01The three joints, side by side
Everything else on this page follows from one of these three constructions. Pick the joint first; the price and the drawing follow from it. We weld bowls into 5–10 mm plate, and we also cut apertures for bowls you supply — which of the two you get should follow the joint you want, not the grade of plate that happens to be on the rack.
| Method | What it looks like | Drawing impact | Where it fails |
|---|---|---|---|
| Welded-in bowl | The bowl is fabricated into the plate; no rim, no silicone | Bowl geometry, radii and drain position all on the drawing | A weld that was polished too hard thins the wall |
| Undermount | Plate has an aperture; bowl fixed from below on clips or studs | Aperture size and position to the sink template | Clip tension and a silicone line that is never inspected again |
| Top-mount / drop-in | Bowl sits on the plate with a rolled rim and a bead | Aperture plus clearance for the rim | The bead: it traps water and eventually discolours |
On thin sheet, undermount is the normal answer, because welding 1 mm into a flat top distorts it. On 5–10 mm plate the distortion behaves differently — the plate has enough mass to hold shape while heat is put into it — which is why a welded bowl is a plausible spec at this thickness and not at 1.2 mm.
02Basin layout: where the bowl actually sits
Bowl or basin — the same part, named differently on each side of the Atlantic. The joint decides how it meets the plate; the layout decides whether the top works once it is on the bench, and layout is the part of the drawing that comes back most often.
- Position it from a datum, not from “centred”. Write 430 mm from the left end and 120 mm from the front edge, and say which end and which edge. A bowl centred in the top is not centred over the cabinet once the run includes a filler panel.
- Bowl size against top depth. On a 600 mm deep top a 450 mm bowl leaves 150 mm of deck for the mixer and the wall joint. Take the bowl to 500 mm and the tap stands where the tap should not be.
- Double bowls need a stated divider. The dimension that matters runs from the datum to the divider, not from one bowl edge to the other.
- Drain position. A drain set to the rear keeps the trap out of the cabinet, which is what makes a drawer stack work under a sink. Say which way the trap runs.
None of this is exotic and all of it is free at drawing stage. It is expensive after the aperture is cut — the cut-out dimensions page sets out what a re-cut costs in plate and in time.
03Drainer, drainboard and workstation tops
A drainer is where the water leaves the bowl, and there are four ways to build one. Only the first two leave no joint to seal.
| Method | What it is | Joint it adds | Where it costs |
|---|---|---|---|
| Folded into the sheet | Flutes or slots pressed into the same plate, falling towards the bowl | None | Press time; the pattern is fixed once it is tooled |
| Channel into the bowl | A slotted channel formed in the deck that drains into the bowl | None | Fold sequence; it needs a clear fall and a clear drain path |
| Tray dropped in | A separate stainless tray sitting in an aperture | Aperture and rim | The rim traps water, and there are two more edges to seal |
| Boards on a ledge | A machined or folded ledge that takes a board over the bowl | None | Ledge depth and plane have to be stated |
The last row is what the trade calls a workstation top: a chopping board or a colander sits on a ledge over the bowl, so the same footprint is prep space or washing space. Two numbers make or break it. The ledge has to be wide enough for the accessory and deep enough that the board does not see-saw, and the ledge plane has to be level while the drainer around it falls towards the drain.
Any drainer formed in the sheet needs a fall of a millimetre or two across its length. On solid plate that fall is put in by the press brake; it cannot be shimmed in on site. That is why the drainer belongs in the quote and not in a site decision. If the top sits on a frame instead of on cabinets, the same decision is on the sink bench page.
04A sink run we built, and what it shows
The argument above is easier to trust with a photograph of a bowl that is actually in a top. Both frames are from our own showroom stand, shot close enough to judge the joint.
Two things to look at. The bowl has no rim standing on the surface, so there is no bead to clean around at the edge of the aperture. And the deck continues past the bowl to the end of the run in one plane, which is what a fabricated joint buys you and what an undermount cannot: on an undermount the plate stops at a cut edge and the bowl hangs below it.
To be straight about the evidence: these are stand photographs, so they prove the construction and not the installation. They are also not offered as proof of the edge tolerance quoted elsewhere on the site — that is measured on a machined plate edge, not inferred from a picture. For the installed version, the project photographs show a run on site with the difference between the two kinds of frame labelled.
