Shelf Width

[Luckbox72]

I am planning on building some bookshelves. The area I want to put it is about 45” wide. My question is just how wide can make the shelves before they will begin to sage under weight. I was thinking of making the shelves out of ¾” plywood with a solid wood banding on the front. I figured that would make for some strong yet good looking shelves. Should I make a center support or will that be strong enough to hold that large of a span.

 

[skysharks]

I would think that at least 24" would be good and you could probably go a bit wider. You would have to think how much deflect you would get when you loaded up the shelf with books over 24".
You could do a simple test. put a piece of shelving material on top of some type of support (2 coffee cans for example). SPace the cans 24" apart, measure down from bottom of shelf. Load up shelf with heavy books, then remeasure. If no difference push the cans out further till you get say 1/16" difference.
Then I would go back in from that point at least 6 - 8", just to be on the safe side,in case over time the weight could start a sag.

HTH

MAC

 

[Joe Scharle]

Start with the sagulator here:

http://www.woodbin.com/calcs/sagulator.htm

My personal experience has been a span of up to 30", with an edge band of hardwood glued on both edges.

 

[Mike Davis]

I made two sets of pine 48 inch wide book shelves 20 something years ago and they are packed full of books. They may be sagging a little now but no big deal. Screw a 1/4 inch plywood backing to the shelves and they will be fine.

 

[Glennbear]

I would think that at least 24" would be good and you could probably go a bit wider. You would have to think how much deflect you would get when you loaded up the shelf with books over 24".
You could do a simple test. put a piece of shelving material on top of some type of support (2 coffee cans for example). SPace the cans 24" apart, measure down from bottom of shelf. Load up shelf with heavy books, then remeasure. If no difference push the cans out further till you get say 1/16" difference.
Then I would go back in from that point at least 6 - 8", just to be on the safe side,in case over time the weight could start a sag.

HTH

MAC

Start with the sagulator here:

http://www.woodbin.com/calcs/sagulator.htm

My personal experience has been a span of up to 30", with an edge band of hardwood glued on both edges.

I made two sets of pine 48 inch wide book shelves 20 something years ago and they are packed full of books. They may be sagging a little now but no big deal. Screw a 1/4 inch plywood backing to the shelves and they will be fine.

Lots of sage wisdom here :icon_thum the idea of using "real world" testing is one I had not thought of before. I have used the sagulator and I have a bookcase constructed similar to the one Mike describes and after many years it is sagging but not intolerably so. :wsmile:

 

[gritz]

As a commercial contractor, I built tons of these over the years for legal libraries. I had an engineer compute the maximum span for adjustable shelves. His figure was 30" (with a 3/4 x 1 1/4" vertical nosing) for 3/4" 7 ply Birch plywood.

 

[Luckbox72]

Thanks for the input, but I think it might just be safer to add the extra suppport.
Now one more quick question. Should I build two units and join them side by side and put them on a single base, or would it be just as good if I was to build one unit with a center support, or One unit and have a strip than runs down the middle just on the front that could have shelf pin holes drilled in it and just simply add an extra pin or two for the front on the shelf.

 

[Mike Davis]

The big units I have are a pain to move, but not impossible. I have had to move them three or four times since I built them. Two smaller units will be easier to move if that looks to be in your future. The bigger unit will cost less to build. So, that's up to you.

The strip in front sounds like a good way to go.

 

[Mt. Gomer]

Thanks for the input, but I think it might just be safer to add the extra suppport.
Now one more quick question. Should I build two units and join them side by side and put them on a single base, or would it be just as good if I was to build one unit with a center support, or One unit and have a strip than runs down the middle just on the front that could have shelf pin holes drilled in it and just simply add an extra pin or two for the front on the shelf.

Two units side by side with a single base and face frame would give you more flexibility with your adjustable shelves....