Tile installation: Substrate, waterproofing & joints
Plan the layers under the tile, the border cuts and the joints before ordering a stack of boxes.
Tile quantity does not establish that the floor can support tile or that a shower is waterproof. Confirm the complete installation system before laying out the finish.
Record each surface and opening
Measure floors and walls separately, with returns, niches and thresholds written down. Note drains, changes of plane and fixed cabinets. Keep different tiles on separate lists. A drawing that shows only the room perimeter can miss the small surfaces that need the most cuts and trim.
Confirm the substrate and assembly
Record the actual subfloor or wall backing, its condition and the selected system. The Schluter-DITRA Installation Handbook distinguishes substrate assemblies and requires their conditions to be met. Ask the installer to identify the applicable assembly and any preparation; the area calculator cannot choose support or solve movement in the structure.
Plan waterproofing before tile
For a DITRA waterproofing assembly, follow the handbook’s seam, perimeter and connection details with its specified components. Do not assume that installing a membrane alone completes every junction. Shower walls, drains and penetrations need their own compatible system details and any required inspection before being covered.
Dry-plan the grid and trim
Try orientation and starting offsets in the tile planner. Compare border cuts at opposite walls and around the first obstacle. List edge profiles, transitions and their lengths. Keep tile size, lot and shade information with the box count, and discuss usable offcuts rather than assuming all cut pieces can be reused.
Leave the right joints
Schluter’s handbook and movement-joint FAQ explain that DITRA does not remove the need for movement joints. Have the installer mark those locations before setting. Keep grout joints, perimeter accommodation and structural joints distinct; they are not interchangeable gaps to fill from the same bag.
Set, grout and release for use
Use the selected mortar, grout and waterproofing instructions for mixing, working time and cure. Do not substitute a generic water ratio or next-day use promise. Keep a written check of substrate preparation and covered waterproofing work, then confirm when the room may be walked on, cleaned or exposed to water.
See the measurement become an order
Example only: a 12 × 10 ft surface, 24 × 12 inch tiles, a chosen 1/8-inch joint, 10 tiles per box and 10% extra.
This example gives 7 boxes of tile.
- Surface 1: 45 full + 15 cut = 60 tile positions
- 60 × (1 + 10/100), rounded up = 66 tiles
- ceil(66 / 10) = 7 boxes