05Welded-in bowl: what it costs you
A welded bowl has no rim, no silicone and nothing to catch dirt. It is the detail that makes a photograph of a commercial kitchen look expensive, and it is the one buyers ask for before they ask the price.
What it costs is time and tolerance. The bowl has to be fabricated from sheet, welded into the plate, the weld dressed back flush, and the finish re-grained across the joint so it does not show as a halo. Every one of those steps is a chance to distort flat plate — and once a top has been through that, the flatness is no longer the mill flatness on the countertop specification, it is the fabricator's.
Our own rule on these: we will not quote a welded bowl without the bowl geometry, because the radius at the bottom corner is what decides whether the weld can be dressed invisibly. A tight radius in 2 mm sheet welded into 8 mm plate is a different job from the same radius in 1.2 mm.
The realistic question is not “can you weld it”, it is “what does the finish look like across the weld when it is done”. Ask for a photo of a finished joint in the same grain direction you are specifying, at the same lighting, before you approve the order.
06One-piece tops, and when they are not the answer
“One-piece” is used for two different products, and the confusion costs money.
The first is a drawn or pressed unit: bowl and a small deck pressed from one blank, sold in catalogue sizes, usually 0.8–1.2 mm thick and stiffened underneath. It is a sink unit rather than a countertop. Where the size on your drawing happens to match a catalogue size, it is the cheapest way to get a bowl with no joint in it.
The second is what we make: a fabricated one-piece top. The bowl is built from sheet and welded into the plate, and the plate is 5–10 mm solid stainless. Any length, any bowl position, any corner radius — which is the whole point of the custom route. The joint is dressed back and re-grained, so from above there is one surface and nothing standing on it.
When the drawn unit stops being the answer: the top is longer than the catalogue, the bowl is offset from centre, the plate has to be thicker than 2 mm for a commercial kitchen, or the bowl may have to be serviced later. Those four cases are common, and all four mean fabricated.
The honest cost of fabricated is weight. A 2400 × 600 mm top in 5 mm plate is over 50 kg of stainless before the bowl goes in, so it takes two people to lift and a frame designed to carry it. Say so early: it changes the cabinet, not just the top.
07Undermount: the aperture is the whole job
Undermount is the cheapest of the three and the one most likely to be wrong, because the aperture is cut from a template that has to match a bowl you may not have on site yet.
- Cut to the sink maker's template, not to the bowl. The template includes the clip clearance; the bowl does not.
- State the datum. “Centred” is not a dimension. Position the aperture from the front edge or from a fixed end, and say which.
- We hold ±0.5 mm on a cut aperture. The ±0.05 mm edge tolerance applies to a machined edge, not to a plasma or waterjet aperture — anyone quoting ±0.05 mm on a sink cut-out is quoting a number they cannot inspect.
- Substrate or no substrate. On 5 mm plate, a large aperture in a 600 mm deep top removes most of the stiff middle. Tell us the bowl size; we will say whether the plate needs a doubler.
08Top-mount: when it is the right answer
Top-mount gets dismissed as the cheap option. It is also the only one you can replace without removing the countertop, which is a real advantage in a rental, a serviced kitchen, or a commercial fit-out where the bowl will be beaten up in five years.
The cost is the rim. A rolled rim on plate reads as a ledge, and the bead behind it is where water sits. If the top is going into a hygiene-inspected kitchen, that bead is the first thing a torch will find.
Where top-mount wins outright: stainless tops over an existing carcass where the bowl has to be serviceable, and any job where the sink model is not final at the time of order.
09What we need on the drawing
For any of the three, the same five things:
- Overall top size, in millimetres, with the datum edge marked.
- Aperture or bowl position from that datum, in both directions.
- The sink: model number, template PDF, or a measured drawing of the bowl.
- Joint method — welded, undermount, top-mount — stated, not implied.
- Drain and overflow position if the bowl is being fabricated.
Send those and the quote comes back in 24 hours with the joint method priced as a line item, so you can see what the weld actually costs against the clip.
Send a drawing · Countertop specification · Commercial kitchens