A high-solids, moisture-catalyzed, single-component polyurethane base coat. GAF Elastuff® 101 Base Roof Coating, when used along with GAF Elastuff® 103 Roof Coating, creates a roof coating system that provides an excellent balance of tensile strength, elongation, and hardness, along with excellent durability, dirt and mildew resistance, chemical resistance, weatherproofing, and high abrasion and impact resistance (formerly known as United Coatings™ Elastuff® 101 Base Roof Coating).