Applying waterproofing membrane in a shower will prevent water from penetrating the tile grouting thus avoiding other impairments. In case that water manages to infiltrate the grouting of the tiles, the membrane acts as a protector and water will displace towards the drain, thus precluding mold from forming.
In previous years, plumbers used to waterproof showers with thin sheets of lead. However, since lead is potentially hazardous, a substitute was introduced, chlorinated polyethylene (CPE), which has since replaced lead. This provides a durable barrier against moisture.
Although installation is hectic, any DIY enthusiast is able to perform this task.
Step 1 - Examine the Shower
Before starting out any work, examine the shower area for any nails and other sharp products. Presuming you cannot remove the nails, you need to recess these or flush them down with a sander.
Clean the area using a vacuum cleaner to achieve a dust free and greaseless area.
Step 2 - Level the Floor and Walls
Apply a thin layer of mortar to the walls and shower area. Use a waterproof substrate specially manufactured for showers. When applying the substrate to the base, slope it down towards the drainpipe to avoid water settling.
Step 3 - Apply Membrane To The Shower Area
Calculate the shower area along its perimeter. In your calculations add up any upturns you might have. Having planned your calculation, roll out the membrane. Generally, the membrane is marked with lines at approximately six-inch intervals. However, consider these as a guideline and not as accurate measurements. Cut the membrane according to your calculations using a utility knife or scissors.
As for the corners of the shower base, manufacturers recommend the use of prefabricated ones. If these are not available, incise the corners with a single cut. The leftover will eventually overlap in the corner.
Place the membrane in the shower base and press firmly in all corners. Cut a hole for the drain.
Withdraw the membrane and apply adhesive to the membrane. Fix it to the shower area ensuring it bonds tightly to the floor taking special care for the corners and the drain.
Step 4 - Apply Membrane to the Walls
Follow the above steps, calculate the membrane, and attach the membrane to the walls. If the area that requires waterproofing is wider than the width of the membrane sheet, you will need to seam the sheets together.
Between each sheet, leave an overlap of approximately three inches. Use a hot-air gun flattening with a hand roller. Heat improves effectiveness of seaming. Use nails to fix the upper edge. Use copper nails and recess as required.
Step 5 - Test and Apply the Shower Pan
Once you have installed the waterproof membrane, clean the area thoroughly. Test the shower area for any leakage. Fill the shower floor with water, marking the upper edge with a marker. The next day check whether there was a decrease in water. If so, remove the water and apply another three-inch width of membrane over the seams.
Once satisfied, apply an adhesive as recommended by the membrane manufacturer to the floor and place the shower pan in place. Leave to dry overnight. Attach the drain the next day applying sealer on the edge.
Following all this, you will need to tile the area covered with membrane. You can do so with the peace of mind that no water will penetrate from your shower area.