How far can plywood span unsupported?

[Rootus]

I'm building three workbenches, following specs:

36" 2x4 legs
3 shelves (including top) framed this way:
96" 2x4 spans w/36" 2x4 center support leg
24" 2x4 rails (actual rails are cut shorter, overall depth is 24" however)

Everything is screwed together using Simpson RTC24 brackets (KWB1 kits). Overall dimensions are 96x24. The two lower shelves will be regular 3/4" plywood, the top will either be plywood, or if I decide I want to fork over another $500, Ikea butcher block. Still waffling a bit on that decision.

My question: What kind of support would 3/4" plywood need in addition to the basic 96x24 frame? I'm not going to be loading absurdly heavy things onto the shelves, mostly just power tools & such. And same question for the top, if I go with the 1.5" butcher block -- what kind of extra supports should I use for it?

 

[Toolfool]

You should be fine. 2 x 4 on edge, spanning less than 4' is plenty stout. And if you opt for the butcher block, you could drive on that bench. I would put a couple of 2 x 4 x 24" spreaders in as well (build like a ladder).

 

[Walty]

I always build my benches like walls. Frame around outside and studs 16-24" o.c. to support the middle of the bench. Never had a problem. Overkill? Ya-probably, but like I said, never had a problem.

 

[NUTTSGT]

16" centers will add about $8 bucks to your project....
Throw the $8 at it.

I was going to say that over building that bench wouldn't more than an extra ten bucks. Over build it and be done with it.