I am putting plywood shelves in my closets that look something

>>931636
Forgot to add, the two longest shelves around around 7 and 9 ft respectively.

>>931637
That's a crazy span for 5/8 plywood. Should have used solid wood but... I would say you need to add a post or something in the middle to support the shelf. What kind of closet rod are you using? A wooden one will sag like crazy just like the shelf.

>>931647
I was going to use the tabard ~1 inch metal rod they sell at Lowes, but it only comes in 8 feet. So I might just buy some ~1 inch EMT conduit which comes in 10 ft sections.

To add, the shelves are about 13 inches deep.

I doubt I'd end up doing this, but what if I laminated a 1/4 inch piece of plywood to the bottom of the shelves? Would that do much of anything?

As help for potential future DIY anons, plywood is a bad choice here to begin with. If you can't do solid wood (the preference), oriented strand board (OSB) with a thick veneer is much more rigid.

To do what you're asking I guess you could take a small square of wood a couple inches tall, make a divot in the bottom that can rest on the rod, and then attach it to the middle of your shelves. Personally, I suppose you could attach a 1x1 under the front edge of your shelf. Sure it reduces head space, but it will also mean your shit won't spill off the shelves. That still might not be enough. Actually, 9' across. I've never made one that wide. A vertical support seems almost mandatory.

>>931659
Isn't plywood generally more dimensionally stable and stronger than solid wood of equal thickness?

>>931674
no. Plywood IS more dimensionally stable (doesn't shift in size with humidity), and is stronger ACROSS the grain than a similar board, but is weaker ALONG the grain than said board, and also much more prone to sagging over time. OSB and plywood behave essentially the exact same, but plywood isn't damaged by water as much, as OSB will swell unevenly.
I agree with >>931647, however you may also get by with using a face frame. you need to glue a board along the front of the plywood shelf, not just face nail it. you nail it after the glue to give some clamping force if you don't have anything better.
otherwise the nails will quickly work themselves out/cut through the soft pine as you load and unload the shelf, because they have enough give to build momentum. So pry out nails, add glue, and nail back, should help quite a bit. Other solutions that come to mind is >>931647 adding a post along the center of the shelf in the middle if it's sagging from front to back (instead of sagging from side to side).
Or adding a post/series of posts in the middle. If you go that route, I suggest a furring strip in front of the shelves in the middle, and one cut into pieces the length of which is the spacing between the shelves glued to the center. So building dados for the shelves by gluing up the two boards. This will work much better than just nailing a vertical board to the front of the shelves, because the boards will transfer all the weight down to the floor rather than relying on the nails to support them.


>>931636 Also, I approve of your instincts, but sadly are misplaced. You need to hang the closet rod so it cannot be attached rigidly to the shelf, or there would be no space for the hangars. Hopefully you have one thick enough that you won't need a support in the middle of the shelf.

>>931697
To clarify about the closet rod. I was going to hang it a few inches under the shelf as normal. What I was thinking of doing was drilling a hole into it and threading a ~3/8 threaded rod into it (perpendicular to the surface) and somehow attach it to the bottom of the shelf. That way it would support the front edge of the shelf.

Glue an upstand on the front edge flush with the top (30x50mm ish) which will add stiffness and make it look smarter.

>>931886
This but brad it as well as nail it. You can also glue/nail a batten widthways on edge on the underside of the middle of the shelf.

>>931915
Sorry I meant brad/nail as well as glue.

File: understanding-wood-supports-for-art-5.jpg (8KB, 290x189px) Image search: [Google]

8KB, 290x189px

>>931697
>along the grain
>across the grain

Solid wood board is more prone to sag as the wood fibers are only present in one direction, be it across the width or over the length. See pic for detail of plywood.

>osb will swell
Depends what grading you use. Structural OSB is water and moisture resistant to prevent this from happening. It is commonly used in place of tongue and groove floor boards.

>>931886
This would be a simple resolve given your current position.

>>931922
You don't have a clue what you're talking about. If all the grain in solid wood is running across a span how is using plywood and having almost half the grain running the wrong way any stronger? Have you ever actually framed a house? Do you know what OSB, even top of the line, looks like after spending a month or two in the rain. There's a reason good builders use plywood not OSB. What is Structural OSB, non-structural OSB doesn't exist, that's like saying "lumber wood" or "sheet plywood". All sub-floor materials are tongue and groove even OSB and plywood and floor boards? I think you mean shiplap which hasn't been used for house construction in almost 100 years.

Don't go around spewing bullshit and pretending you know what you're talking about.