Method of filling cavities, joins and gaps in a substrate, comprising the steps of: a) mixing the first component A and the second component B of a two-component polyurethane composition consisting of a first component A and a second component B; wherein - the first component A comprises - at least one polyol A1 having an OH functionality in the range from 1.5 to 4 and a mean molecular weight (number average) M n, measured by means of GPC against polystyrene, in the range from 250 to 15 000 g/mol, and - at least one diol A2 having two hydroxyl groups joined via a C2 to C9 carbon chain, and - at least one compound T having at least one thiol group; and - the second component B comprises - at least one polyisocyanate I; wherein one of the components additionally comprises at least one metal catalyst K for the reaction of hydroxyl groups and isocyanate groups that is able to form thio complexes; and wherein the molar ratio of all the thiol groups in the at least one compound T to all metal atoms in the at least one metal catalyst K is between 1:1 and 250:1; and wherein the molar ratio of all NCO groups in the polyisocyanates I to all OH groups in the polyols A1 and A2 = 0.9:1 - 1.2:1, especially 1.0:1 - 1.1:1; and wherein the polyurethane composition, directly after mixing of components A and B at 23°C, is free-flowing, preferably self-levelling, and has a viscosity, measured at 20°C on a plate-plate viscometer with plate separation 1 mm and plate diameter 25 mm, of < 5000 Pa·s at a shear rate of 0.01 s -1, and of < 500 Pa·s at a shear rate of 1 s -1, and of < 50 Pa·s at a shear rate of 10 s -1; b) pouring the mixed polyurethane composition into the cavity, join or gap to be filled in the substrate, c) curing the polyurethane composition in the cavity, join or gap. a) mixing the first component A and the second component B of a two-component polyurethane composition consisting of a first component A and a second component B; wherein - the first component A comprises - at least one polyol A1 having an OH functionality in the range from 1.5 to 4 and a mean molecular weight (number average) M n, measured by means of GPC against polystyrene, in the range from 250 to 15 000 g/mol, and - at least one diol A2 having two hydroxyl groups joined via a C2 to C9 carbon chain, and - at least one compound T having at least one thiol group; and - the second component B comprises - at least one polyisocyanate I; wherein one of the components additionally comprises at least one metal catalyst K for the reaction of hydroxyl groups and isocyanate groups that is able to form thio complexes; and wherein the molar ratio of all the thiol groups in the at least one compound T to all metal atoms in the at least one metal catalyst K is between 1:1 and 250:1; and wherein the molar ratio of all NCO groups in the polyisocyanates I to all OH groups in the polyols A1 and A2 = 0.9:1 - 1.2:1, especially 1.0:1 - 1.1:1; and wherein the polyurethane composition, directly after mixing of components A and B at 23°C, is free-flowing, preferably self-levelling, and has a viscosity, measured at 20°C on a plate-plate viscometer with plate separation 1 mm and plate diameter 25 mm, of < 5000 Pa·s at a shear rate of 0.01 s -1, and of < 500 Pa·s at a shear rate of 1 s -1, and of < 50 Pa·s at a shear rate of 10 s -1; - the first component A comprises - at least one polyol A1 having an OH functionality in the range from 1.5 to 4 and a mean molecular weight (number average) M n, measured by means of GPC against polystyrene, in the range from 250 to 15 000 g/mol, and - at least one diol A2 having two hydroxyl groups joined via a C2 to C9 carbon chain, and - at least one compound T having at least one thiol group; and - at least one polyol A1 having an OH functionality in the range from 1.5 to 4 and a mean molecular weight (number average) M n, measured by means of GPC against polystyrene, in the range from 250 to 15 000 g/mol, and - at least one diol A2 having two hydroxyl groups joined via a C2 to C9 carbon chain, and - at least one compound T having at least one thiol group; and - the second component B comprises - at least one polyisocyanate I; - at least one polyisocyanate I; wherein one of the components additionally comprises at least one metal catalyst K for the reaction of hydroxyl groups and isocyanate groups that is able to form thio complexes; and wherein the molar ratio of all the thiol groups in the at least one compound T to all metal atoms in the at least one metal catalyst K is between 1:1 and 250:1; and wherein the molar ratio of all NCO groups in the polyisocyanates I to all OH groups in the polyols A1 and A2 = 0.9:1 - 1.2:1, especially 1.0:1 - 1.1:1; and wherein the polyurethane composition, directly after mixing of components A and B at 23°C, is free-flowing, preferably self-levelling, and has a viscosity, measured at 20°C on a plate-plate viscometer with plate separation 1 mm and plate diameter 25 mm, of < 5000 Pa·s at a shear rate of 0.01 s -1, and of < 500 Pa·s at a shear rate of 1 s -1, and of < 50 Pa·s at a shear rate of 10 s -1; b) pouring the mixed polyurethane composition into the cavity, join or gap to be filled in the substrate, c) curing the polyurethane composition in the cavity, join or gap.