I am researching building a floor-to-ceiling book unit (about 140 linear feet) for my book collection. This was excerpted for a TOH short arricle and I surprised that ordinary pine hold more weight than plywood (3 feet) for the same amount of sagging.
1. Solid wood: Hardwoods make the strongest and stiffest shelves, but they are more costly than plywood or MDF. Softwoods are weaker and cost less than hardwood boards of the same size.
2. Hardwood plywood: These strong 4x8-foot sheets have minimal defects. Available in a wide range of face veneers suitable for paint or clear finishes.
3. MDF (medium-density fiberboard): The most affordable alternative. Not as stiff as solid wood or plywood, but won't cup, warp, or splinter. Takes paint beautifully. Use special MDF fasteners for best anchoring strength.
Strength Comparison: The amount of weight a 3-foot 1x12 shelf can hold without sagging more than ¼ inch:
Oak: 313 lb.
Pine: 200 lb.
Plywood: 129 lb.
MDF: 87 lb.
I have many books that are 13 x 10 (about 800 pages) or 11 x8 type (250-400 pages) so sagging is an issue.
Solid woods like oak, cherry, etc. are out-of-the question - - I was thinking about plywood veneer, but , as a first project, taking on buying wood from a specialty place, splinter-free cutting, finishing, etc, appear very intimating.
Thus, I was looking at plain plywood (trimmed w/ solid edges) etc., and paint finish (standard white). The paint could cover up knots, etc., and I wouldn't spend a lifetime of weekends on it.
But then, the article listed pine shelves as holding more weight than plywood ??