Tips for Building
Always order more tiles than the bare area. Allow 10 percent waste for a straight layout and 15 percent for a diagonal one, plus a spare box for future breakages: the same reference will not come from the same firing batch two years later.
For your tile format
cm tiles: a 6 to 8 mm trowel
Under 30 cm, a single bed with a 6 or 8 mm notched trowel is enough, and straight cuts go on a manual tile cutter.
For your tile format
cm tiles: a 10 mm trowel and levelling clips
Between 30 and 60 cm, move to a 10 mm trowel and use levelling clips: at that size, a tile standing two millimetres proud shows and catches.
For your tile format
cm tiles: back-buttering required
Beyond 60 cm, makers require adhesive on the floor and on the back of the tile. A levelling system becomes essential, and a wet saw, which you can hire, beats a manual cutter.
The assumptions behind this calculation
- Adhesive: 4 to 5 kg/m² for tiles under 30 cm, 5 to 7 kg/m² up to 60 cm, 8 to 10 kg/m² beyond that, where back-buttering is the rule. These are the orders of magnitude from datasheets; yours has the final say, since consumption depends on the trowel and on how flat the base is.
- Grout: the makers' formula, ((L+W) ÷ (L × W)) × joint width × tile thickness × 1.6, with tile dimensions in millimetres.
- Tiles: a tile's area is calculated including the joint, then your waste allowance is added. The calculation ignores the set-out: a narrow room with many cuts uses more.
- Spacers: one per tile as a minimum. With plain crosses, buy generously.
What this calculator does not replace
It gives quantities, not a method. The base, the primer, the adhesive class and, in a wet room, the tanking system depend on your job: the adhesive datasheet and, where needed, a professional decide. Over underfloor heating or on timber, the preparation is different.
Frequently asked questions
How much waste should I allow?
10 percent for a straight layout in a simple room, 15 percent for a diagonal one or a room full of cuts. Add a spare box: firing batches change, and the same reference found two years later will not match exactly.
Do I need to back-butter?
The adhesive maker says so on the datasheet: it is the rule beyond a certain format, outdoors and under load. The check on site stays the same: lift a freshly laid tile and see whether its back is covered.
How long before walking on the tiles and grouting?
The times are printed on the adhesive bag, often around 24 hours for a standard adhesive and a few hours for a rapid-set one. Grouting waits the same time.