How to Tile Over a Rubber Membrane in a Shower

Mortar Bed Installation

• 1

  Secure the central base of the shower floor mud forming device over the shower drain with two screws driven through the existing mortar bed and into the plywood base as directed in the instructions. The central base contains an upward facing round vertical shaft to act as a fulcrum for the slightly upward angled pivoting arm used to smooth the surface of the mortar bed and create the necessary drainage slope.

• 2

  Slide the right-angle compound leveling device provided in the kit sideways onto the vertical shaft so the inside corners rest against the shaft. The leveling device has two horizontal spirit levels mounted on each opposing right-angle leg, and a second vertically oriented spirit level mounted on its outside corner. Hold the leveling device in place and rotate the knurled adjusting knob on the end of the base plate. Keep adjusting the knob either way and rotating the leveling device around the shaft until all three spirit level bubbles are centered in two directions.

• 3

  Mix four parts of sharp builder’s sand with one part of Portland cement in a large plastic mixing tray until the cement and sand are blended together to form an even grayish color. Add water sparingly and mix the mortar with paddle until it is evenly moist. Keep testing the mix by compressing a ball of damp mortar in your hand during the mixing process.

• 4

  Continue mixing and adding small amounts of water until your test ball of mortar keeps its shape and no moisture remains on your hand. If the ball is slightly sticky, then it’s too wet; if the ball crumbles and doesn’t hold its shape, it’s too dry.

• 5

  Shovel the prepared mortar mix evenly onto the shower floor until the surface is above the base plate, and pack the surface down lightly with the back of the shovel. Tamp the mortar firmly down around the base plate for later finishing.

• 6

  Wipe the base plate clean and slide the pivoting bar onto the vertical shaft on the base plate covering the drain cover. The pivoting bar consists of a 12-inch long, 3-inch wide and 1/4-inch thick metal bar welded at a slightly upward facing angle to a sturdy tube that acts as a hub designed to fit over the vertical shaft. A second 12-inch long mortar surface smoothing bar is bolted to the bar, and offset to protrude downward beneath the bar to produce a 1/2-inch downward facing step 6 inches away from the hub. The second bar and all extension bars provided are fitted with two rivet shaped sideways facing attachment lugs used to clamp various lengths of additional extension bars onto the end of the fixed smoothing bar.

• 7

  Lower the smoothing bar hub over the vertical shaft and slide it down until the stepped underside of the smoothing bar rests on the surface of the packed mortar. Work from the middle of the shower floor toward the left side wall. Pivot the bar gradually from side-to-side to clear excess mortar until you achieve a smooth, 90-degree upward sloping arc on the surface. Keep removing excess mortar with the edge of a small flat finishing trowel and continue smoothing the surface down until the bottom of the hub rests on the base plate. This will produce a slightly outward sloping surface at the desired thickness.

• 8

  Lift excess semi-dry mix from the surface as you work using the side and front edges of a flat 18-inch finishing trowel. Apply a finish as you work by troweling the surface smooth while following the slope. Use the front and side edges of the trowel to remove excess mortar.

• 9

  Keep finishing the surface with the trowel as you work the smoothing bar from side to side, and follow the slope evenly as you progress. If necessary, add selected longer and longer extension bars to the smoothing bar to reach the side walls of a wide oblong shower.

• 10

  Follow the slope and feather the ends of the mortar surface smoothly into the corners by removing excess mortar with the front edge of the trowel. If you notice any hollows, sprinkle a handful of semi-dry mortar into the depression, tamp down and trowel the surface smooth.

• 11

  Repeat the smoothing and leveling action on the right side of the shower enclosure. Once this is done, finish the narrow space between the back wall and the front curb by removing the extension bars and using the fixed short smoothing bar together with a small finishing trowel.

• 12

  Once the entire floor is finished with a smooth, slightly sloped surface, remove the smoothing bar and detach the mortar forming device base plate covering the shower drain. This will leave a 12-inch wide circle of unfinished mortar around the drain left by the step between the smoothing bar and the hub. Cover the holes in the drain cover with strips of to prevent loose mortar from clogging the drain.

• 13

  Feather the surface in from the outer edges of the unfinished section toward the drain by lifting off excess mortar with the trowel and smoothing the surface down to follow the slope inward. Ensure that the surface of the mortar around the rim of the drain is finished slightly below the rim to allow for the thickness of your tiles. Allow 24 hours for the mortar to set before proceeding with the tiling operation.

