that you're going to have stacked or otherwise situated on the shop floor. That's you, your workbench, tools, and wood stock/etc. For your case, with 24' spacing, you're probably going to be at least 20 psf (possibly 30-35 psf), depending upon the type of wood in the joists and the type/thickness of sheeting that you use to cover the floor, if you sheetrock the ceiling below, etc.
For either of the joist calculators referenced in the previous postings, some of the critical input are your selections of dead and live load, and you need to have both for a realistic estimate of your requirements.įor a 2 x 8 joist and a double layer of 3/4' something (plywood/osb a single layer will probably be too thin to support heavy equipment) you're looking at something on the order of 15 pounds per square foot (psf) minimum for joists at 16' centers. The previous two replies are correct- your 2圆's are too light to support anything but a short span if that span has any kind of load on it.
I thought I'd add to the discussion here, since my day job allows me to add 'PE' behind my name.