Plywood shelves - Will they sag over ~38" Span -- Items to be on shelves are clothing

[Robert Engel]

I think you get the idea....

....if you're still there, that is.

[Jim Dwight]

Sagulator says that 3/4 fir plywood, 38 inches long, 12 inches wide will sag 0.04 inches with a load of 10 lbs per foot. That is my conservative estimate for clothing. I don't think 0.04 inches is much. It's less than 1/16. I don't think it needs edging. If the load is heavier, maybe.

[Leo Graywacz]

Over time it will sag more.

[paul cottingham]

Groove the plywood. Route a tounge on the wood you are using as a stiffener. Roundover top and bittom, if you like that look. I doubt the resulting shelf will ever, ever sag.

[Mike Henderson]

I had a similar problem. I have a couple of closets that hold household items - heavy things like dishes. I bought some aluminum angle iron from Home Depot and put it on the front and back of the shelves.

You can barely see the angle iron on the front of the shelf in the picture. It's the same in back. The "angle" part goes under the shelf. Anyway, no sagging.

Hall closets 002.jpg

If I recall, the shelves are 3/4" Baltic birch.

Mike

[Allan Speers]

Over time it will sag more.

This. Believe me, I know for sure!

- I'm never going to use plywood for shelves again.

[Phil Thien]

I've never experienced plywood sagging more over time.

MDF and particle board yes. Plywood, no.

[Bill Neely]

Yes, they will sag. They make metal T stiffeners that you can route into the front and rear edges to span that distance then cover with edge banding or you can go with thicker shelves, or add solid edges. Depending on the depth you could use 1/2" plywood backs and add pins or magic wire at the mid span, or hang the shelves on z clips which will minimize sag at the front by fully supporting the rear. But with no support mid span I predict sag.

Peter, Can you be more specific about the edge stiffeners, I'd like to take a look at them.

Thanks

[Allan Speers]

Peter, Can you be more specific about the edge stiffeners, I'd like to take a look at them.

Thanks

I made a bunch of 48" plywood shelves, and as they were getting lower and lower each month, I finally took them down, routed the front edges, and glued-in 1" steel L-channel. This, combined with the backs being glued in place, keeps them nice and level. - but it sure cost a lot.

Next time I'll use Oak, or at least Pine. ANYTHING but plywood.