How much tile wastage should you allow?

Tile wastage is the extra material ordered above the measured area to cover perimeter cuts, breakage during handling and laying, and the spares kept back for later repairs. It is expressed as a percentage added to the net area, and it is a real cost on the order rather than a rounding convenience — on a large-format job the wastage line can be a meaningful share of the tile spend.

The lay pattern is the biggest driver, because it decides how much of each cut tile can be reused. A straight grid lay is the most economical and conventionally carries about 10%. A 50% brick-bond offset runs slightly higher, around 12%, because the rows start alternately. A diagonal lay is around 15% — every perimeter tile is cut at 45 degrees and the offcut rarely fits anywhere else. Herringbone is the expensive one: Australian retailers publish 20% at minimum and some quote 30%, because the pattern cuts two tiles at every edge.

Two adjustments sit on top of the pattern figure. Large-format tiles increase waste, because a cut takes a bigger piece out of stock and the offcut is less likely to fit another gap — a couple of percent is the usual allowance for tiles with a side of 600 mm or more. Small rooms increase it too, because a bathroom is almost all perimeter and there is little uncut field to absorb the cuts; adding around 5% under about 3 m² is a common rule.

Room shape matters more than a percentage can express. An L-shaped room, or one with several fixed obstacles, generates more cuts than a plain rectangle of the same area. Counting the tiles on the actual grid rather than dividing the area — whole tiles along each axis, cut tiles counted whole — is the more accurate approach for narrow runs, and it is what an estimating tool should do when it knows the room dimensions rather than just the area. The tile and grout estimator applies the pattern allowance and both modifiers for a single room.