Three numbers, one name

Ask five people on a project for "the vanity height" and you will get three different numbers, all correct, none compatible.

Carcass height. What the factory quotes, and what appears on the cut sheet. A wall-hung unit is typically 450–600 mm tall, because it hangs on a wall and carries drawers rather than a floor.

Countertop height. The structural surface, usually the top of a 20 mm engineered stone slab. In some specifications this is called the vanity height because it is the last thing the joiner is responsible for.

Finished height. The surface a person actually stands at, which includes the countertop and, where fitted, the rim of a basin sitting on top of it. This is the only one of the three that a guest experiences.

The gap between the first and the third is where projects lose control. A drawing dimensioned at 800 mm — a common minimum for a wall-hung carcass — arrives at 820 mm with a 20 mm top, and at 940 mm with a vessel basin standing 120 mm proud. Nobody has made an error. Three people have each been correct about a different object.

So the first useful sentence in any vanity specification is not a number. It is a definition: all heights to be read to the finished top surface, inclusive of countertop and basin rim. Everything after that sentence is arithmetic.

Reference heights by market

There is no single international standard. There are three regional conventions, one accessibility rule, and a large amount of local habit, and they disagree by up to 100 mm.

Two observations from that table are worth carrying into a design review. The first is that the European and North American ranges overlap only at their extremes: 850 mm is 33.5 in, which sits at the top of the American range and the bottom of the European one.

The second is that the accessible figure is the only one of the six that is enforceable. Everything else is convention, which means it is negotiable, which means it will be negotiated at the point where it is most expensive to change.

How the finished height accumulates

This table is the one worth pinning to the wall. It takes four common build-ups and shows what each delivers, using dimensions that appear on real drawings.

The wall-hung row deserves a note, because it is the case people misread. A wall-hung unit does not accumulate from the floor at all: its height is set by the fixing rail and the bracket, so the carcass dimension is a depth and a width question, not a height question. Which means the number that matters on a wall-hung drawing is the height of the top surface above finished floor, dimensioned explicitly, and the height of the fixing rail below it.

On floor-standing units, the plinth is the adjustment. Adjustable feet typically give 10–20 mm of range, and that range is the only thing standing between a screed that ran 8 mm proud and a cabinet that will not sit level. Specify the range, and specify that the plinth is scribed to the floor rather than left with a shadow gap — a 10 mm gap under a plinth in a wet room collects water and is the first place a floor fails.

Depth, and why the basin decides it

Depth is quoted second and matters more. It sets how far a person leans, where the tap lands relative to the bowl, and whether the door can open past the room's clear width.

Two rules follow from the table, and both are cheap to apply.

First, the basin centre determines the tap position, and the tap position determines the splash. A basin whose centre sits closer to the front edge than about a third of the unit depth will throw water forward when the tap runs at full flow and the user's hands are under it. On a 450 mm unit with a 430 mm basin, that third is 150 mm, and the basin centre needs to be behind it.

Second, countertop overhang is not decoration. Specify 20–30 mm at the front, which keeps drips off the cabinet face, and zero at any side that meets a wall, where a gap becomes a silicone joint that fails. On a wall-hung unit, an overhanging top also hides the fixing line, which is the difference between a design and a bracket.

Where the top and the bowl are machined from one slab — the arrangement we describe in Can You Use Travertine in a Shower? — the basin position is fixed at the machine rather than on site, and the overhang is decided in the shop drawing. That removes the most common depth error from the list before it can happen.

Where the "standard" comes from

The numbers above are not arbitrary, they are a compromise around a body. Working height is conventionally set about 100–150 mm below standing elbow height, which for an adult of average height lands near 850–900 mm.

The compromise is visible the moment you use the formula on real people. Elbow height varies by roughly 60 mm per 100 mm of stature, so a 1500 mm user and a 1900 mm user are 240 mm apart in comfortable counter height — a quarter of a metre, and far more than the 50 mm that separates the European and American conventions.

