I've also discussed a simple design for an open-frame free-standing bookcase using these shelves. Over the past 20 years, I've built many bookcases and workbenches this way, and none has any visible sag. Of course, your mileage may vary....
The short wood fibers (sawdust, wood chips, sawmill shavings) used in making particle board (AKA chipboard, fiberboard, pressed board) make it notoriously fond of sagging. Our trick is use of a long and relatively large dado -- a rectangular slot that allows a rear 2X4 support to prevent the particle board shelf from deforming.
Step 1: Materials and Tools
- A roughly 4' long slab of 3/4" thick raw particle board (shelving blank) 10"-12" deep
- The same length of 2X4 lumber (which is typically really 1 1/2" by 3 1/2"); hand pick a nice piece of construction-grade material
- Wood glue
- Flat black latex wall paint (easiest to find around Halloween)
- Wood stain and/or polyurethane in the color of your choice
- Router table/fence with 3/4" straight bit or a table saw
- Sandpaper or power sander
- Brushes for painting and staining