I am in the process of building a roughly 12' x 16' shed/workshop. It is going to be a pier-and-beam design. There are 8 concrete piers, 4 on each side, that will support 2 4×12 beams. The span from the outside of one of the beams to the outside of the other is roughly 12'.
One possibility for joist/subfloor design:
- 2×10 doug fir joists, 16" oc
- One blocking sequence down roughly the middle
- 3/4 inch plywood
- Some form of construction adhesive between joists and plywood
- Screwing and/or nailing plywood to joists.
I think it's a fairly sound design overall, but I'm not sure how much "give" there will be in the floor after completion. Do you think that would have a lot of bounce, or should that be plenty?
According to the IRC, both southern pine and doug-fir-larch should be able to span 12 ft for 40psf live load and 20 psf dead load at 16" oc. See: https://codes.iccsafe.org/content/IRC2015/chapter-5-floors?site_type=public .
Will this be sufficient to have a floor without significant bounce?
Best Answer
I recently build a 8x14 shed using 2x8 pressure treated joists and there was no bounce. It felt solid with a 3/4" PT plywood floor. Your design is larger, so I agree with the 2x10 that you spec'ed. I don't think you'll have an issue it all.
I was originally going to try and save some money so I mocked up a few combinations of 16" oc and 24" oc with 3/4" and 1/2" plywood since it was "just a shed". The joists 16" oc with 3/4" ply was the only combo that felt solid (as expected). The shed had a small 4' "porch". For that I did use 24" oc joists with 5/4" PT deck boards. That was a stretch that I wouldn't have made for a full on deck, but it was fine for the small porch that would only have a few people on it with no static load.
I had 6 piers, so your 8 sound good. The only thing I second guessed is the depth of my piers. I was digging alone, and manually so I didn't get them as deep as they should have been. I didn't notice a problem, but I would suggest getting the recommend depth in your area for sure.