Abstract: A prefabricated building cubicle has a portion of the floor recessed to receive an interior bathroom module, which is also prefabricated, and contains plumbing lines and complete fixtures. The building cubicle has plumbing and electrical lines on one wall adapted to connect to the interior module when installed in the floor recess.The bathroom module can be disconnected and rolled through an openable area in one wall of the cubicle, such as that created by removal of a pair of sliding balcony doors. A new module can then be installed, such as a kitchen module or another bathroom, facilitating upgrading or conversion of hotel rooms to a condominium.