Tile adhesive and grout coverage
Adhesive and grout are often bought by eye, then topped up on the day or spare bags go back to the shop. They can be worked out in advance quite accurately. Below are the formulas mortar manufacturers use and an example for an ordinary bathroom.
Grout
Grout consumption depends on the volume of the joints to fill:
L and W are the tile length and width in mm, T the tile thickness in mm, J the joint width in mm, and 1.6 the density of cement grout in kg/dm³. Epoxy grout has a different density; take it from the product sheet. Add about 10 % for losses.
| Tile | Thickness | Joint | Coverage |
|---|---|---|---|
| 1200×600 | 9 mm | 2 mm | 0.07 kg/m² |
| 600×600 | 9 mm | 2 mm | 0.10 kg/m² |
| 600×300 | 9 mm | 2 mm | 0.14 kg/m² |
| 300×300 | 8 mm | 3 mm | 0.26 kg/m² |
| Mosaic 25×25 | 4 mm | 2 mm | 1.02 kg/m² |
Mosaic takes ten times more grout than a large format. That is the main source of mistakes.
Tile adhesive
Adhesive consumption depends on the bed thickness after the tile is pressed in. The bed depends on the tile size: the bigger the tile, the larger the trowel notch. Cement adhesive needs about 1.4 kg per m² for every millimetre of bed.
| Tile size, √(L × W) | Bed | On a wall |
|---|---|---|
| up to 100 mm (mosaic) | 1.2 mm | 1.7 kg/m² |
| up to 200 mm | 1.8 mm | 2.5 kg/m² |
| up to 300 mm | 2.4 mm | 3.4 kg/m² |
| up to 450 mm (e.g. 600×300) | 3.0 mm | 4.2 kg/m² |
| up to 650 mm (e.g. 600×600) | 3.3 mm | 4.6 kg/m² |
| up to 1200 mm | 3.7 mm | 5.2 kg/m² |
| over 1200 mm | 4.3 mm | 6.0 kg/m² |
Adjustments:
- Floors: about 0.3 mm more bed, as floors need full contact without voids.
- Tiles with a side of 800 mm or more are back-buttered, adhesive on both the substrate and the tile: about 0.7 mm more.
- Uneven substrate. Every extra millimetre levelled with adhesive adds 1.4 kg/m².
- Losses in the bucket and on the trowel: about 10 %.
The exact consumption of a given adhesive is on its technical data sheet; the table is for a first estimate.
Example: 25 m² of walls and 3.4 m² of floor
- Walls, 600×300 tile, 9 mm thick, 2 mm joint: adhesive 25 × 4.2 = 105 kg, grout 25 × 0.144 = 3.6 kg.
- Floor, 600×600 tile, 9 mm thick, 2 mm joint: bed 3.3 + 0.3 = 3.6 mm, adhesive 3.4 × 5.0 = 17 kg, grout 3.4 × 0.096 = 0.3 kg.
- Adhesive with 10 % spare: (105 + 17) × 1.1 = 134 kg, that is 6 bags of 25 kg.
- Grout with 10 % spare: (3.6 + 0.3) × 1.1 = 4.3 kg, that is 3 packs of 2 kg or one of 5 kg.
Don’t forget
- Primer: about 0.15 kg/m², two coats on absorbent substrates (plaster, plasterboard).
- Waterproofing: about 1.5 kg/m² per coat: the whole floor of a wet room, walls up to 200 mm, the shower zone up to 2 m.
- Screed for falls in a level-access shower is counted from the average screed thickness.
Work it out for your own room
ATELIER 3D lays out tiles from your measurements, counts tiles in boxes and adhesive and grout in bags, and shows the bathroom in 3D. 7-day trial, no card.
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