shelvingwood
I'm installing shelving in my 5×5 kitchen pantry. My plan is to run 1×2 strapping on the back edge and left/right sides of each shelf, then use 1×12 boards as shelves. I'm considering poplar for the shelving materials.
I'm wondering if the side/back support will be sufficient or if I'll need a brace in the middle. We don't plan on putting too much weight on the shelves but I'd rather do the project once than have to come back to it later.
I'd use plywood with a thicker piece of hardwood glued onto the front edge. This gives you very good strength. Here is an online calculator I use to find what kind of materials you can use and the amount of sag you will have. Here's a good quote from the author of the site.
“The eye will notice a deflection of 1/32″ per running foot.”
55 inches is a rather long span for a 12 inch wide shelf that is supported on the ends and back side by the wall. One way that you could provide some more support for the shelves would be to add some center front supports for the shelves working up from the floor to the top shelf.
Best Answer
Unsupported 1x12 over a 5' span will sag (even under its own weight). As an alternative you could get some of these shelf tracks (~$2.25/track)
and some 12" brackets (~$1.30/brace)
and then lay your 1x12's on top to make the shelves. This option also allows you to easily adjust the shelves up and down, to suit your needs.
If you want to make the shelves completely from wood (as you suggest), you'll need to beef up the design and add additional supports.