M-1 Deck & Roof Cleaner Concentrate is used to restore natural color to decks and roofs. Removes dirt, grease, grime, pollen, tree stains, pollution, mold, mildew, algae stains and weathering. Can be used with a pressure washer. Will not harm or discolor shingles. Makes 10 gallons. 1 gallon cut 9:1 cleans 2000 sq. ft.