even with sweeping, it can get caught in between the boards. When rain or any other moisture gets stuck along the boards it could cause wood rot, mold, mildew, and other issues that can severely damage the wood or even make your family sick. A yearly washing removes the dirt, debris, mold, mildew, and more from the deck.