Lilly Miller Moss Out Moss Killer Concentrate is ideal for getting rid of moss growth on roofs, decks, steps, patios, walks, fence posts and foundations. Formulated to work best when applied just prior to the time when fall rains begin or in early spring, Moss Out provides maximum coverage of 500 sq ft per 27 oz bottle. This moss killer quickly and effectively destroys existing moss and can add months or years of service to any surfaces.