This is how to frame and pour a concrete shower pan for use with or without tile. The most important thing is to make the shower pan leak proof.
We first need to frame in the shower pan with 2x10 lumber around the bottom of the floor and regular 2x4 studs up the walls. The drain can be anywhere on the pan as long as we slope the concrete for proper drainage. For this example, we'll use a drain that is in the center of the shower pan.
Once that is framed in we will put in the first part of the drain assembly and then line the floor with tar paper in preparation for the floor mortar.
Next, we'll put down metal lath on top of the tar paper to hold the mortar in place. The floor mortar will have a consistency of soft clay. It will be easy to spread so start around the sides and work toward the center making a gradual slope to the drain.
After the mortar dries we will put down a rubber membrane to make a good seal to prevent leaking. This is a special plumbing membrane available at most plumbing stores.
Be sure to cover the entire shower pan floor with the membrane. We can cut a hole for the drain hole. Cut out a circle of the rubber membrane to fit over the first layer at the drain and glue this in place for a better seal.
We can now put the second piece of the drain assembly in place with screws and then prepare for the next layer of mortar.
Now is a good time to put in the concrete backerboard walls. These will cover the framing. We will also need to put the third piece of the drain assembly in so we know how high to pour the mortar.
Next we can pour the final layer of mortar. A gentle slope is also needed from the sides of the pan to the drain in the center.
We need to keep in mind that the tile will protrude just a little above the drain so the water can drain freely.
We can then lay the tile in place and secure it with tile adhesive.
Once the tile has been set for a day or so we can apply the grout all around.
This cutaway pic shows the different layers to help us better understand how a concrete shower pan is made.