Tricks to Floating a Shower Pan

Required Layers

• Properly constructed tile shower pans consist of carefully floated mortar beds, as well as layers of other types of materials that work in combination, to ensure that the shower pan will be long-lasting and high quality. The bottom of the pan is the wooden sub-floor. Building paper is stapled to this floor and covered with a mortar layer to form the pre-pan. Waterproof CPE (Chlorinated Poly Ethylene) membrane is then placed on top of the mortar. Another mortar layer, metal lath and a final layer of mortar are added and floated before the tiles are laid.

Pre-Pan Mortaring

• The first layer of mortar added to the shower space creates the pre-pan and is installed on top of metal lath. Use thinset mortar with a latex additive to improve strength and mix it to a fairly dry consistency. Use a trowel to pack mortar into the lath and build up the pre-pan from the drain piece to the marked height line on the wall, creating the slope. Once the pre-pan has been largely filled in, check the slope with a level and make any adjustments, filling in low spots with mortar as needed. Finish the surface by running a wood float over it until the mortar is even and smooth.

Upper Mortar Layers

• The final mortar layers are applied in a manner similar to the pre-pan mortar and together with the metal lath create a bed about 1-1/2 inches thick. Apply mortar about half of this total planned thickness, cover it with metal lath with a hole cut for the drain then add mortar until the height marked on the wall is reached. Again, use a wood float to smooth the surface and make sure it slopes evenly to the drain.

Dealing With the Drain

• Drains for tile showers are different than standard fixture drains. These drains typically consist of three pieces and must be installed properly to ensure adequate drainage. The bottom piece of the drain should be glued to the drainpipe with PVC cement after the building paper is stapled to the subfloor. At this point, partially screw the bolts in and stuff a rag into the pipe to prevent mortar from falling into the pipe. After the metal lath, mortar and waterproof membrane are placed, locate and mark where the drain bolts are. Press down on the membrane and cut slits just large enough for the bolts to emerge. Carefully cut the membrane in the center of the drain to expose the drain and allow the middle drain piece to fit. Remove the bolts and place the middle drain piece then re-install the bolts and tighten them to create a watertight seal. Place the drain strainer piece before the final mortar layer and tiles are laid.

Sloping the Pan

• The proper slope for the shower pan must be established when placing and floating mortar for the pre-pan and maintained throughout subsequent layers. After the bottom drain piece is installed, mark the height of the bottom drain piece on the wall farthest from the drain. Measure the distance between this point and the drain center. For every 12 inches of distance, the pan bottom should rise 1/4-inch. Mark this new level on the wall and use a level to create a reference line on the walls around the pan. The mortar for the pre-pan should reflect this slope.