This article reports on the repair of an approximately 100-year-old hydraulic structure with different strain-hardening retrofitting materials under special consideration of application technology, labour costs, material properties and durability. The lock structure was characterised in places by very poor concrete quality (compressive strength below 5 MPa) and wide separating cracks (crack width over 2 cm), while the load-bearing capacity did not cause any concern. The aim of the repair campaign was to restore the impermeability of the lock with the minimum possible changes in the cross-section of the existing structure. Depending on the section, the repair was carried out with strain-hardening cement-based composite (SHCC) or with textile reinforced concrete (TRC), whereby TRC was applied in four variants which included different types of grids and numbers of layers. Epoxy resin, SBR and mineral-impregnated carbon fibre yarns were used. None of the areas repaired was smaller than 35 m². The entire structure was monitored with regard to its deformation behaviour for half a year before the repair and regularly monitored after the retrofitting for up to two years. The observations showed that all applied retrofitting variants can effectively bridge the cracks despite the low layer thicknesses of max. 3 cm and that the permeability of the entire structure decreased considerably.