Tile cracks, edges need cutting, and some pieces end up too small to use. People buy extra for two different reasons, and it helps to keep them separate: waste during installation, and spares for repairs years later.
What MSI publishes
MSI Surfaces, a tile manufacturer, suggests buying at least 10% extra to keep on hand, about 15% for tile with a fancy shape or pattern, and more for a diagonal layout. It also notes large tiles are more delicate and are worth a little extra. The company’s own pages are not fully consistent on diagonals, which is a good reason to treat any single percentage as a starting point.
Armstrong’s estimating chapter for commercial flooring makes a point that applies to any room: the allowance is larger for small rooms than for big ones, because the edges are a bigger share of the floor.
Raises the allowance
- Diagonal layouts and patterns that must line up
- Small rooms and rooms with many cuts
- Large-format tile, which breaks more and wastes more per cut
- Mosaic and shaped tile, which come in more variations
- Wanting spares for a repair later
What the allowance does to the box count
For a 12 × 14 ft floor and boxes covering 16 sq ft:
| Allowance | Area required | Calculated | Buy |
|---|---|---|---|
| 5% | 176.4 sq ft | 11.03 boxes | 12 boxes |
| 10% | 184.8 sq ft | 11.55 boxes | 12 boxes |
| 15% | 193.2 sq ft | 12.08 boxes | 13 boxes |
| 20% | 201.6 sq ft | 12.6 boxes | 13 boxes |
Step from 12 boxes to 13 boxes between the lowest and highest allowance. Because tile comes in whole boxes, some steps in the allowance do not change the order, while others add a box.
Setting your own
Start with the manufacturer’s installation guide for your tile, which sometimes gives a figure. Otherwise choose an allowance for your pattern and tile size, keep it editable, and look at the supplied area as well as the box count. A box or two of spare from the same production batch is also worth having if you may need a repair, because later batches can differ slightly in color.