Build a Floating Vanity With Blum LEGRABOX Drawers in 8 Steps for 35% More Bathroom Storage
A 900 mm floating vanity can add roughly 35 percent more usable storage than a standard footed cabinet of the same width. The gain comes from removing the toe-kick void and floor-contact frame, then building around a rated wall cleat, Blum LEGRABOX runners, and a splash-resistant finish schedule.
The cleat comes before the drawer hardware
A floating vanity sends its dead load and live load into the wall, without floor contact sharing the burden. A 900 mm cabinet made from 18 mm plywood, loaded with two LEGRABOX drawers full of bottles and towels, can reach 60 to 80 kg in normal service. That load reaches the cleat as downward shear plus a rotating pull-out moment, since the weight sits forward of the wall plane. A deeper projection increases that moment.
Use a continuous timber cleat, 45 mm by 70 mm, fixed into studs with M8 structural screws at every stud crossing. With standard 600 mm stud spacing, a 900 mm cabinet catches two studs reliably and sometimes three. Hollow blockwork or plasterboard without backing needs a backing board let into the wall or chemical anchors such as the Fischer FIS V system.
The cabinet hooks over the cleat with a matching bevelled rail. That French-cleat arrangement tightens under load. If the bevelled geometry is omitted, the screws carry the rotating moment in tension, the failure mode that drops wall-hung vanities.
Eight steps in a workable order
The sequence assumes a carcass already cut to size, with a 600 mm internal height and 500 mm depth, sized for a Blum LEGRABOX N-height drawer system.
- Locate and mark the studs, then fix the wall cleat dead level with a 1200 mm spirit level. A 2 mm error at this point multiplies across the cabinet face.
- Cut the matching 45 degree bevel into the carcass back rail so it seats over the cleat.
- Dry-hang the empty carcass and check the front face for plumb. Shim the cleat if the cabinet leans.
- Drill the LEGRABOX runner mounting holes with the Blum drilling jig, which sets the 37 mm system dimension automatically.
- Clip the runners to the cabinet sides, front fixing first, then the rear locator.
- Mount the drawer fronts and engage the TIP-ON or BLUMOTION mechanism according to the ordered specification.
- Adjust the four-way front alignment on each drawer with the side cams, top wheels, and tilt screws until the reveal reads an even 3 mm all round.
- Seal the top and any exposed end grain before the basin and tap go in, because access disappears afterward.
Step 4 is the common drift point. The LEGRABOX system allows very little side-clearance error: Blum specifies a 12.5 mm gap per side for the standard runner, so a 900 mm cabinet needs an internal width equal to the drawer nominal plus 25 mm. A carcass cut 1 mm narrow makes the drawer bind. A carcass cut 2 mm wide leaves a front that sags beyond cam correction.
Runner choice depends heavily on depth
LEGRABOX drawers use Blum concealed full-extension runners with integrated soft-close. The N-height profile is 66.5 mm, the C-height profile is 177 mm, and the standard dynamic load rating is 40 kg per drawer for the 40 kg runner, with 70 kg available for the heavy-duty version. For a bathroom vanity holding hairdryers, cleaning bottles, and folded towels, the 40 kg rating clears the real load with margin. Once the load class is settled, runner depth becomes the limiting selection.
LEGRABOX runners come in fixed lengths: 270, 300, 350, 400, 450, 500, 550, and 600 mm. The internal cabinet depth must exceed the runner length by the back-panel allowance, roughly 15 mm. Put a 500 mm runner into a 500 mm internal cabinet and the drawer box fouls the back.
Most floating vanities use the 450 mm runner in a 500 mm carcass. That leaves a rear void for plumbing, giving the basin waste and bottle trap space to pass. A notched drawer back lets the trap pass while preserving most of the drawer volume.
The front adjustment is a real advantage on a wide vanity. Each LEGRABOX front clips on and adjusts in four directions with the supplied key: height plus or minus 2 mm at the side cams, side plus or minus 1.5 mm, tilt at the rear, and depth at the front clip. Two 900 mm drawer fronts show tiny errors as wedge-shaped shadow lines, so the 3 mm reveal target gives the finished cabinet its built-in look.
Storage gain, expressed in litres
Compare two 900 mm wide, 500 mm deep vanities at 600 mm height. The footed version loses a 100 mm toe kick and a 100 mm top drawer rail to the door-and-shelf layout. That leaves about 400 mm of usable vertical space behind a single door, with a fixed shelf reducing practical reach.
The floating LEGRABOX version runs two drawers through the full height: one C-height front at 177 mm visible, with one tall front below. Usable drawer volume comes to about 0.9 by 0.45 by 0.45 metres of accessible space split across two trays, close to 180 litres of organised pull-out storage. The door cabinet offers a similar gross volume, yet only 110 to 120 litres of genuinely reachable space, because the rear third behind a door remains dark and awkward. The 35 percent figure in the headline tracks that reachable-volume gap. Drawers convert dead rear space into front-loaded access, which is the reason for choosing this layout.
Finish the timber before water reaches it
End grain is the weak point on a bathroom cabinet. Water wicks into exposed plywood edges, and the veneer lifts within a season. Seal every cut edge before assembly, especially the basin cutout.
For a natural wood finish, two coats of a hardwax oil such as Osmo Polyx 3062 create a matte, repairable surface that handles occasional splash. In heavy-use family bathrooms, a two-part polyurethane lacquer outperforms oil on standing water, with less convenient spot repair. The trade is repairability against waterproofing.
Stone needs separate treatment where the vanity meets a stone top or slate shelf. Lithofin MN Stain-Stop or the Fleckstop range penetrates porous slate and limestone without leaving a film, preserving the natural matte look while blocking oils and dyes that stain. Apply the sealer to clean, bone-dry stone and wipe off the excess inside ten minutes. Leftover sealer dries to a haze that needs solvent to lift. A second coat belongs only on areas where the first coat soaks in fast, which shows the porous patches the first coat missed.
Hiding the joinery
A floating vanity looks best with clean carcass faces and hidden fixings. Domino loose-tenon joints or 8 mm dowels with concealed glue blocks keep the corners tidy, and the LEGRABOX gallery rail hides the drawer-box screws inside the box.
The result reads as a solid block with two fronts and very little visual hardware.
Where plumbing changes the storage maths
The storage gain is real and measurable, provided the wall carries the load and the plumbing fits inside the rear void. A solid masonry wall with a chased waste pipe makes the build straightforward. A timber stud wall with the waste running through the same cavity as the cleat fixings forces one of three compromises: the drawer depth shrinks to clear the pipe, the pipe reroutes, or the cleat moves to dodge the stack. Finished-photo comparisons of drawer volume rarely show that conflict.
A finished vanity can hide the service route completely. The detail left unresolved until the wall is opened is the route of the waste pipe through the rear void.
