Building a base for an outdoor shower depends on the materials you select to use, but to build a wooden base, construct a 26-inch square using 4-by-4-inch lumber, and cover it with 1-by-4-inch boards. Other options for the base include concrete, cement pavers or smooth gravel.
When using wood for the shower base, choose pressure-treated lumber or materials that are naturally water and rot resistant, such as redwood. Bases larger than 26 inches square require center supports that run perpendicular to the boards that form the deck.
For a concrete base, build a wooden form, and fill it with mixed concrete. Once the concrete cures, add smooth river rock using quick-set concrete or nonslip tile to give the shower a finished look. Other options include staining or painting the concrete base.
Form a base with cement pavers by building a foundation with compacted sand. Lay the pavers in place, top with additional sand and sweep the base to move the topping sand into the cracks.
For a gravel base, outline the perimeter with lumber or lawn edging. Remove the grass, and fill the edging with smooth river pebbles. Avoid crushed gravel that is too sharp for bare feet.
Before installing the base, decide if you need to install a drainage system. While natural drainage can handle the water in many areas, showers adjacent to the house without a drain sometimes cause flooding of the basement.