A prefabricated, polyurethane reaction injection molded, leak-proof shower module suitable for use in constructing a tiled shower includes a floor and a plurality of sidewalls wherein a first sidewall is taller than at least a portion of a second sidewall and the difference in height between the first sidewall and the second sidewall is sufficient to permit the attachment of a modular curb to the second sidewall. The floor is bounded along peripheral edges by the plurality of sidewalls which extend substantially vertically from the edges. A method of installing a tiled shower is implemented in one embodiment by applying adhesive material on a subfloor within an area bounded by stud framing, setting the prefabricated shower module in place on the subfloor, installing a prefabricated modular curb proximate to at least one sidewall of the module, attaching wallboard to the framing, and installing tile over the wallboard, module and curb.