If you are not going to brace your work bench across the top, you will have to find another way to achieve the necessary stiffness and resistance to bending. Laminating two or even three layers of 3/4 (or 5/8) inch plywood would result in a work surface with adequate strength for your purpose, provided that you install legs at three foot intervals. The legs would have to be glue-lam assemblies, diagonally braced at the back. This avoids any obstruction along the front, and gives good access to the space under the bench.

Look down the list of topics for "Help me if you can, ASAP..." and see how to make a torsion box. Using 2x3 or 2x4 lumber and 1/2" plywood, you can achieve this 10' span without supports.

Thanks baymee, I will go check out the link.

Eric, we were planning to use postform Formica. The big boxes sell pre-made stock stuff pretty cheaply.

Knowing that three foot intervals is recommended distance for braces helps. I had better look up what glue-lam means.

Thanks

I have read the post. Thanks for that link. I am excited that we might finally have a solution to a storage problem that has caused us endless frustration.

Could you help me make sure I understand and get some more information on doing this.

I am assuming the tortion boxes going to lie 2' out and go 3' up, supporting a slab of formica postform vertically. Right?

One would go at each end--- then there would be extra supporting ones about about every 3' (The maximum span is 12'-- I just measured)I need about 17" plus wriggle room for each machine, so it would be nice if I could have the stalls 40' or so.

Is this a problem or is 3' truely a maximum?

Now about installing the support: The room is formerly a garage. It has tile floor (that broken type.. I can't think of what you call it, red shards of masonry laid on cement is what it looks like). The wall is brick kneewall 23" high coming out 4". Above that is old 1970s paneling nailed directly to studs. How do we attach these tortion boxes to the wall? (and floor????? I hope we don't have to attach it to the floor) We need the countertop's 24" depth measures out from the panelling, but it seems complicated to build the boxes with a cutout for the brick. We can put a furring strip screwed to the studs along the wall under the counter lengthwise. But I am not seeing how the whole thing would fit together.

Thank you again for any advice you can provide in this matter.

Amy

You've got things a little confused. The "torsion box" is a method of constructing a very strong but reasonably light deck/work surface. Picture a grid of sticks (the 2x3s or 2x4s baymee suggested) sanwiched between two plywood top and bottom skins, glued and well-fastened. That's a torsion box. It is so strong that it will allow you to span considerable distances with few vertical supports. "Torsion box" refers only to the horizontal part of this structure, not the supports it rests on. I would just glue a sheet of laminate directly to the top, rather than postform.

As to supporting this thing, I'd screw a ledger to the studs about 33" off the floor, keeping the ledger level, and let the torsion box sit on top of that.

I can devote more time to the answer later today, but if you build a torsion box as described, you can span 12' with, at most, one support in the center.

We have one in use now, built with 2x4's that is 4x8 feet surface area and it spans 8' with no support except on the ends and is stacked with heavy equipment. There is not a hint of deflection. Try going the full 12', load it up, and check for deflection. Then add the center support if necessary. I don't think any will be necessary. The important part is to secure it to the two sides that it rests on. It is not necessary to secure to the wall unless there is side to side movement.

For a table top of 24" wide and 12' long go about it like this:

Cut 24" wide strips of plywood; two @ 8' and the other two @ 4' long.

Buy some 2x4 studs, preferably 12' long. If using 8', get some straight studs, and dry. You don't have to overdo the straight part; the torsion box will straighten them out.

How ever you do it, attach the straightest 4' stud to one outside edge surface of the 8' length of plywood, using clamps and glue to pull the plywood close to the 2x4 before screwing it fast. I only use McFeeleys screws. Place screws about 8" apart. Now lay down the 4' plywood and join the two pieces of ply with an 8' length of stud. On the next row, and I would use 4 rows, alternate the 8' and 4' pieces so you don't have the ends of the studs at the same place. Do all 4 rows, screwed and glued to the 12' length of plywood. Now fill in the width of the plywood with blocks, screwed and glued between the long studs about every foot of length from end to end.

You are now ready to install the top sheet of plywood. Cover all the stud surfaces with glue and lay the 8' length of plywood over the section with the 4' plywood beneath it. Screw as before, every 8". Be sure to clamp the edges as much as possible. A cheap screw that is threaded the entire length will NOT pull two pieces of wood together withouat a clamp. McFeeley screws are unthreaded at the top for that purpose.

Allow to dry overnight and put into use. I would make the side supports the same way, but with 8" spacing on the upright studs. You can apply formica over the top of the plywood later on.

I hope you will let us know how the project went.

My husband says we really need to buy a pre-made countertop from Lowes or HD. We can get a 10' slab of 2' deep for under $90. Awfully easy. So making the torsion box top is out.

If we used that, would the torsion box supports still be the best support? It seems like a lot of work to make such a box, but it is always less work to do something right the first time than to do an easy option that fails, followed by four more easy options each failing

Lowe's claims that we could use the sturdiest shelf supports and space them at about 30" The person I spoke to said that should support 1000 lbs. But I trust "Lowes claims" about like I do "the government claims"
Also, we still have the problem of the 25" high brick wainscoatting (I don't know what you call this. Yesterday I called it a kneewall, but have learned that isn't right. Bacically the foundation of the home is brick. The former garage room has brick going up 25" from the floor. The entire brick is in the room, giving us a one brick depth ledge ) We couldn't put a shelf support over the brick on the panelling as it would make the counter too high. Rocklers sells shelf brackets 15-1/2'' Deep x 10-1/2'' High. Their tech help line says they would support 1000 pounds. Could I use these spacing them every other stud? It sure sounds easier than building boxes but......?????

Amy
Who is doing everything possible to make her husband's job easy so he he can spend his time doing more important woodworking --- like learning to make nice wooden sewing machine bases ; )

The torsion box would be a one-day project.

You could install shelf supports but they are only as strong as the screws holding it to the studs. I would space closer together, like 18" max.

You wouldn't need end supports as they would be held by the wall along the entire length.

"As to supporting this thing, I'd screw a ledger to the studs about 33" off the floor, keeping the ledger level, and let the torsion box sit on top of that."

If you use the torsion-box construction, you can incorporate the ledger as part of it. You would screw the 2X4 to the studs, then build up the torsion box with the rear 2X4 left out. Slip the TB over the ledger and fasten it. If you want to make the bench removable, you would not be able to use glue. The other question is whether you would want to put screws through a Formica top.

I have seen this method suggested for a "no visible means of support shelf".

Be very wary of using a pice of pre-fab counter without padequate support.
Most of these use particle board as the substrate and will sag if not fully supported (like they are when placed over base cabinets).