To install a walk-in shower in a basement, find the drain used when the builder poured the concrete floor. Once located, use it to run drainage for the shower. Purchase or design a walk-in shower unit that is easy to access. Open up the floor where you want to place the shower, and then install the necessary plumbing. Add framing, install the paneling or shower stall insert, and then attach the faucets and shower head.
When opening the basement floor, remove any reinforcement materials, such as rebar or mesh that fall directly under the shower drain. Install the trap in that space. Use your outside vent stack to ventilate the shower drain, or install an auto-vent for proper drainage to avoid overflow and water damage.
Fiberglass shower panels require specific framing, and manufacturers include specifications for each type. Build the plumbing for the water flow into an interior wall with an access panel on the opposite wall. This facilitates any future repairs or construction. Once the shower walls are in place, test the plumbing for leaks to avoid water damage. After installing the faucet and shower head, install the door or curtain to keep water over the opening of the walk-in shower to avoid damaging the outer walls.