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Porcelain is dense and absorbs very little water; ceramic is softer and easier to cut. Both are fixed with cement-based tile adhesive and the joints are filled with grout. A tiled floor is rigid, so movement has to be taken up by joints at the walls and in large areas.
Layout comes first
Do not start against a wall. Snap reference lines so that cut tiles at opposite walls are about the same size and none is a thin sliver. The planner shows exactly which tiles are cut and to what size, so you can shift the start point before buying adhesive.
Key numbers
| Rule | Typical value |
|---|---|
| Grout joint | 2–3 mm for rectified tiles, 3–5 mm for others |
| Movement joint at walls | 5–6 mm, filled with silicone |
| Adhesive coverage | At least 80% in dry rooms, 95% in wet areas |
| Offset for long tiles | Max 33% when any side is longer than about 45 cm |
| Smallest cut | Avoid pieces narrower than a third to half a tile |
| Spare | 10%, 15% for diagonal or herringbone |
Installation in short
- Make the floor flat and prime it. Large tiles need a flatter floor than small ones.
- Snap layout lines from the planner's start point.
- Mix flexible C2 adhesive and comb it in one direction with a notched trowel sized for the tile.
- Back-butter large tiles with a thin layer, then press and slide them into place across the comb lines.
- Use spacers, and levelling clips for tiles 45 cm and longer.
- Lift a tile now and then to check coverage.
- After 24 hours, grout diagonally across the joints and sponge clean.
- Seal the wall joints with silicone, not grout.
Why the 33% rule? Long tiles have a slight bow from the kiln. With a half offset the high middle of one tile meets the low ends of the next, which shows as lippage. A third offset or less hides it.