Abstract: A manhole or a catch basin is built up by stacking a number of pre-cast concrete units. The joints between the units are provided, prior to stacking, with a bead of a non-hardening, semi-liquid, mastic waterproof layer to enable subsequent removal of the units without damaging same. The pre-cast concrete unit of this invention is typical by having cutouts in the side wall and corresponding protrusions extending from one face thereof. Hand or tool receiving depressions are provided in one surface of the unit to facilitate the handling of the unit when increasing or reducing the overall height of a manhole. The shape of the unit not only facilitates the production of same but also assists in convenient handling. Due to generally smooth faces, the steaming-off of the waterproof layer prior to the storage of a removed unit is also facilitated.