This 32 oz. super concentrate with built-in hose sprayer covers up to 600 sq. ft. The revolutionary no-rinse cleaner that removes green and black algae, mildew, fungus and lichen stains from roofs, siding, decks, brick, stucco, and other exterior surfaces. It is biodegradable, noncorrosive, and does not require damaging power washing and/or brushing techniques, in fact no rinsing is required. Spray & Forget does not contain any bleach, chlorine, lye, heavy metals, or acids. The hose mount allows you to spray 20' from your ladder so going up on your roof might not be necessary. Simply spray it and forget it.