Project guide
Tiling a floor: how many tiles, and how much adhesive and grout?
Measure the floor, add an allowance for cuts, then work out adhesive and grout from the tile size.
The short answer
Tiles = floor area x 1.1 (x 1.15 for a diagonal layout). Floor adhesive on a solid bed covers about 0.4 m² per kg (BAL), so a 3 x 2.5m floor needs about 21kg: 2 x 20kg bags. In 600 x 600mm tiles with 3mm joints it needs about 1.3kg of grout.
The formula
- Tiles (m²) = length x width x 1.1 (1.15 diagonal)
- Adhesive (kg) = area / 0.4 x 1.1, in 20kg bags
- Grout (kg) = area x (2 x tile size) / (tile size²) x 3mm x 10mm x 1.6 x 1.1, in 5kg bags
Worked example
A 3 x 2.5m kitchen floor (7.5 m²) in 600 x 600mm tiles, laid straight:
- Tiles: 7.5 x 1.1 = 8.25 m², so buy 9 m² (about 23 tiles)
- Adhesive: 7.5 / 0.4 x 1.1 = 20.6kg, so 2 x 20kg bags
- Grout: about 1.3kg, so 1 x 5kg bag
Materials checklist
- Floor tilesBought by the box: divide the m² by the coverage on the box and round up.
- Flexible tile adhesiveA flexible cement-based adhesive, 20kg bags, spread with a 10-12mm notched trowel.
- GroutCement-based floor grout, 5kg bags.
You'll also need
- Primer for the floor, and a backer board or uncoupling mat on timber floors
- 3mm spacers or a levelling clip system
- Notched trowel, grout float, sponge, tile cutter, spirit level, knee pads
Step by step
- Check the floorIt must be flat, clean and rigid. Board or overlay a timber floor that flexes.
- Set outFind the centre of the room and dry-lay a row each way so cut tiles at the edges are not too thin.
- Prime and spreadPrime the floor, then spread adhesive a square metre at a time and comb it with the notched trowel.
- LayPress and twist each tile, back-butter large tiles, and use spacers. Check level as you go.
- GroutAfter at least 24 hours, grout the joints, clean off with a damp sponge, then polish off the haze.
Tips from the manufacturers
- BAL gives about 0.4 m² per kg for floor tiles on a solid bed; thin wall tiles need less adhesive.
- Buy all the tiles from the same batch: shades can differ between batches.
- Keep a few spare tiles for future repairs.
Mistakes to avoid
- Tiling onto a floor that flexes, so the grout and tiles crack.
- Dabbing adhesive in spots instead of a full bed: hollow tiles break.
- Grouting too early, before the adhesive has set.
Frequently asked questions
How much extra tile should I buy?
About 10% for a straight layout and 15% for a diagonal or herringbone layout.
How much adhesive per m² for floor tiles?
About 2.5kg per m² on a solid bed (0.4 m² per kg, BAL), so a 20kg bag covers about 8 m².
How long before I can grout floor tiles?
Usually after 24 hours with standard adhesive. Rapid-set adhesives can be grouted sooner: check the bag.
Sources
Quantities are estimates for typical jobs, using the coverage figures above. Products vary, so check the data sheet for the product you buy, and talk to a professional for structural, electrical or gas work. SmartBuild is independent and not affiliated with any of the manufacturers listed.
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