Hi,

Putting this here because it is about building something new, though it isn't a home structure, per se.

I'd never consider using 2x3 or 2x4 lumber as joists. I get that it will not have the strength of other larger pieces, and deflection will be unacceptable. However, for an application where mass must be supported, but there will be no walking type dynamic load, and the distance is less than four feet, how can I best determine the appropriate lumber?

Long story short, ~200 lb static load that is around 48x40". Supported on the two edges, 48" apart. Think granite tabletop peninsula. So there needs to be a frame to prevent sag, but no run will be that long.

My intent is to use a ledger board on one end, put 3/4" plywood across the top, and then use 2x3 or 2x4 on the two sides and one in the middle underneath, tied into the ledger board and on the other end, the two supporting legs. They would of course be installed "vertically" so that the long edge was vertical and able to support better.

It seems to me that this would be a pretty strong frame with the mass adequately supported. The thing is, since it will serve as a table, the height from the floor to the bottom of the support is important, since were all pretty tall. So 2x3s on the outer runs, even in there is a 2x4 down the center, would be desirable.

But it seems like 2x3s are only to be used to cheap out on non-structural, non load bearing walls and stuff like that... Since this sort of is structural, but in a completely different sense, am I wrong in thinking that I might use 2x3s to build this table frame? Or must I use 2x4s given the 200 lb mass?

Thanks!

This post was edited by JHZR2 on Mon, Oct 13, 14 at 14:36