01The numbers by market
| Market | Typical | Note |
|---|---|---|
| Australia / NZ | 900 mm | Joinery convention; benchtop sits on the carcass |
| United Kingdom | 900 mm | Same convention, worktop terminology |
| United States / Canada | 36" (914 mm) | Carpentry convention; often quoted as 36 in finished |
| Accessible / ADA | 34" max (864 mm) | Where a work surface must be usable from a seated position |
| Laboratory | 900 mm standing | Lower where the bench is used seated |
The 36-inch convention and the 900 mm convention are 14 mm apart. That is small enough to be invisible in a drawing and large enough to be felt by the person who has been standing at it for eight hours — and it is the reason a spec sheet that mixes the two is worth querying.
02Height is a carcass decision, not a top decision
The finished height is what the user stands at. What the cabinet maker needs is the height at the top of the carcass, which is:
carcass height = finished height − plate thickness
At 900 mm with a 5 mm top, the carcass is 895 mm. With a 10 mm top it is 890 mm. Nobody builds an 890 mm carcass by accident — it has to be decided before the joinery is cut, which is why we ask for both numbers.
| Plate | Carcass height | Difference |
|---|---|---|
| 5 mm | 895 mm | — |
| 6 mm | 894 mm | 1 mm lower |
| 8 mm | 892 mm | 3 mm lower |
| 10 mm | 890 mm | 5 mm lower |
If a kitchen is being retrofitted and the carcass already exists, the thickness choice can push the finished height past the comfortable band. In that case the usual fix is 5 mm plate with a folded edge rather than 8 mm — same strength at the front, 3 mm saved in height.
03Why 900 mm, and when to break it
900 mm is a compromise that suits a person around 1.70–1.75 m doing general work. It is too high for a shorter person chopping and too low for a taller person washing up — the two tasks want different heights, which is why serious kitchens use different levels for different zones.
- Chopping zone: lower, around 850–880 mm, so the shoulder is over the work.
- Sink zone: higher, around 920–950 mm, so the back is not bent into the bowl.
- Hob zone: standard 900 mm, set by the appliance, not by ergonomics.
Where a top is cut in one plane at one height, 900 mm is the safe answer and the one every cabinet maker quotes without being asked.
04What to write on the drawing
Give us the finished height and the carcass height. If they disagree by more than the plate thickness, we will flag it before cutting — it is a two-line email that saves a rebuild.
Two more numbers belong on the same drawing, because they are decided at the same moment. The grade — 304 for a dry domestic kitchen, 316L where chlorides sit on the surface — and the tolerance on the edge you actually want measured, which is ±0.05 mm at a machined edge and not on a fold. Height, thickness, grade and tolerance are four separate decisions and only one of them is about millimetres.
We quote in 24 hours, hold a lead time of 15 working days from a confirmed drawing, cut and machine and weld and grain in one building, and pack on-edge with the edges protected. Our parts ship with the inspection sheet, and that record is what the warranty refers to if a dimension is ever questioned.
Benchtops, AU and NZ conventions · Countertop specification · Send a drawing