Floating shelves from one sheet of plywood: cut list and hidden bracket

A floating shelf looks like it has no support because the bracket is hidden inside it. Built as a hollow box, open at the back, a shelf slides over a cleat screwed to the wall and the cleat never shows. Two shelves, each 900 mm (about 35.4 in) long, 220 mm (about 8.7 in) deep and 54 mm (about 2.125 in) thick once finished, come from a single 18 mm plywood sheet with enough left over for the two wall cleats as well. The full parts list, the kerf math for how it all nests, and how the hidden bracket works are below.

Building the shelf as a box instead of a solid plank does two things: it keeps the weight down for a long shelf, and it gives the inside a cavity for the cleat to sit in, so no bracket, screw, or batten is ever visible once the shelf is on the wall.

How the hollow box and hidden bracket work

Each shelf is a shallow box: a top skin and a bottom skin sandwich a three-sided frame made of a front lip and two end pieces, with the back left completely open. The frame pieces are 18 mm tall, so once the skins are glued on top and bottom the box has an 18 mm tall cavity running the full width of the open back, just behind the front lip.

The cleat, a plain strip of plywood screwed flat to the wall across two or more studs, is ripped narrower than that cavity, about 16 mm (about 0.6 in), so the box slides over it with clearance rather than binding. The shelf is pushed on until the front lip meets the wall, and the cleat's own length and the shelf's weight resting on top of it do the holding. A single screw driven up through the bottom skin into the underside of the cleat adds security without ever being visible, since it sits on the underside of the shelf facing the floor.

Parts list, two shelves

Each shelf uses two 900 × 220 mm skins as the top and bottom faces, one 900 mm front lip, and two end pieces. The end pieces run from behind the front lip to the open back, so their length is the shelf's 220 mm outer depth minus the front lip's 18 mm thickness: 220 − 18 = 202 mm (about 8 in). Each cleat is cut 700 mm (about 27.5 in) long, short of the shelf's full 900 mm length, so it sits comfortably inside the cavity without reaching either end.

How it all nests onto one sheet

Here is exactly how both shelves, all ten plywood parts, come from a single 2440 × 1220 mm (about 96 × 48 in) sheet of 18 mm plywood, using a 3 mm saw kerf.

• Rip the sheet across its 1220 mm width into two 220 mm strips for the skins, each the full 2440 mm length: 220 + 3 (kerf) + 220 + 3 (kerf) = 446 mm, leaving 1220 − 446 = 774 mm of width for everything else.
• From each 220 mm strip, crosscut two 900 mm skins: 900 + 3 (kerf) + 900 = 1803 mm, leaving a 2440 − 1803 = 637 mm offcut per strip. Two strips give all four skins needed.
• From the 774 mm zone, rip an 18 mm wide strip for the front lips, leaving 774 − 18 − 3 (kerf) = 753 mm of width. Crosscut both 900 mm lips from it: 900 + 3 (kerf) + 900 = 1803 mm, leaving a 637 mm offcut.
• From the remaining 753 mm, rip another 18 mm wide strip for the end pieces, leaving 753 − 18 − 3 (kerf) = 732 mm of width. Crosscut all four 202 mm end pieces from it: 4 × 202 + 3 × 3 (three kerfs) = 808 + 9 = 817 mm, leaving a 2440 − 817 = 1623 mm offcut.
• From the remaining 732 mm, rip a 16 mm wide strip for the two cleats, leaving 732 − 16 − 3 (kerf) = 713 mm of width spare. Crosscut both 700 mm cleats from it: 700 + 3 (kerf) + 700 = 1403 mm, leaving a 1037 mm offcut.

That is two complete shelves and both hidden cleats, ten parts, from one sheet, with a 713 × 2440 mm panel still untouched, plus several smaller offcuts, more than enough for a third shelf's end pieces and cleat, or a shelf pin strip for a cabinet elsewhere.

Sizing your own shelves

900 mm long and 220 mm deep suits a hallway or a run of box shelves above a desk. For a longer shelf, keep the 54 mm finished thickness and just lengthen the skins, front lip, and cleat together, the end pieces and the 202 mm depth maths do not change. For a deeper shelf, grow the skin depth and recalculate the end piece length as outer depth minus the front lip's 18 mm thickness, the same subtraction used above. A longer or deeper shelf also wants a longer cleat and more fixing points into studs, since the load it carries grows with its size.

The 18 mm cavity height comes directly from using 18 mm plywood for the frame pieces. Building the frame from a thinner off-cut, such as 12 mm, shrinks the cavity and the finished shelf's overall thickness to match, useful for a slimmer-looking shelf as long as the cleat is ripped to fit the smaller gap.

Fitting the hidden bracket

Find the studs behind the wall where the shelf will hang and mark their centers. Screw the cleat flat to the wall across at least two studs, checking it is level before driving the screws home, since any tilt in the cleat carries straight through to the shelf. Dry-fit the shelf box over the cleat before any glue goes on the frame joints, to confirm the cavity clears the cleat along its full length and the front lip sits flush to the wall with no gap.

Glue and pin the frame together first, front lip and both end pieces, check it for square, then glue the top and bottom skins on. Let the glue cure fully before loading the shelf, the skins are what carries the load across the open span, not the glue line alone while it is still green.

What to buy

One sheet of 18 mm plywood covers both shelves and both cleats. Add PVA wood glue for the frame and skin joints, panel pins or brads to hold the skins while the glue sets, and 38 mm (about 1.5 in) screws to fix each cleat into the wall studs. A tube of paintable filler covers the pin holes and any grain mismatch on the front lip and end pieces before painting or finishing.

Plan your own shelf cut list

Scale the length, depth, and frame height to match the shelves your own wall needs, the parts list and the nesting method above both scale with it.

SawReady works out the nesting and sheet count for any part list. Enter your shelves' dimensions, set your sheet size and kerf, and it returns the layout and the exact number of sheets to buy.

Plan my shelf cut list