How to tile a floor or shower: backer, waterproofing and joints
Make sure the floor is stiff and flat, put down the backer or membrane your tile system calls for, waterproof every wet surface, dry-lay the layout to balance the cuts, then set, grout and leave soft movement joints.
Tile and grout are not waterproof: a shower needs a waterproofing layer under the tile. Ask the installer which backer, membrane, mortar and grout the job uses, as one system.
Worked example
Example: one 12 × 10 ft floor, 24 × 12 inch tile, a 1/8-inch joint, 10 tiles to a box and 10% extra.
This example gives 7 boxes of tile.
| Pieces | Along the length × along the width | Cut |
|---|---|---|
| 9 | 23.38 in × 12 in | straight |
| 5 | 24 in × 10.88 in | straight |
| 1 | 23.38 in × 10.88 in | straight |
- Surface 1: 45 full + 15 cut = 60 tile positions
- 60 × (1 + 10/100), rounded up = 66 tiles
- ceil(66 / 10) = 7 boxes
Other calculators for this job
Every step of a flooring project: measure, the list, what it costs and the quotes.
Measure every surface
Measure floors and walls separately, including returns, niches, curbs and thresholds, and keep each tile on its own list. Note drains, changes of plane and fixed cabinets. The small surfaces take the most cuts and trim, so draw them too. The tile calculator turns these measurements into boxes and shows where the cuts fall.
Check what the tile goes on
Tile needs a stiff, flat base: a floor that bounces or dips cracks tile and grout. Note the real subfloor or wall backing and its condition. The Schluter-DITRA Installation Handbook lists which subfloors its membrane suits and what each needs first; ask the installer which of those assemblies fits your floor and what preparation it takes.
Waterproof the wet areas before tiling
In a shower the floor, walls, seams, inside corners, drain and valve openings all need to join into one waterproof layer before any tile goes on. With a DITRA waterproofing assembly that means the handbook’s seam, perimeter and connection details, made with its own parts; laying the membrane alone does not seal the joints. Ask whether your town inspects the shower before it is covered.
Dry-lay the layout
Try the tile direction and starting point in the tile planner so the cut pieces at opposite walls come out about the same size and none is a thin sliver. Check the doorway, the drain and the first obstacle. List edge trims and transition strips with their lengths. Buy all the tile from one production lot, printed on the box, so the shade matches, and keep the spare boxes for repairs.
| Pieces | Along the length × along the width | Cut |
|---|---|---|
| 9 | 23.38 in × 12 in | straight |
| 5 | 24 in × 10.88 in | straight |
| 1 | 23.38 in × 10.88 in | straight |
Leave soft movement joints
Tile needs flexible joints where it meets walls, where a floor turns up a wall and across large areas. Schluter’s handbook and its movement-joint FAQ say DITRA does not remove the need for them. Fill those joints with flexible sealant, not grout: the grout lines between tiles, the gap at the edges and joints in the building each do a different job.
Set, grout and wait before use
Mix the mortar and grout with the water their bags give and use them within their working time. Grout once the mortar has set as its bag says, then wipe off the haze. Keep the shower dry until the grout and sealant have cured to their labels, and keep photos of the waterproofing before it was covered.