Tiling a Niche in a Shower: Complete Professional Guide

This is the most critical step. Apply waterproofing membrane to the entire niche interior, including the sill, back wall, sides, and ceiling. Extend the membrane at least 2-3 inches beyond the niche opening onto the surrounding wall.

For liquid membranes, apply 2-3 coats according to manufacturer specifications. For sheet membranes, ensure all seams are properly sealed and corners are reinforced with additional material.

The trowel size must match your tile thickness for optimal thin-set coverage:

• 1/4" thick tiles: Use 1/4" x 1/4" square-notched trowel
• 3/8" thick tiles: Use 3/8" x 3/8" square-notched trowel
• Mosaic tiles: Use 3/16" V-notched trowel

Square notches create better adhesion for wall tiles. The ridges should stand up without sagging—if they droop, your thin-set is too wet.

The sill (bottom shelf) is the first tile you install. This critical piece requires special attention:

1. Apply thin-set to the niche sill area with your trowel
2. Back-butter the sill tile with additional thin-set
3. Press the tile firmly into place
4. Create a 1/16" forward slope toward the shower (critical for drainage!)
5. Extend the sill 1/16" beyond the niche opening if using trim
6. Use a torpedo level to verify the slope
7. Use a laser level to ensure it's level side-to-side

After the sill is set, move to the back wall:

1. Comb thin-set onto the back wall with your notched trowel
2. For mosaic sheets, embed by hand first, then press with grout float
3. For individual tiles, back-butter each piece before setting
4. Ensure factory edges face the outside for clean grout joints
5. Use tile spacers (1/16" or 1/8") to maintain consistent grout lines
6. Remove thin-set that oozes from joints with a utility knife and damp sponge

For mosaic tiles: You can cut sheets with a wet saw or tile cutter. Use 1/16" horseshoe shims to space pieces evenly when piecing together cut sheets.

Install the top tile before the side tiles:

1. Measure and cut the top tile to fit
2. Apply thin-set and back-butter the tile
3. Position with factory edge facing outward
4. Use your laser level to ensure it's level with the sill
5. If installing multiple niches, verify all top tiles align

This tile hides any imperfections in the back wall tiles and creates a clean finished look at the top of your niche.

The side tiles are the most challenging because they must accommodate the sill's slope:

1. Measure the front dimension between top and bottom tiles
2. Account for the sill's 1/16" slope when measuring
3. Make a scribe cut on the bottom edge to match the slope
4. Use an angle grinder with diamond blade for precise cuts
5. Test fit before applying thin-set
6. Apply thin-set and embed the side tiles
7. Use laser level to verify they're plumb (perfectly vertical)

Choose your preferred edge finishing method:

Wait 24-48 hours after tiling before grouting:

1. Remove all tile spacers
2. Clean out any remaining thin-set from joints
3. Mix grout according to manufacturer instructions
4. Consider using latex additive instead of water for better performance
5. Apply grout with grout float at 45° angle to joints
6. Work grout into joints completely, eliminating air pockets
7. Remove excess with float held at steep angle
8. Clean tiles with damp (not wet) sponge using circular motions
9. Rinse sponge frequently
10. Allow grout to cure per manufacturer specs (usually 72 hours)