A dry setting installation (1) for generating a substantially dry working space for carrying out work at an underwater structure. The dry setting installation (1) has two side-walls (2), a back wall (3) and a bottom (4) thus forming a cofferdam. The dry setting installation furthermore has, for each side-wall, a side edge sealing (20) provided on the side-wall (2) edge for providing a substantially sealing contact between the side-walls (2) and the underwater structure. The dry setting installation also has a distance variation system (30) for varying the distance between the side edge sealing system (20) of the two side-walls (2).