20mm or 30mm? It's one of the first decisions we discuss with clients, and the answer is more nuanced than "thicker is better."
20mm Benchtops
20mm is the standard thickness for most kitchen benchtops. It's structurally sufficient for spans up to about 1.8 metres, which covers most kitchen bench runs. 20mm stone is lighter, easier to handle, and costs less than 30mm. For an undermount sink installation, we typically build up the edge to 40mm (two laminated layers) so the edge looks substantial from the front.
20mm works well for bathroom vanities, splashbacks and wall cladding where weight and cost matter.
30mm Benchtops
30mm stone has a heavier, more substantial look. It's often specified for waterfall ends and large islands where the edge is visible from the side. 30mm also allows longer unsupported overhangs — up to about 300mm without corbelling, compared to about 200mm for 20mm.
The trade-off: 30mm stone is significantly heavier, which means more structural support is needed in the cabinetry. It also costs more, both in material and in installation labour. We don't recommend 30mm unless there's a specific design reason — most kitchens are perfectly well served by 20mm with a built-up edge.
Our Recommendation
Default to 20mm for most kitchen applications. Go 30mm if you want waterfall ends, a large overhang, or specifically want the heavier visual weight. We'll work with your cabinet maker to make sure the support is right for whichever thickness you choose.