Abstract: A modular curb assembly of pre-cast pre-finished components forming a base for supporting sidewalls of a shower stall or other enclosure attached to a floor. The curb is made from a plurality of pre-cast pre-finished components of substantially uniform shaped cross section joined in end to end relationship to each other and attached to a floor in a predetermined contour around the perimeter of the enclosure. The components may be straight, curved or in the shape of angular corners and are cast in various configurations which provide a choice of different end angles so that the contour of the curb can be varied depending upon which different combination of component configurations are used in any particular curb design.