Tiling

• 14

  Start at the right back corner if you are tiling a small square enclosure. Alternatively, mark the center point of the back wall with a felt pen and mark a corresponding point at right angles to the center line on the shower curb. Use this as your datum line for the first row of tiles and work outward so any cut tiles will be placed along the side edges of the enclosure.

• 15

  Mix up a batch of powdered thin-set tiling mortar and water to the consistency of mashed potatoes in a plastic bucket. Lay the first row of thin set along the back edge of the enclosure with a 3/16- by 5/32-inch notched trowel. Draw the trowel across at about a 30-degree angle to the surface while scrape the teeth of the trowel on the mortar bed to maintain the proper thin set thickness. Ensure that the row of thin set is wide enough to accommodate 12-inch square sheets of small square mosaic tiles.

• 16

  Place the first sheet of tiles either in the top right corner, or on you pre-measured center datum line, whichever is applicable. Press the mosaic tiles down firmly with the flat of your hand, but don’t apply enough pressure to squeeze any thin-set mortar through the grout line gaps between the small mosaic tile squares.

• 17

  Continue laying the first row of tiles the same way. Ensure an even look by spacing the gaps between mosaic sheets wide enough to match the grout line gaps between the small mosaic squares on the sheet.

• 18

  Measure and mark a cut line on the outer row of tiles with a felt pen where applicable. Place the sheet of tiles on a firm surface. Position a steel rafter angle square against the mark. Score the cut line with a carbide-tipped tile-scoring tool two or three times, and then cut the tiles along the scored line with a pair of tile nipping pliers.

• 19

  Remove a small square of tiles from the applicable mosaic sheet when you reach the drain opening. Ensure that the opening clears the drain outlet cover by at least an inch on all sides. Continue applying thin-set mortar and laying the sheets of tiles as previously described over the rest of the floor.

• 20

  Mark and trim the individual mosaic squares removed earlier to fill the gap surrounding the drain cover. Use the edge of the tile nipping pliers to remove small chips at a time instead of trying to make single large cuts. Apply a thin layer of thin-set mortar to the back of the shaped tiles with a putty knife and press them into the gap while maintaining even spacing on the grout lines.

• 21

  Measure and mark the cut lines on the same tiles used to cover the walls of the shower enclosure. Ensure that the cut tile is wide enough to cover the three exposed faces of the shower enclosure curb. Place the tile in a tile cutting tool with the cut mark lined up with the carbide cutting wheel on the tile cutter handle. Grab the handle of the tile cutter fitted into the sliding bar across the tool. Tilt the handle toward the front and draw the cutting wheel firmly across the tile to score the surface. Move the cutting tool handle along the slide to the middle of the tile and push the handle forward to lever the front edge of the tool downward; this will snap the tile neatly in two.

• 22

  Apply a layer of thin-set mortar to the front face of the curb and press the tiles into place while maintaining an even grout line spacing to match the wall tiles. Repeat this procedure and apply cut tiles to the top and rear face of the curb. Note: The top of the curb must slope slightly toward the inside of the shower enclosure to allow for proper drainage.

• 23

  Allow the thin-set mortar to cure overnight before applying grout.

Applying grout

• 24

  Inspect the grout lines and scrape out any thin-set mortar that you managed to squeeze out between the tiles with the tip of a flat screwdriver.

• 25

  Wipe down the floor with a damp sponge to remove any dust clinging to the tiles.

• 26

  Mix up a batch of sanded grout with clean water, or if applicable, the recommended solvent to suit the particular brand of grout you’re using. Mix thoroughly for about five minutes to the consistency of builder’s mortar.

• 27

  Load a rubber tiling float with a fairly small amount of grout at a time to prevent it from drying out too soon. Hold the float at a 30- to 45-degree angle to the floor and float the grout into the grout lines by applying moderate downward pressure and moving the float diagonally across the grout lines from corner to corner. Repeat by filling the grout lines on the curb tiles.

• 28

  Allow 20 to 30 minutes drying time for the grout to set slightly without hardening. Wipe down the tiled surface gently with a clean damp sponge to remove excess grout. Rinse the sponge in a bucket of clean water and squeeze it out between every three or four strokes.

• 29

  Allow another 15 minutes drying time between sponging, and repeat the process three or four times until there is no longer any powdered grout clinging to the surface.

• 30

  Allow the grout to set overnight. Apply grout sealer to the grout lines carefully with a thin paint brush to complete the procedure.