01Overhang is where islands fail
A 300 mm seating overhang is normal. Under it, the plate is a cantilever with nothing below, and deflection scales with the cube of the overhang length — so 300 mm behaves eight times worse than 150 mm.
| Plate | No support | With 2 brackets | With a folded leg |
|---|---|---|---|
| 6 mm | ≈ 4.6 mm | ≈ 1.1 mm | ≈ 0.2 mm |
| 8 mm | ≈ 1.9 mm | ≈ 0.5 mm | ≈ 0.1 mm |
| 10 mm | ≈ 1.0 mm | ≈ 0.3 mm | ≈ 0.1 mm |
Read it as shape, not as a design check. The practical rule: below 1 mm nobody notices, 2 mm feels soft under a hand, and past 4 mm a glass on the overhang starts to lean. Above 250 mm of unsupported overhang we assume brackets on the drawing and say so in the quote.
Going from 6 to 10 mm plate to fix a soft overhang costs far more weight and money than two steel brackets welded under the overhang. Thickness is for the look of the edge; brackets are for the structure.
02Services, decided before the plate is cut
An island usually carries more services than a wall run, and every one of them is an aperture that has to be positioned from a datum.
- Hob. Cut-out from the appliance sheet, with the clearance to combustibles taken from the appliance maker rather than from us. Ventilation clearance underneath is often forgotten.
- Sockets. A pop-up tower needs a clear cylinder below the top, not just a hole in it.
- Sink, if the island has one. Waste and trap clearance decide whether a drawer can go under it.
- Extraction. Downdraft units need their own aperture and a duct path that fits the carcass.
We cut apertures to ±0.5 mm from your template or the appliance drawing. The ±0.05 mm number applies to a machined edge, not to a cut-out, and a supplier who quotes it for an aperture has not measured one.
03One piece or two, and how the joint is placed
At 3000 mm long, an island top is either one piece — up to 8000 mm is possible — or two pieces with a joint. One piece is stronger and simpler; it is also heavier, harder to carry through a house, and it cannot be replaced in halves.
If it is two pieces, the joint belongs over a carcass divider and nowhere else. A joint 80 mm off a divider is visible, flexible and a phone call after installation. A welded and dressed joint over a divider is nearly invisible and behaves like one piece — at a price, because dressing a weld in a No.4 grain is hand work.
04What to send for an island
Plan size, all four edge profiles, finished height, overhang depth on each side, bracket or leg positions, and every service aperture from a stated datum. Add the carcass plan if you have it: the joint and the brackets have to line up with something real.
We work in 304 or 316L, 5 to 10 mm, with a No.4 finish as standard and the grain running the long way. Quotation in 24 hours priced by line, 15 working days from a confirmed drawing, packing on-edge with the edges protected. The inspection sheet records the edge tolerance and the overall dimensions measured at a stated temperature — on a 3000 mm part that note matters, because 304 grows about 0.5 mm over that length between a cold workshop and a warm kitchen. The warranty runs against that sheet.
Countertop specification · Kitchen countertops · Integrated sinks · Send a drawing