How to Waterproof a Glass Block Shower Wall and Base Installation

Scatter a few colored blocks through your shower wall to increase privacy.

Naturally water-resistant glass block is quite a versatile building material. Its translucent quality lets light filter through while the wavy texture helps preserve some privacy. Special shower pans are designed for glass block showers. Some of them are curved along one side to support a curved glass wall, which helps contain shower spray without a curtain or door. Waterproofing the adjoining wall and floor before installing the shower will protect your home and help add years of enjoyment.

Things You'll Need

• 4-ml plastic shower membrane or sheeting
• Scissors or utility knife
• Silicone sealant
• Stapler or pneumatic staple gun
• 3-inch galvanized screws
• Power drill
• Phillip's head screwdriver bit
• Cementitious backer board
• Alkali-resistant mesh drywall tape
• Thinset mortar
• Bucket
• Mud knife

Instructions

1. Spread out an end of the membrane over the bare shower floor. Adjust it to extend up the walls at least 8 inches. Cut off the excess membrane with scissors or a utility knife.

2. Press down on the membrane to locate the drain opening. Cut out the opening in a slightly smaller diameter than the drain pipe. Apply a thin bead of silicone on the floor around the drain pipe opening and press down on the membrane.

3. Smooth the membrane over the floor and up the wall. Staple the upper edge of the membrane to the wall studs.

4. Measure around the wall stud portion of the shower enclosure. Cut a piece of membrane to that length. Test-fit the membrane by holding it against a wall stud and adjusting it up or down. Let the bottom edge overlap the upper edge of the floor membrane by several inches. Staple the membrane to the wall studs around the enclosure at that height.

5. Cut another matching length of membrane and attach it to the wall studs above the first sheet, using the same overlap. Continue until you reach the top of the enclosure. Add more staples to fasten the membranes to the studs throughout the enclosure.

6. Cover every staple with silicone, if desired, as an extra measure of security.

7. Screw cement backer board sheets to the studs over the membrane using galvanized wood screws and a power drill with a Phillip's head bit.

8. Press fiberglass mesh tape against the backer boards, covering every seam.

9. Mix thinset mortar in a bucket according to the manufacturer's instructions. Scoop up the material on the edge of a mud knife. Spread a thin layer over every strip of tape and screw hole.

10. Seal every gap, seam and space with silicone.

Tips & Warnings

• If the wall studs are not exposed, remove old drywall or backer board before installing the waterproof membrane.

• Add insulation between the wall studs, if none exists, before installing the membrane.

• After installing the shower pan and the glass blocks, seal the seams with silicone instead of ordinary caulk, or use a sealing product that the glass block manufacturer recommends.

• Most glass block showers feature at least one wall that is not glass. If your enclosure will be free-standing and completely formed of glass, there is no need to waterproof anything except the floor under the shower pan. Glass block installation materials are inherently waterproof or water resistant.

• Mortar bed shower pans also need a waterproof membrane underneath.

• Thicker plastic membrane is acceptable, but do not use anything thinner than 4 ml.

References

• The Floor Elf; Installing Cement Backer Board for Tile in a Shower; Roger; April 2009

Resources

• This Old House; Give Your Shower and Tub Their Own Spaces; Leslie Plummer Clagett; January 2010