How to Float a Shower Pan Mortar-Mix Style

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A homeowner's guide for floating a shower floor with a mortar mix for a professional looking shower floor.

A good shower floor does not puddle or hold water. A shower pan determines the floor's slope to the drain and forms a base for the tile to bond to. If the pan has dips, the tile will allow puddles. A mortar-mix shower pan can be floated to fit any shower, regardless of shape or size. This and the total cost of labor and materials gives mortar-mix shower pans an advantage over pre-made fiberglass shower pans.

1) Clean and inspect the shower pan's base. Remove all of the dirt and debris. If the shower pan base has a rubberized membrane, inspect the membrane for rips or puncture wounds. Repair the membrane as needed with the proper sealant -- available at most home improvement stores. If the shower pan base is cut into a concrete slab, called a "recessed pan," then verify the shower walls extend below the top of the slab by 1/2 inch. Add or remove the shower walls as needed. Cover the shower drain with masking tape.

2)Prepare the shower pan's collar, the space between the base and the shower wall. If the shower pan uses a rubberized membrane, cut a strip of wire lathe and slip it between the shower wall and the membrane. Position the lathe so its bottom rests on the membrane; use care to avoid puncturing the membrane. If the shower has a recessed pan, then dampen the concrete with water. The mortar mix will bond better to damp concrete than it will to dry concrete.

3) Dump one 80-lb bag of portland cement into a pile on a large hard surface; a concrete floor works best for this step. Add 10 gallons of clean dry sand. Premix the portland cement and the sand with a flat shovel. Sliding the flat part of the shovel across the concrete floor, lifting the mixture up and then dumping it onto the center of the pile works best. Continue to mix until all of the portland cement has mixed with the sand.  

4) Pour 1 gallon of water into the mixture. Stir the water into the mixture with the shovel. The goal is to add just enough water to activate the portland. The mortar mix will turn a darker color when the water mixes with it. If you add to much water add more dry portland cement and sand.

5) Form a collar in the shower pan with the mortar mix. Dump one 5-gallon bucket of mortar mix into the shower pan's base. Use a 12-inch flat trowel to force the mortar mix into the collar. Completely fill the collar with the mortar mix.

6) Scrape the extra mortar mix from the collar with the flat trowel. Hold the long edge of the trowel against the drywall and shave the mortar. The goal is to have a flat surface that is flush with the shower wall.

7) Build a 2-inch wide bench around the perimeter of the shower floor with mortar mix. The bench's height will be determined by the floor's slope. Hold one end of a bubble level on the floor drain. Place the other end of the level on the farthest wall. Lift the wall end of the bubble level until there is a 1/4-inch per foot slope. Make a mark in the collar at this height. Form the bench at this height. Use a lot of pressure when forming the bench. Use the bubble level to keep the bench level and shave the extra mortar mix with the flat trowel.

8) Fill the area between the bench and the drain with mortar mix. Stamp the mortar with a wood block until the mix has compressed.

9) Float the shower floor. Hold one end of a straightedge on the bench and the other end on the drain. Use the straightedge to carve away all high spots. Use the material left over from shaving the float to fill in the low spots. Pack the loose material with the wood block. 

Clean up all left over material before it dries. Let the shower floor float dry for at least 2 hours before laying the shower floor tile. Most beginners should let the float dry completely before laying tile. Laying tile on a wet float requires a greater level of skill.

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