How to Waterproof, Tile and Grout a Shower Floor

A properly built shower floor should do three things:

1. Keep water out of the structure

2. Drain cleanly without pooling

3. Hold up to years of daily use

If you’re remodeling a bathroom or building a shower from scratch, the floor is the part you want to get right the first time. This blog walks through the full process from waterproofing to finished tile, using generic materials and methods that apply to most modern surface-waterproofed shower systems.

Overview of the Process

The general sequence looks like this:

1. Install the inside corners

2. Install the main waterproofing sheet on the floor

3. Add outside corners and wrap the curb

4. Flood test the pan to confirm it’s watertight

5. Fit the drain trim

6. Dry-lay the tile

7. Set the tile in mortar

8. Grout the floor

9. Remove haze and get the surface ready for wall tile

Each step builds on the last. When you follow this order, the shower floor ends up clean, durable and fully protected.

Tools and Materials You’ll Need

You won’t need anything unusual. Here’s the basic list:

Waterproofing

• Waterproofing sheet membrane

• Preformed inside corners

• Preformed outside corners

• Thinset mortar rated for membrane installation

Tile and Drain

• Shower floor tile (mosaic, pebble, square, hex or any small-format tile)

• Extra tile sheets to pull individual pieces from

• Drain trim assembly with height and lateral adjustment components

Grout

• Cement-based grout

• Clean, cool water

Tools

• Utility knife with sharp blades

• Scissors

• Square-notch trowels

• Flat trowel or drywall knife for embedding membrane

• Margin trowel

• Bucket and drill with mixing paddle

• Soft grout float

• Sponges (wrung out almost dry)

• Microfiber cloth

• Painter’s tape

• Shop vacuum

Step 1: Install the Inside Corners

Inside corners are the most leak-prone parts of any shower floor, so start here.

1. Mix your thinset to a smooth, creamy consistency.

2. Spread thinset up the walls and across the floor where each corner will go.

3. Set each corner piece in the thinset.

4. Smooth it firmly with your drywall knife to remove air pockets and ensure full contact.

If your curb height is lower than standard, trim the upper edge of the corner pieces with scissors so they sit flush.

Step 2: Install the Main Waterproofing Sheet

In most small showers, you can line the entire floor and turn the membrane up the walls in one piece. Fewer seams mean fewer opportunities for leaks.

1. Pre-cut the sheet so it covers the whole floor and rises a few inches onto the walls.

2. Notch the corners so the sheet folds neatly without bunching.

3. Spread thinset over the entire floor using a square-notch trowel.

4. Set the membrane in place.

5. Embed it carefully with a flat trowel:

   • Work from the center outward

   • Remove air bubbles

   • Avoid pushing too hard into sharp corners

Around the drain, bring the membrane down only to the bevel where the drain opening will be cut later.

Step 3: Install Outside Corners and Wrap the Curb

Outside corners protect edges where water can escape if the membrane isn’t reinforced.

• Embed each outside corner in thinset with at least a couple inches of overlap.

• Wrap the curb completely unless part of it will sit behind fixed glass and never see water.

• You can flip inside corner pieces if you need a custom outside configuration, as long as the overlaps remain watertight.

Once these corners are in place, your waterproofing layer is continuous.

Step 4: Flood Test the Shower Pan

A flood test is the only way to confirm the pan is actually watertight.

Allow the Membrane to Cure

Let the thinset under the membrane cure for a full day so the membrane doesn’t shift.

Plug the Drain and Fill the Pan

1. Seal the drain with a test plug or other approved method.

2. Fill the pan with water up to the top of the curb.

3. Mark the water line.

4. Leave it for 24 hours.

If the water level is unchanged the next day, the pan is sealed.

Cut Out the Drain Opening

Use a hook blade to:

1. Make a small hole in the center to let the water drain.

2. Once visible, cut neatly around the bevel of the drain flange.

Now the pan is ready for tile.

Step 5: Fit the Drain Trim Assembly

Most modern shower drains come with:

• A height adjustment collar

• A lateral adjustment ring

• A grate that snaps into the collar

The collar lets you set the grate height to match your tile.The lateral ring lets you fine-tune the center so the grate lines up with your pattern.

Pre-assemble these pieces so they’re ready once the tile is set around them.

Step 6: Dry-Lay the Tile

Dry-laying helps you avoid awkward cuts and uneven seams.

1. Place a full sheet of tile over the drain location.

2. Remove the center pieces so the drain fits through.

3. Lay surrounding sheets and rotate each one to find the cleanest seam with its neighbor.

4. Pull off any tiles that interfere with the wall.

5. Save those loose pieces for filling in gaps later.

6. Mark your layout so you can put the sheets back exactly where they go.

If you’re using pebble or irregular mosaic, this step is especially important. A few minutes here saves an hour of frustration later.

Step 7: Set the Tile in Thinset

Choose the Right Trowel

Small tile sheets usually set well with a small-notch trowel, but it’s smart to test it.

1. Spread thinset with a small-notch trowel.

2. Press in one sheet.

3. Lift it to check coverage.

If you don’t see near-full coverage, switch to a larger notch. Good coverage is essential on small mosaic or pebble tile.

Set the Drain

When setting tile around the drain:

1. Pack thinset under the four corners of the drain trim so it’s supported.

2. Add thinset around the drain opening.

3. Leave the assembly slightly high; you’ll press it down into place once tile surrounds it.

Set the Tile Sheets

1. Spread thinset over the floor.

2. Before placing sheets, scrape excess thinset away from the walls so it doesn’t squeeze up.

3. Set each sheet according to your layout marks.

4. Fill perimeter gaps with loose pieces.

5. Use a grout float to gently tamp the tile so the tops form a consistent plane.

Allow the tile to cure overnight.

Step 8: Prepare Joints for Grout

Before grouting:

• Use a utility knife to remove any thinset that squeezed up between the tiles.

• Pay special attention near the drain.

• Vacuum the floor to remove debris.

Clean joints make for stronger, cleaner grout lines.

Step 9: Mix and Apply Grout

Most cement grouts mix easily, but follow the instructions closely.

1. Measure your water accurately.

2. Add grout to water, not the other way around.

3. Mix with a drill on low speed briefly, then let it rest (slake).

4. Remix lightly by hand.

Apply the grout:

1. Start at the back of the shower.

2. Work toward the entry.

3. Spread grout diagonally across the joints using a soft float.

4. Pack it firmly into deeper spaces, especially around the drain and walls.

Let the grout firm up until a light fingerprint barely marks it.

Step 10: Clean the Tile Surface

Use a nearly dry sponge to wipe excess grout:

• Rinse the sponge often, but wring it almost fully dry.

• Wipe diagonally to avoid digging into joints.

• Stop once the surface looks consistent.

Avoid over-watering. Too much water weakens grout and can wash out color.

The next day:

• Buff the tile with a microfiber cloth.

• This removes the last of the haze without re-wetting the grout.

Step 11: Final Check

At this point, your shower floor should look uniform, feel solid underfoot, and be fully waterproofed beneath the tile. You’re now ready to install wall tile, set the fixtures and finish the space.