1-component polyurethane adhesives contain moisture-reactive binders. These consist of an isocyanate-containing prepolymer (pre-product), which reacts with water from the air and from the subsoil to produce PU, releasing carbon dioxide (CO2). Since the adhesives contain isocyanate, they are subject to labeling. They can be used almost without restriction for bonding parquet floors. By releasing the CO2, the adhesives foam minimally and can therefore partially compensate for hollow spots.