The figures in Table 4 are approximations from anthropometric data Estimate — verify; replace them with the dataset your market recognises if the number will be argued about. The direction holds regardless: one standard height is wrong for most of the population by a margin larger than the gap between national conventions.

Which is why the residential answer is usually 850–870 mm with a taller-than-standard mirror, and the hospitality answer is different — see below.

What hotels actually build

Hotel bathrooms settle at 850–900 mm for reasons that have nothing to do with guest comfort and everything to do with operations.

Cleaning. A wall-hung unit at 500 mm underside clearance lets a mop pass underneath, which a floor-standing unit with a 100 mm plinth does not. That single dimension decides the housekeeping minutes per room, multiplied by 120 rooms and 365 nights.

Luggage and laundry. The counter gets loaded, sat on and occasionally stood on. The fixing detail, not the height, is what survives that — a load question that belongs with the wall.

Guest height distribution. An international operator cannot optimise for one stature, so it picks a number near the middle and accepts that tall guests stoop. 850–870 mm with a generously sized mirror above it is the compromise most brands land on.

Standardisation across a portfolio. Once a brand manual says 850 mm, every refurbishment for a decade measures against it, and a 15 mm change in a new-build prototype becomes a portfolio-wide discrepancy later.

None of that says anything about what the carcass is made of, which is a separate compliance question with its own answers — the ones set out in Is E0 the Same as CARB P2?

If you take one number from this article: specify the finished height, in millimetres above finished floor level, on the vanity drawing and on the mirror drawing, and make both refer to the same datum. Most vanity height failures are datum failures wearing a millimetre costume.

Accessible installations

Where accessibility applies, the rule changes shape, and it is worth quoting precisely because it is the one figure here with legal force.

Under the 2010 ADA Standards, a lavatory is installed so that the front of the higher of the rim or counter surface is no more than 34 in (865 mm) above the finished floor Standard. The wording matters twice over. It is the front, not the back, so a top that slopes or a basin set forward changes the answer. And it is the higher of rim or counter, which is exactly the clause that vessel basins collide with: a 34 in counter with a 120 mm vessel puts the rim at 38.7 in and the installation out of compliance, with every individual component compliant.

The associated clearances are equally specific: knee clearance 27 in (685 mm) high minimum, 30 in (760 mm) wide minimum, 11 in (280 mm) deep at 9 in above the floor and 25 in (635 mm) deep at 27 in; a clear floor space for a forward approach; and insulated or otherwise protected plumbing under the unit Standard. Check the current edition and your local adoption — ADA is a US baseline and many jurisdictions layer their own requirements on top.

What this produces in practice is a vanity at 810–840 mm to the counter with an undermount basin and no vessel anywhere in the accessible room. Which is also, conveniently, a good vanity for a shorter user and for a child.

The interfaces that move the number

Four things routinely move a vanity height after the drawings are issued, and all four arrive from outside the joinery package.

• The screed. Structural slab to finished floor can be 50 mm or 150 mm, and it can vary across a room. A cabinet dimensioned from slab level arrives at the wrong height everywhere. Set the datum from finished floor, and require the screed tolerance in writing before the units are released.
• The mirror rough-in. The bottom edge of the mirror is conventionally set 150–200 mm above the vanity top, which means the vanity height sets the mirror height. If the vanity grows by 60 mm at handover, the mirror is already drilled. This is the most common late conflict in bathroom packages and it is entirely avoidable: dimension the mirror from finished floor, not from the vanity. The mirror carries its own requirements too, which is the subject of What CRI and Kelvin Should a Bathroom Mirror Use?
• The tap. A tall mixer needs vertical clearance; a wall-mounted tap needs the spout height set relative to the bowl, not the top. Both are decided by the basin chosen, and the basin is often chosen after the vanity is ordered.
• The tile set-out. A 600 mm module rarely divides into an 850 mm height. Either the tiling is set out from the vanity line or the vanity is set out from the tiling, and somebody has to decide which — on the drawing, before the first tile is fixed.

