Choosing bathroom tiles without running short
A bathroom wall is 2.40 m wide and 1.80 m high. It contains a window 0.60 m by 0.50 m that will not be tiled. The owner has two tile options. Option A: square tiles 20 cm by 20 cm, sold in boxes of 15, €18.50 per box. Option B: square tiles 30 cm by 30 cm, sold in boxes of 10, €22.00 per box. Tiles cannot be bought singly. The tiler advises adding 10% to the number of tiles needed to allow for cuts and breakages. The owner wants the cheaper option but does not want to run short. Grout and adhesive costs are the same for both options. The wall area behind the window is not tiled, and the window is entirely inside the tiled area.
1. Calculate the tiled area and the number of tiles needed for Option A, including the 10% allowance. Then find the number of boxes and the cost.
Read the worked answer
Wall area = 2.40 m × 1.80 m = 4.32 m². Window area = 0.60 m × 0.50 m = 0.30 m². Tiled area = 4.32 - 0.30 = 4.02 m².
Option A tile area = 0.20 m × 0.20 m = 0.04 m². Tiles needed before allowance = 4.02 ÷ 0.04 = 100.5, so 101 whole tiles. Add 10%: 101 × 1.10 = 111.1, so 112 tiles.
Boxes needed = 112 ÷ 15 = 7.47, so 8 boxes. Cost = 8 × €18.50 = €148.00.
Using the area method gives 4.02 × 1.10 = 4.422 m², and 4.422 ÷ 0.04 = 110.55, so 111 tiles; this still requires 8 boxes.
2. Repeat the calculation for Option B and recommend which option to buy. Justify with costs and any practical risk.
Read the worked answer
Option B tile area = 0.30 m × 0.30 m = 0.09 m². Tiles needed before allowance = 4.02 ÷ 0.09 = 44.67, so 45 whole tiles. Add 10%: 45 × 1.10 = 49.5, so 50 tiles.
Boxes needed = 50 ÷ 10 = 5 boxes. Cost = 5 × €22.00 = €110.00.
Option B costs €110.00, which is €38.00 cheaper than Option A at €148.00. It also uses fewer tiles, so there are fewer grout lines.
Recommendation: buy Option B, provided the room layout allows large tiles to be cut sensibly around the window and corners. Larger tiles can produce more visible waste if the wall is not square, so the tiler should check the actual wall before ordering. The 50 tiles include an allowance of about 11% above the 45 needed, so the risk of running short is low.