How to Make an Outdoor Shower Base

Rotate the miter saw blade 45 degrees to the left and lock in place. Set a 2-by-6-inch plank on the saw table with its 6-inch surfaces vertical. Holding the plank firmly against the guide fence, trim off the the left end of the plank.

Measure and mark the plank's longest side to 44 inches. Rotate the saw blade to 45 degrees to the to the right of center and lock in place. Set the trimmed plank on the saw table with its 6-inch surfaces vertical. Holding the plank firmly against the guide fence, trim the other end of the plank. The end cuts are convergent, not parallel. Measure, mark and cut three more pieces with the same dimensions as the first. These pieces are used to construct the frame of the shower platform.

Assemble the frame on a flat surface, with mitered corners like a picture frame. Have an assistant to hold the first mitered corner together as you install a corner brace on the inside of the first corner of the frame. Place the L-shaped bracket in the middle of an inside corner of the frame. Use a drill and driving bit to attach the bracket to the frame with coated decking screws. Repeat to attach corner brackets to the remaining three inner corners of the frame.

Measure the distance across the center of the assembled frame. Set the miter saw to make 90-degree cuts. Measure, mark and cut a 2-inch-by-6-inch plank to this dimension. Test fit the trimmed plank by placing it in the center of the frame. The center support plank should fit snugly between the framing members without causing bowing of the lumber. If it is slightly too long, shave off one end, using the miter saw. If is is a little short, the difference will be amended by the joist hangers.

Measure and mark the centers of two opposite framing members. Slide a joist hanger onto each end of the center support plank. Place the plank and joist hangers inside the frame, aligning the center of the plank to the center lines marked on the frame. The supporting ledges in the joist hangers should be next to the flat work surface. Screw the joist hangers first to the frame, then to the center support plank. Each steel plate should be affixed to a plank with a minimum of four screws.

Measure, mark and trim the 5/4-inch decking planks. For a clean look, trim the planks to 40 inches. To create a slightly larger platform, the planks can be trimmed to 46 inches. The frame will adequately support a 3-inch overhang on each end. As you trim the planks, lay them on the frame perpendicular to the center brace about 1/4 inch apart.

Stop cutting when you have enough decking planks to cover the frame. Inspect the cut ends of the planks. Turn the decking boards so the concave side of the tree rings face the frame. Arrange the planks on the frame so they are parallel and about 1/4 inch apart. The long edges of the planks can extend up to 1 inch past the outer edge of the frame.

Place a yardstick on the decking boards. Scribe a pencil line on the boards to indicate screw positions. The screws should pass through the decking board, then enter the center of the framing members. While this step is not strictly necessary, accurately aligned screws lends a professional appearance to the finished project. Attach the decking boards to the frame with screws evenly spaced, no more than 2 inches apart.