Bathroom vanity unit and basin: dimensions and choices

A bathroom is designed around a single dimension: the height of the vanity top, measured from the finished floor, with the tiling laid. The contemporary reference is 85 cm. Older units were fitted at 80 cm, a height inherited from a time when people were shorter and leaned further over the basin. Today, 85 cm avoids bending your back and suits adults from 1.60 m to 1.85 m.

The trap starts with the countertop basin. A basin sitting on the top adds 10 to 15 cm: if you keep the top at 85 cm, the upper rim of the bowl rises to 95 or 100 cm, which becomes uncomfortable for washing your face and impossible for a child. In that case, I drop the top to 75 to 80 cm to get back to a workable working height.

The rule I apply: what matters is not the height of the unit, it is the height of the upper rim of the basin, which should sit between 85 and 90 cm.

These dimensions are fixed at design stage, not at installation stage. That is why I position the water supply points and light fittings from the design package onwards, just as for the other technical rooms described in my guide on the villa floor plan.

The choice of basin type has direct consequences for the height of the unit, for cleaning and for the budget. I always settle it before designing the unit, never afterwards.

In apartment renovations, I favour the undermount basin or the one-piece basin top: no exposed horizontal joint, so no blackened silicone after two years. The countertop basin still looks superb in a master suite, provided you accept a lower top and cleaning around the base.

Also pay attention to the matching tap. A tall countertop basin calls for a tall or wall-mounted mixer: a standard mixer with a 12 cm spout discharges inside the bowl and makes washing your hands impossible. This basin/tap compatibility should be checked on the technical data sheets before ordering.

A wall-hung unit looks good, makes floor cleaning easier and visually lightens a small bathroom. In return, it demands real thought about the wall structure, because it works in cantilever.

The calculation is simple to set out: a 120 cm carcass with a stone top already weighs 60 to 120 kg empty. Add the water in the basin, the contents of the drawers and the weight of an adult leaning in to shave, and the fixing has to take 150 kg or more, with a pull-out force at the top of the brackets.

• Concrete or solid block wall: metal anchors or chemical anchoring, with no particular difficulty.
• Hollow brick: long expansion anchors or chemical anchoring with sleeves, never standard plastic plugs.
• Plasterboard partition: reinforcement is mandatory, installed before the partition is closed up. A metal noggin between studs, or an 18 to 22 mm plywood or OSB panel screwed to the framing, across the full width of the future unit and to a height of at least 40 cm.
• Lining on a load-bearing wall: pass through the lining and fix into the wall, using spacers so as not to crush the insulation.

Two details complete the picture: a clearance of 20 to 25 cm under the unit for the mop and for a visually light result, and a waste outlet roughed in at the right height. The trap of a wall-hung unit should stay out of sight, which means a wall outlet between 45 and 55 cm from the floor, offset from the basin centre line where a low drawer is planned.

These decisions belong to the construction drawings. On a renovation site, I settle them with the plumber before the tiling goes down: afterwards, every correction means broken tiles.

Here are 2026 ballpark figures for the package of "unit + top + basin + taps + lit mirror", excluding plumbing, tiling and labour. These ranges vary considerably from one supplier to another and should be confirmed by quotation.

The order of decisions matters more than the budget. My sequence is: layout and clearances, then basin type, then top height, then water and electrical connections, then material choices, and only then the design of the unit and its storage. Taking these steps in the wrong order is the most common cause of rework on site.

For a single bathroom, an on-site assessment is often enough: for between 1,500 and 2,500 MAD, I take the measurements, confirm feasibility and hand over the layout principles with the heights to be respected. For a full apartment or villa renovation, an interior architecture assignment runs between 10 and 20% of the works budget, depending on the level of detail and the site supervision required. The details are set out on the fees page, and the question of the scope of the assignment is covered in my guide on architect or interior architect.

One useful regulatory point: refitting a bathroom like for like, without touching the structure or the facades, does not require any authorisation. As soon as you move load-bearing walls, create an opening or change the floor area, an application becomes necessary: in Morocco, submissions go through the Rokhas platform and require the signature of an architect registered with the national Order of Architects, in accordance with law 016-89. The steps are set out in the guide on the building permit in Morocco.

Tell me about your bathroom

If you are torn between a single and a double basin, between a countertop basin and a one-piece top, or if you do not know whether your partition wall can carry a wall-hung unit, send me the dimensions of the room, one or two photos and how it will be used. I work on architecture projects in Casablanca and architecture projects in Rabat, both new build and renovation. You can reach me on +212 661 25 78 84 or through the contact page, and browse the projects as well as the other guides.