Room modules for buildings

A room cell for use in a modular construction of buildings and configured to be stacked upon and support other room cells, the room cell comprises a base plate and side walls enclosing a usable interior space, wherein load-bearing components of at least some side walls are formed by panels of cross-laminated timber, and wherein the room cell comprises a duct that runs from top to bottom of the room cell, wherein, within the duct, the duct is confined at a bottom of the duct by a duct floor or at a top of the duct by a duct ceiling, wherein the duct floor or the duct ceiling is horizontally disposed and extends between a side wall of the room cell and a peripheral wall of the duct, the duct floor or the duct ceiling comprising a step projecting upwards or downwards, respectively, into the duct, the step comprising of an upward segment and a sideward segment, wherein the duct floor or the duct ceiling extends to and terminates at the upward segment so that a free volume that is opened at a bottom or a top, respectively, is defined in a recess that is carved out from the duct by the step, and the duct is for accommodating cables and pipes passing through a region of the step from the top to the bottom of the duct.