Pictures please?

Here is an example of a book case in one of the bays with my couch in front of it

Here is a bunch of the bays lined up mostly painted

As you can see the angles makes it a little different than a normal closet.
The sides are 3/8 plywood with really nothing in between them.
The upper angle on the roof sheeting is some kind of plywood. But the lower angle is crappy sheet rock that you can't depend on for studs behind it.

It's no wonder the shelves sagged,they are over loaded. If you intend stuffing them like the picture,go industrial all the way. Seriously,the lower section with sheetrock needs to be overlayed with plywood and utilized for added support. Russian birch comes to mind for the intire project because exposed edges look good. 1x2 cleats on ends are plenty support for the shelves. To conceal end of cleats and stiffen shelves,glue 2" strips of plywood under and 3/4ths from front edge of shelf and to ends of cleats.

Those shelves with books are completely overloaded and sag because they are far too insubstantial.

Research torsion box shelf construction. You can make torsion box shelves and slide them in place on those supports you had under the original shelves.

At 44" they definitely need a support in the center, IMHO. Unless they are made stiff enough by other means.

Thanks for the replies.
I really don't want to replace the sheet rock with plywood. There are like 16 of these things in my house and that would really add to the project.

How can I do a center brace in this situation? I don't understand how I would attach it to the sides.

So would I just use thicker plywood for the shelf material. Recommendations?

Keep in mind I am just a homeowner trying to do basic projects, not a woodworker.

You might consider an extra shelf where you have the books between the top & bottom 1. That's a real overload & with extra shelf easier to get book out & less sag from less weight. It is hard to tell how long the shelves are, sofa pic it looks like 5-6 ft long, other pic looks. more like 4 ft. 6 ft is about max without center support I think. Could put 3 in. solid wood support up center & attach centers of each shelf & screw into the top wall, don't know exactly how to tell you but maybe someone could draw a pic of what it would look like.

Just throwing out another option to avoid center bracing. The attached picture shows how I built shelves for my closet. They are 8 feet long, holding up the full length of clothes plus whatever we have stacked on top with no noticeable sag. Adding material in the vertical direction stiffens the shelf up quite a bit. You can of course change the materials and sizes to what you need. Since you don't have a vertical wall to support the back edge of the shelf, you could build it with two stiffeners instead, one near the back edge and the other closer to the forward edge. If you're worried about the screws being visible on top, drive them a little deep, fill with drywall mud, and paint over it.

This post was edited by mosquitogang201 on Sat, Aug 23, 14 at 15:04

Thanks for the reply and drawing.

So simply attaching a board across the shelf will provide stiffness despite it essentially only being attached to the shelf. I can do that.

So simply attaching a board across the shelf will provide stiffness despite it essentially only being attached to the shelf?

Yes it will and that's the sort of basic fundamentals one should understand before wading into complicated projects. To start a large or unusual project without having built a few bird houses and whirlly-gigs is inviting failure. People spend years aquiring expertise. Why would a novice believe it possible to by-pass all the baby steps by asking an experienced individual to tell them all they need to know in 25 words or less? Ok,here's bracing 101. Cut 2 pieces of Baltic Birch Plywood 12"x2". Break one (or attempt to) with your hands applying pressure from edge to edge. Now do the same while applying pressure from side to side. Bracing 102. Stand a 2x4 on edge and step on it while noteing how much it bends. Fiip the board on it's side and step on it again. Which position did board flex least? Next we will see which drives nails best,4 little tap tap taps or a single athortive whack.