One-component polyurethane foam that polymerizes with atmospheric moisture. It is easy to use and apply. The foam is self-expanding and increases approximately twice during polymerization. It has excellent adhesion to wood, cement, stones, metals, etc. The application surface can be wet but not covered with ice. It is possible for a 700ml bottle to give up to 40 liters of polymerized foam but this largely depends on the working conditions (temperature, atmospheric humidity, available space for expansion, etc.). Since the foam expands 2 to 2.5 times during polymerization, it should be left free space to expand. Polymerized foam is fire resistant and non-toxic.