How to Install a Shower Floor Mud Bed

If you're putting in a new shower and have the plumbing all roughed in, then the next step is installing the shower floor mud bed. The mud bed gives slope to the shower floor and makes the water drain down easily. There are several different methods of creating a shower mud bed, but one that requires fewer steps and a little more money uses the fabric liner. The fabric liner takes an additional step out of the process by eliminating another layer of concrete.

Things You'll Need

• Tape measure
• Roofing felt or plastic
• Hammer
• Roofing nails
• Concrete backerboard
• Level
• Galvanized Screws
• Pencil
• Straight edge
• Board
• Sand
• Portland Cement
• Work gloves
• Trowel
• Water
• Mud Pan
• Drain
• Thinset
• Fabric membrane

Instructions

1. Build the framework for your shower. Make sure that you put backerboard on the threshold. Some people like to put a wire cage on it and only put backerboard on the outside wall of the threshold. Others put it on top, inside and outside walls. You'll need this up before you begin the mud shower pan. Measure the distance from the center of the drain to the wall or threshold on each side. For each foot of distance, you'll need to use 1/4 inch for the slope. If your wall is 3 feet from the drain center, then make a mark up the side of the wall 3/4 inch. Use a level to make the mark across the wall. This slopes down to 0 in the center of the drain. Do this on all sides.

2. Lay down a layer of roofing paper or plastic to prevent the floor from absorbing the water from the concrete and drying too quickly. This compromises its strength. Overlap it 4 inches on the sides and ends. On top of the roofing paper, lay wire mesh. Nail this down ever 6 inches. Mix the mortar. It is 3 to 4 parts sand to 1 part of Portland cement. Make it dry enough to hold the shape of a ball without crumbling if you drop it.

3. Put a loose amount around the drain area and push down the drain into the concrete. You need to have good support for the flange. Smooth it out so that there's a thin layer around the drain flange. Build a border around the edge the height of the line that you drew earlier. Once both are complete, fill the area in between the drain and the walls. This gives you proper slope and drainage. Smooth it and take a level to the concrete to make sure the slope is there.

4. Allow the area to dry overnight. Once it's dry, hang the concrete backerboard for the walls. You'll need to do this before you finish the pan. Set the board directly on the concrete. Coat the concrete with thinset and lay the pre-cut section with the opening for the drain. Cover the floor with membrane, smoothing it into place. Many kits have a special fabric that goes around the drain. Apply more thinset and attach this.

5. Coat up the wall 6 inches and 6 inches from the edge on the floor with thinset. Put the top half on the wall and the bottom on the concrete. Use the inside corners provided with most kits to seal the difficult spots. You'll need to make sure all areas have the membrane sealed to them. Wrap it around the threshold. You may need to overlap it at spots. Allow it to dry overnight.

6. You are saving the step of laying another layer of concrete. The fabric bed doesn't require it. You now need to test it for leaks. Plug the drain and put in 1 or 2 inches of water. Let it set overnight. If the water level is the same and you see no leaks, you're ready to drain it, dry it and finish the job. If you find a leak, you may need to add more waterproof membrane.