A standard one-piece shower and tub combination unit is purchased with rough-in dimensions of 60 inches wide, 31 inches deep and 73 3/4 inches high before installation. After the unit is installed, the finished unit is still 60 inches wide, but the measurable depth is 29 3/4 inches deep and the overall visible height is 72 1/2 inches.
A one-piece shower and tub unit is typically made of fiberglass or acrylic that is prefabricated as one solid piece, usually with built-in shelves. Advantages of this kind of fixture include ease of installation, affordable cost and relatively carefree maintenance. In addition to the standard unit, there are models available to fit varying needs, such as a taller unit with a finished height of 79 3/4 inches or a wider one with a finished depth of as much as 36 inches.