Krud Kutter Exterior Siding Cleaner gallon. The ultimate exterior siding cleaner, this proprietary formulation of Krud Kutter Exterior Siding Cleaner contains Sporex, a unique additive which removes tough stains from mildew, mold, algae, fungus and moss, and leaves the surface completely clean. In addition, special surfactants penetrate the surface to safely and easily dissolve the toughest stains from dirt, oil, grease, bird droppings, tree sap, and acid rain. It even removes gray weathering on wood, chalking, and oxidation. This product is safe, fast and effective and recommended for exterior siding (wood, vinyl, aluminum), roofing, gutters, wood fences and decks, stucco, brick and cement block, masonry, concrete driveways, walkways and walls, even RVs, patio furniture, and boats. One gallon covers 4,000 sq.ft.