Getting a kitchen island right on paper is what makes it work on installation day. Before choosing a stone or a style, the numbers need to add up: worktop depth, overhang, seating and how the finished slab will actually be supported. This guide walks through the sizing and layout decisions that shape every island we template and fit. Looking for style inspiration first? See our Kitchen Island Worktop Ideas guide, or browse our full stone collections.
Planning step one
Standard Depth & Length
Most kitchen islands sit on a base cabinet run around 600mm deep, the same depth as standard perimeter units, though the worktop itself is usually cut wider to allow an overhang on one or more sides. Larger islands with seating or a prep zone on the same run often extend to 900mm or 1,000mm deep to fit both comfortably.
Length is driven by the room rather than a fixed rule. As a general guide, a single island needs at least 1,000 to 1,200mm of clear walkway on every side so two people can pass each other, or one person can stand at an open appliance door, without feeling boxed in.
Every project is templated on site before the final cut, so these figures are a starting point for planning rather than a fixed spec. See how we confirm exact dimensions in our installation process.
Rule of thumb
- 600mm base depth is standard, 900 to 1,000mm for dual-purpose islands
- Allow 1,000 to 1,200mm clear walkway on all sides where possible
- Length is set by the room and the cabinet run beneath, not a fixed figure
- Final dimensions are always confirmed at on-site templating stage
Planning step two
Working Out Seating Numbers
The overhang needed for comfortable seating is a simple sum once you know how many people you want seated at once. Each stool needs roughly 600 to 700mm of width along the counter edge to avoid elbows colliding, and the worktop needs to overhang the cabinet below by around 300 to 400mm for knee clearance.
For four seats side by side, that means planning for a run of at least 2,400 to 2,600mm of usable seating edge. Corner or L-shaped seating arrangements can fit more people into a shorter run, but need more careful templating around the corner joint.
Longer overhangs need proper structural support, which is covered in the section below on thickness and support. For specific edge and cut-out options, see our worktop details page.
Quick numbers
- Allow 600 to 700mm of counter width per seated guest
- Standard knee clearance overhang is 300 to 400mm
- Four seats need roughly 2,400 to 2,600mm of seating edge
- Corner seating fits more people into a shorter run
Planning step three
Single Island or Double Island
Once a kitchen is large enough, a single island can start to feel like an obstacle rather than a hub. Splitting the layout into two smaller islands, one for prep and cooking and one for seating or serving, is increasingly common in larger open-plan Irish kitchens.
The trade-off is space. A double island layout generally needs a room wide enough to keep 1,000 to 1,200mm of clearance around each island independently, so the two don't end up feeling cramped between them. In narrower kitchens, a single well-planned island with a breakfast bar overhang usually works better.
Whichever layout suits the room, both islands in a double arrangement are usually finished in the same worktop material for visual consistency. Browse suitable surfaces in our stone collections.
When to consider a double island
- Room width comfortably exceeds a single island plus clearance on both sides
- You want to separate cooking and prep from seating and serving
- The kitchen is part of a larger open-plan living and dining space
- Match the worktop material across both islands for a cohesive look
Planning step four
Worktop Thickness & Support
Thickness is a structural decision as much as an aesthetic one. Quartz and sintered stone are typically specified in 20mm or 30mm, with the thicker option better suited to longer breakfast bar overhangs and larger unsupported spans.
As a general guide, overhangs beyond roughly 300mm usually call for concealed steel brackets or hidden corbels beneath the worktop, particularly in 20mm material. Sintered stone's tensile strength allows it to span slightly further than quartz before extra support is needed, but every span is checked at templating stage rather than assumed from a general rule.
The right thickness also affects how cut-outs, drainer grooves and edge profiles look once fitted. Compare finishes and edge options in our worktop details guide.
Specification notes
- 20mm and 30mm are the standard thicknesses for quartz and sintered stone
- Overhangs beyond roughly 300mm generally need bracket or corbel support
- Sintered stone can span slightly further unsupported than quartz
- Every overhang is verified for support needs at templating, not guessed
Planning step five
Why Templating Locks the Final Size
Every measurement up to this point is a planning guide, not a final spec. Walls are rarely perfectly square, cabinets settle slightly once fitted, and appliance positions can shift during the build. That's why the final worktop size is always confirmed on site, after the cabinetry is in place, not from the original kitchen plan.
Our team uses laser templating to capture the exact shape of the installed cabinets, along with the precise position of every hob, sink, tap and socket cut-out. That template, not the architect's drawing, is what the slab is cut to.
This is also the point where overhang length, seating clearance and support brackets are checked against the real room rather than the plan. Read more about the stage in our installation process.
What happens at templating
- Laser templating captures the true shape of the fitted cabinetry
- Hob, sink, tap and socket positions are measured precisely on site
- Overhang and support needs are confirmed against the real room
- The slab is cut to the template, not the original kitchen drawing
Explore further
Plan your island on notjustgranite.ie
Not Just Granite · Galway, Ireland
Get your island
properly measured
Plans on paper only get you so far. Our team templates every island on site to confirm the exact size, overhang and support it needs before a single slab is cut. Visit our Galway showroom or get in touch to arrange your measurement.
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