I am building a built-in bookcase with a 48" shelf span and want to
make sure that I am designing the shelving system properly to support
the span with minimal deflection. The shelves need to hold heavy
- The sides and back of the bookcase are 3/4" cabinet-grade birch
- Plan is to create 48"x12"x1" shelves by gluing together two sheets of
1/2" birch plywood.
- Shelves will be held in-place by a pair of 1/4" shelf pins at each
end. I plan to use sleeves to reinforce the shelf-pin holes.
I would like to avoid adding shelf-pins along the back because I don't
want visible holes. Also, I would prefer not to split the span since I
like the open look and don't want to have 2 narrow 2ft spans.
1. Is this construction strong enough to support a 4 ft span loaded
(I have had 3 foot span bookcases constructed from 3/4" material
and they seemed to hold)
2. Does anything else need to be done to stiffen the span? e.g.,
Thicker shelves? (I could use 3/4" to replace one or both of
the 1/2" pieces but then the shelves get heavier and
Torsion box construction? (I could sandwich a 1/2" layer
between two 1/4" layers but this is added work and
added opportunity to mess up :)
Shelf pins along middle of back wall? (I really would like to
avoid the visible line of holes down the middle)
3. Will the 1/4" shelf pins with sleeves be strong enough to hold the
load? (e.g., should I use stronger or more shelf pins?)
Also, do the sleeves do much to strengthen the holes or am I just
as well off without them?