Making a concrete slab for an outside shower is easy for a person experienced in the concrete trade. Knowledge of elevations, forms, and finishing methods are needed to ensure a successful result. This project can be attempted by a homeowner if he or she is aware of all the steps involved.
Using a shovel, remove 8” of dirt in the area for the concrete slab for an outside shower. Establish elevation by first setting stakes at the proper dimension and making sure the stakes are square. To check square, pull a tape measure diagonally from corner stake to corner stake. Each distance must be the same. Using a level, mark the correct elevation on the stakes with a pencil. Tie a string line to the stakes at the pencil marks.
Using either steel concrete forms or forms made from 2’x4’ lumber, set the forms to the height of the string line. Add enough #57 gravel to bring the subgrade up to the proper elevation. Place a 4” to 6” drain in the center of the concrete slab for an outside shower. Pull a string line across the top of the form work and set the drain ½” below the string. The drain can be piped out under the form work into a dry-well or an existing downspout drain.
Four inches is the recommended thickness of a concrete slab for an outside shower. The amount of concrete needed can be figured by multiplying the length by the width and then dividing that number by 81. Place a piece of 10 gauge wire mesh for reinforcement in the form work, cutting out a hole to allow the drain to come through.
Place the concrete into the form work by using a 2’x4’ lumber as a straight edge. Set one end of the straight edge on top of the drain and set the opposite end on top of the form work. Pull the straight edge all the way around making sure one end of the straight edge stays on top of the drain and the other end stays on top of the forms until the entire formed up area is completed. Depending on the temperature, allow the concrete to have some set time before starting to finish the concrete slab for an outside shower. Finishing is done by using a steel trowel, magnesium hand float, and an edging tool set to a ½” radius. Sealer can be applied after the concrete slab for an outside shower is finished only if the floor is not to be tiled.