Cracks in the building substance are structurally weak points. Penetrating water may cause damage and may reduce the usage and lifetime of the building. An elastic sealing or structural-bonding of the crack is required. In order to achieve this, the crack is filled over its entire course with a polyurethane injection resin via pressure injection. The injection resins which are applied can also be used in drinking water environments. By injecting into the damaged or cracked structures, secures and seals leaks, repair compromised structures and make them watertight again for the long term.