None of these is a manufacturing problem. All four are interface problems, which is the recurring pattern in every specification failure worth writing about: the product is procured as a unit and delivered into a stack of trades, and the seams between the trades are where the dimension goes missing.

How to write the dimension

Six lines, written as requirements rather than descriptions.

1. Define the datum. "All vanity heights measured to finished top surface above finished floor level, inclusive of countertop and basin rim."
2. Give one number, plus a tolerance. 870 mm ± 5 mm, not "approximately 850–900". A range invites each trade to pick the end that suits it.
3. Dimension the mirror independently. Bottom edge at 1050 mm above finished floor, not "200 mm above the vanity".
4. State the plinth adjustment range and require the plinth to be scribed to the finished floor.
5. State the depth and the front overhang separately — 500 mm carcass, 520 mm top — and confirm the clear circulation width that remains.
6. Where accessibility applies, quote the clause, not the intent. Name the standard, the edition and the 34 in limit at the higher of rim or counter, and prohibit vessel basins in accessible rooms.

One clause more, and it is the one that saves the most money: no change to basin type after the vanity is released without re-issuing the height calculation. The 120 mm vessel is ordered as a design decision in week two and arrives as a dimensional change in week twenty, and by then the mirror is on the wall.

How we hold it in production

Vanity height is easy to draw and hard to repeat, because it depends on three components that are usually made by three parties. We build bathroom vanities complete — carcass, top and basin — which collapses that problem into one set of shop drawings.

• Finished height dimensioned on the shop drawing, with carcass, top and basin listed as separate lines that sum to it. Any change to one re-issues the sum. Bergoto detail — verify
• Basin and top machined together for integrated units, so the bowl position relative to the tap drill is fixed at the machine rather than at assembly.
• Adjustable feet with a declared range on floor-standing units, and a scribed plinth detail supplied as standard rather than as an extra.
• Room-by-room dimensional schedule for project work: heights, depths, basin model and tap drill position per room type, issued before production and checked against the site datum at first delivery.

Bergoto is an OEM and ODM manufacturer of bathroom and kitchen products, operating to ISO 9001 quality management and BSCI social compliance, with around thirty years in the industry, ten production lines and annual capacity of roughly 500,000 pieces. Fifteen designers work on product development and project documentation in-house. On a hotel package that usually means one dimensional schedule covering vanity, mirror and accessories instead of three packages each dimensioned from a different assumption.

If you are setting out a bathroom package, send the room types and the finished floor datum. We will return a dimensional schedule with the height stack written out per room, and flag the rooms where the basin the design wants will not fit the depth the plan allows — before the joinery is released.

About these figures

Heights are the easiest thing in a specification to get challenged, so here is what each number rests on.

• Standard — the 34 in (865 mm) maximum, the knee clearance dimensions and the forward-approach clear floor space are from the 2010 ADA Standards for Accessible Design, lavatories and sinks. Verify the edition adopted in your jurisdiction and read the clause in the standard itself; several jurisdictions modify it.
• Estimate — verify — the 850–900 mm European range, 800–850 mm UK range, 32–36 in North American range and 450–600 mm depth ranges are trade conventions assembled from practice, not mandatory dimensions. They are what good projects build, not what any law requires.
• Estimate — verify — the elbow heights in Table 4 are approximations from anthropometric data, and the 100–150 mm working-height offset is guidance rather than a standard. Replace both with the dataset your market recognises if the figure will be argued in a meeting.
• Arithmetic, not estimate. Every finished height in Table 2 is a sum of the three stated components. Given the same inputs, anyone will reproduce the same total — which is precisely why the table is worth sending to a client.
• Bergoto detail — verify — the dimensional schedule, the declared feet range and the scribed plinth are our standard project deliverables. Confirm against the specification sheet for a specific model before quoting them in a contract.

None of this replaces a project-specific dimensional review. Heights interact with the accessible route, the door swing, the mirror position and the waterproofing upstand, and the last word belongs to whoever carries the design responsibility for the room.

Frequently asked questions