Under-Loft-Bed Tall Bookcase

Build the companion loft bed first, but leave out the bottom leg support on the side where this bookcase will be installed — the bookcase takes over that structural job. This bookcase is sized for a twin loft bed; for a full-size bed, cut every shelf and trim piece to 51" instead of 36".

Use the 1x12 sides and shelves to build the box. Mark your joints on both sides of every joint so you know exactly where to line boards up and where to screw. If using a pocket hole jig, drill pocket holes on the undersides of the shelves and attach to the sides; otherwise use 2" wood screws and glue. The back panel and shelf trim, added later, will help hold everything square.

Attach the footer to the bottom of the case. With a pocket hole jig, drill pocket holes in the ends of the 1x3 and attach to the sides; otherwise use screws and glue the same way as the box.

Cut the plywood back to fit and attach with glue and brad nails, catching every shelf.

Attach the top shelf trim the same way as the footer, with glue and 2" screws.

If the top two shelves will see real weight, cut scrap 1x2 pieces and fasten them to the sides just under those shelves — they're attached through end grain rather than the back panel like the bottom shelf, so this support adds real strength for the cost of material you already have leftover from the trim cuts.

Screw the bookcase to the sides of the loft bed's legs to stiffen the bed — the bookcase replaces the missing bottom support and is what keeps those legs square.

Sand every surface smooth and finish to match the loft bed.