Torsion Box Shelving

[Keith Starosta]

The shelves in our walk-in pantry were originally constructued out of construction-grade particle board :rolleyes: , and have long needed to be replaced. They are sagging horribly under the weight of the pantry contents. After going over a few options with the LOML, I convinced her that it would look really nice if I were to build the new shelving in a "floating" torsion box style. I understand the concept behind the torsion box, but it's the actual construction that has me wondering. I'm figuring on using 1/4" (or maybe even 1/8") ply for the skins, hardwood for the outside edging, and hanging the shelves on cleats secured to the wall. My question is, what material is best suited for the webbing in this case? There will be two different sets of dimensioned shelves: ~5'x1'x1.5", and ~2'x2.5'x1.5".

I'd like to finish these shelves so they look like a nice built-in unit, so I'll probably go with a decent grade of oak ply.

Any thoughts would be greatly appreciated.

Regards,

Keith

[Jamie Buxton]

The spacer grid provides no stiffness to the structure. It just spaces the two skins apart, and that's where the stiffness comes from. This means you can use almost any material for it -- plywood on edge, solid lumber, whatever. I run the ribs the full length or width of the grid, and cut a sorta-half-lap joint at each crossing point. I say sorta-half-lap because it isn't a joint at all, but rather just notching for clearance. I strap the ribs together with that saran-wrap packaging stuff, and gang-cut the slots on the table saw.

[Dan Gill]

Making torsion boxes seems like a lot of work to accomplish what you need. Your longest span is 5 feet x 1 foot deep, right? The others are 2 feet by 2 1/2 feet. I would just use 3/4 inch ply with a 1 1/5 inch hardwood front edge. For the long shelves, I'd also use a back edge the same size. If the shelves are fixed, you can just use a full length back cleat. That should be plenty strong enough unless you're stacking several anvils on the shelf. If you don't think that's strong enough, add another hardwood piece tacked and glued down the center of the shelf. The shorter shelves should only need the front edge.

[Jeff Sudmeier]

We built the shelves for my parents pantry the way that Dan describes. We just built a frame out of 3/4 material and then used 1/2 inch ply for the shelves. It worked great!

[Wes Bischel]

Keith,

This should help:
http://www.woodbin.com/calcs/sagulator.htm

I used it for a TV shelf I built a while back - hasn't moved a bit! (though it would have dropped the TV on the floor if I had built it as planned:o )

Wes

[John Hemenway]

Keith, you say ""floating" torsion box style". By this do you mean the shelves are only attached by a cleat at the back and have no support at the front? If I am reading this correctly, these floating shelves can not support much weight. They are 'decorator' shelves.

I have seen some square-sectioned metal ell brackets that fit inside the torsion box of the shelf that would increase capacity but I would still worry about the ability of a floating shelf to carry the weight a pantry shelf loaded with canned goods. Either front supports or triangular brackets would be best.