If your basin goes into a vanity top rather than on top of it, you have three options: inset, semi-inset and undermount. They look different, they work with different top materials and they need different preparation. Here is how to tell them apart and choose the right one.
The three types at a glance
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Inset (drop-in, lavabo da incasso soprapiano): the basin drops into a hole cut in the top and its rim rests on the surface. It is the most forgiving option and works with most top materials, including laminate, lacquered wood, glass and stone.
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Semi-inset (lavabo semincasso): similar to an inset basin, but the front of the basin sticks out beyond the top and the cabinet. Because the bowl projects forward, it can sit on a shallower vanity unit than the basin itself, which is useful in narrow bathrooms. Check the technical drawing for the exact projection.
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Undermount (lavabo sottopiano): the basin is fixed under the top, with its rim below the surface. The top is cut and finished around the opening, so you can wipe water straight into the bowl. It is usually paired with stone or glass tops.
If you would rather have the basin sitting on the counter, see our guide to countertop (vessel) basins.
How to choose
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Start from the top material. Semi-inset and undermount basins are the most restrictive: they generally need a solid top such as stone or glass. A laminate top normally means an inset basin.
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Check the cabinet depth. With a semi-inset basin, part of the bowl projects forward, so compare the basin depth with the depth of your vanity unit. Ask us for the technical drawing before ordering the furniture.
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Decide where the tap goes. Some basins have a tap hole and some do not. With an undermount basin the tap is mounted on the top or on the wall. Check the tap hole for each model on the product page.
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Think about cleaning. Undermount gives the smoothest surface to wipe. With inset and semi-inset basins, keep the silicone joint around the rim in good condition.
Our inset, semi-inset and undermount basins
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Semi-inset: the FORM collection, in the 60 x 35 cm and 65 x 40 cm sizes and the round 40 cm. They come in glossy white, the matt Colore palette, the glossy I Lucidi colours and Materia marble-effect finishes.
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Inset (drop-in): the DECOR basins in three sizes (56 x 41, 57 x 47 and 64 x 51 cm). DECOR 56 has no tap hole; DECOR 57 and 63 have a single tap hole.
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Undermount: the oval TIPO (57 x 43 cm) and FILO (70 x 38 or 93 x 38 cm), and the rectangular CUBIC (54 x 41 or 85 x 46 cm), all in glossy white. They are fixed with the undermount fixing kit (FIX02), sold separately.
Browse them all in our semi-inset and inset collection.
Installing an undermount basin
Basin manufacturers' instructions follow the same basic steps:
- Turn the top upside down and mark the basin position around the cut-out.
- Run a bead of silicone along the upper edge of the basin and position it carefully against the opening.
- Secure it as described in the instructions for your fixing kit, then add a second bead of silicone along the edge to seal it.
- Use neutral (non-acetic) silicone on marble, natural stone and glass, and leave everything upside down for at least 24 hours while it cures.
The cut-out itself is made by your stone or top supplier. Give them the technical drawing of the basin, which we can send you with the product code.
Watch it done: search YouTube for undermount basin installation videos.
Drain and siphon
All these basins are supplied on their own: the tap, drain and siphon are sold separately. For the FORM semi-inset basins we recommend the colour-matched Free Flow ceramic drain or the Up and Down ceramic drain. The right drain also depends on whether the basin has an overflow, which varies by model: our guide to basin overflows and wastes explains how to choose, and you can find siphons in our accessories.
Recommended products
Sources and further reading
