Abstract: A room element for a full-scale or small-scale building has a rigid frame or chassis consisting of a floor panel, composed of prefabricated panel sections rigidly connected in an end-to-end assembly by structural means, and prefabricated vertical load-bearing structures, rigidly connected to the panel adjacent the ends thereof, for supporting superimposed parts (e.g. the roof or ceiling, or a superimposed room element). At least one of the load-supporting structures may be integral with a panel section. The panel sections form the bases of the corresponding regions of the room element and at least one of them is incorporated in a three-dimensional prefabricated room element section, of unit form, which unit comprises such vertical load-bearing or non-load-bearing bearing structures substantially all the installations, required in that part of the completed room element. The unit may be a bathroom unit, staircase unit, heating unit, elevator shaft unit, or kitchen unit.