Quick answer
An island taking both a sink and a dishwasher needs to be about 2100mm long minimum and 900mm deep. The dishwasher takes a 600mm bay, the sink cabinet another 600 to 900mm, and you need working bench either side. Allow 1000mm clearance all round, and 1200mm on the side people walk past while the dishwasher is open.
Key points
- 2100mm long and 900mm deep is the realistic minimum for sink plus dishwasher.
- 1000mm clearance around the island, 1200mm where a dishwasher door opens into traffic.
- Seating needs 300mm of overhang for knees and 600mm of width per person.
- A sink in an island means waste and supply through the floor. That is the expensive part, not the cabinetry.
- 900mm deep is the sweet spot. 600mm looks mean and anything past 1100mm you cannot reach across.
Islands are where kitchen plans go wrong most often, because they are drawn to fill a gap rather than sized from what has to fit inside them. Once you put a sink and a dishwasher in one, the island stops being a bench and becomes a cabinet run with fixed minimum dimensions.
Working out the length
Add up what has to go in it, and do not forget the bench you need either side of the sink.
| Element | Width needed | Why |
|---|---|---|
| Dishwasher bay | 600mm | Standard NZ dishwasher width. 450mm for a slimline |
| Sink cabinet | 600 to 900mm | 600mm for a single bowl, 900mm for a bowl and a half |
| Bench beside the sink | 400mm minimum | Somewhere for the draining and the dishes waiting to go in |
| Bench on the other side | 300mm minimum | Otherwise the sink runs straight into the end panel |
| End panels | About 20mm each | Finished ends on an island are visible from three sides |
That gives roughly 1900mm as an absolute floor and about 2100mm as the number to design to. If you also want seating, add 600mm of clear length per seat, so a two-seat island with a sink and dishwasher is realistically 2700mm or more.
Depth, and why 900mm
A 600mm island is just a bench that has come away from the wall, and it looks like one. At 900mm you can run 600mm of cabinetry on the working side and still have 300mm on the other side for an overhang, a power point run or simply somewhere to put things down that is not in the cook's way.
Past about 1100mm you cannot comfortably reach the far side to wipe it, which sounds trivial until you have lived with it. Very large islands generally work better with storage accessed from both sides rather than one deep bench.
Clearances around it
| Side | Clearance | Why |
|---|---|---|
| Working side, one cook | 1000mm | Enough to open drawers on both the island and the run behind |
| Working side, two cooks | 1200mm | One person can pass behind the other while a drawer is open |
| Where the dishwasher opens | 1200mm | An open dishwasher door takes about 600mm, and someone still has to get past |
| Seating side | 1000mm minimum | Enough to pull a stool out and stand up |
| Ends | 900mm | Enough to walk round rather than back out |
Seating on an island
Overhang is the number people get wrong. You need 300mm of clear overhang for knees at bench height. Less than that and people sit sideways. That overhang has to be supported once it goes past about 300mm in stone, so factor in brackets or a leg, and remember the overhang comes off your walkway on that side.
Allow 600mm of length per seat. Three stools on a 1500mm island is two stools with a squeeze in the middle.
A note on drawing it before you buy it
An island is the one part of a kitchen where paper lies to you. It always looks fine in plan and often does not survive contact with a dishwasher door and a person. Setting it out in three dimensions before you commit, with the real bench depths and the real clearances, is worth the half hour.
Frequently asked questions
How big does an island need to be for a sink and dishwasher?
About 2100mm long and 900mm deep. The dishwasher takes 600mm, the sink cabinet 600 to 900mm, and you need working bench either side of the sink.
How much space do you need around an island?
1000mm on the working side for one cook and 1200mm for two, and 1200mm on any side where the dishwasher door opens into a walkway.
How much overhang for seating?
300mm of clear overhang at bench height, and 600mm of length per person. Anything less and people end up sitting side-on.
Is it expensive to put a sink in an island?
The cabinetry is not, the plumbing is. Waste and supply have to run through the floor, and on a concrete slab that means cutting and re-pouring. Price that before the cabinetry.
How deep should an island be?
900mm is the sweet spot: 600mm of cabinetry on the working side plus 300mm the other side. 600mm reads as a stranded bench, and past 1100mm you cannot reach across it.
Can I have a cooktop in the island instead?
Yes, and it needs extraction, which either means a ceiling-mounted hood or a downdraft. Both cost more than a rangehood on a wall, so it is a decision to make early.