Guide
How far can a shelf span without sagging?
Maximum shelf spans for plywood and pine, with and without a front edge strip, under books.
| Shelf, 11 1/4″ deep | Paperbacks (25 lb/ft²) | Heavy books (40 lb/ft²) |
|---|---|---|
| 3/4″ plywood | 27 1/2″ | 23 1/2″ |
| 3/4″ plywood + 1×2 edge | 36 1/4″ | 31″ |
| 1×12 pine | 31 1/4″ | 26 3/4″ |
| 1×12 pine + 1×2 edge | 38 1/4″ | 32 3/4″ |
Numbers computed by the same engine that writes the plans. Typical values; your town and your materials may differ.
Questions
How much sag is too much?
Furniture makers aim for about 0.02″ of sag per foot of span. More than that is visible and keeps growing over time.
What stops a shelf sagging?
A deeper front edge. A 1×2 glued on the front of a plywood shelf roughly halves the sag.