1800mm Double Vanity with Undermount Basins and Stone Top

Fit an 1800mm double cabinet with undermount basins and a stone benchtop and you move from a builder's-standard vanity into something closer to joinery. The bowls sit below a single slab, so the whole top wipes down in one pass. This guide explains what that combination changes and what to check.

What undermount basins change

An undermount basin is fixed beneath the benchtop instead of dropping in from above, so there’s no rim sitting on the surface to catch grime. You can sweep water and dust straight into the bowl, which is the main reason people choose them. They only work with a solid top that can be cut and polished around the opening — which is where the stone comes in.

Choosing the stone top

A stone benchtop across an 1800mm span needs to be flat, well supported and sealed at the cut-outs. Engineered stone is the usual pick for bathrooms because it’s dense and consistent, though natural stone is an option if you’ll keep the sealing up. Either way, confirm the top is templated to the exact cabinet and basin positions, since the undermount cut-outs are made before the slab arrives, not on site.

Tapware and drainage

Because the basin sits low under a thick top, the tap spout has to clear the extra height and still reach into the bowl. Check the spout projection and height against the top thickness before ordering tapware. With two basins you’ll also need two waste and two water connections roughed in at the right spacing for the undermount positions.

See stone-top vanities in person

Renovating on the NSW South Coast? A stone-topped unit is worth seeing before you order — you can view the range of bathroom vanities at Just Bathrooms, a local showroom, to compare tops and basin styles.