Undermount, drop-in or flush-mounted sink in a stone countertop
An undermount sink is fitted from below: the countertop runs right to the edge of the cut-out, so you sweep crumbs straight into the bowl. A drop-in sink sits with its rim on the countertop. It is simpler and cheaper to fabricate, but dirt collects along the rim. A flush-mounted sink sits level with the stone and needs the most precise routing.
Undermount sink
It is fitted to the underside of the countertop with structural adhesive and brackets. The stone runs right to the edge of the cut-out, with no rim.1 You sweep crumbs and water straight into the bowl. The edge of the cut-out has to be polished, and the stone around it reinforced with rods set in resin so it does not crack in narrow sections.1
Drop-in sink
The bowl goes into the cut-out and the rim rests on the countertop. Fabrication is simpler, because the edge of the cut-out is hidden. But dirt and water collect along the rim, and the seal needs refreshing from time to time.
Flush-mounted sink
The sink rim sits in a routed rebate, level with the stone surface. It looks the cleanest, but it needs very precise fabrication and a sink designed for this kind of fitting.
Which stone for which sink
Granite handles cutting the opening and polishing the edge best. Quartzite does too, but it needs good tools. Marble is more brittle when cut, and sintered stone is the hardest to work.1
What to choose
- Easy cleaning and a clean look: undermount.
- Simplicity and lower fabrication cost: drop-in.
- A minimalist kitchen and sintered stone: flush-mounted.
We need the sink model before we measure. For an undermount sink, it is best to have it on site.
(Sources)
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Dynamic Stone Tools, Sink Options for Stone Countertops: Undermount, Drop-In and More
(Questions)
Can an undermount sink come loose?
Not if it is fitted properly with structural adhesive and brackets. The stone around the cut-out is reinforced with rods set in resin.
Which sink works as an undermount?
One with a flat, even flange all around the bowl. That makes bonding and fixing easier.
