plywood, weight capacity


How can I figure the amount of weight a piece of plywood, probably 3/4 or 1" ... how much weight it would hold? It would be 24" x 60" and supported on both 24" sides and one of the 60" sides? The weight would be evenly distributed but there wouldn't be any support in the center except along that one side. I could use butcher board or block, whatever it is. Thanks ...
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This may help http://www.woodbin.com/calcs/sagulator.htm
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for a shelf or platform that size.
Don Young
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Don Young wrote:

You must be using plywood made from cardboard. 3/4" plywood on 24" studs (essentially what the op is doing) is never going to sag by itself.
The Sagulator, shows that a 1400 pounds would result in a deflection of 0.1 inch. a sag of 0.1" wouldn't be a problem even if visual was important.
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George E. Cawthon wrote:

I don't think your reading the OP's specs. It is 24X60 shelf supported on both ends and along one of the 60" sides leaving one of the 60" sides unsupported it will deflect and sag under it's own weight with that configuration over time. Time to recalculate with the "sagulator".
Rich
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Rich wrote:

Sorry, I apparently read it wrong, thinking it was supported along the two long sides. Don't think the sagulator will help. It won't sag along the 24" sides or the one 60" side. 24 inches wide is pretty wide, so with enough weight it will sag. It will not sag on it's own from my experience.
I have 10" wide shelves 30" long supported only on the end and they don't sag with a full load of large books. I also have a bookcase with 9" wide shelves 48" long and supported with nails through 1/4" plywood on the back edge and these shelves don't sag with a full load of magazines. Each shelf supports 140 pounds (I weighed a 6" section of magazines).
The only way to tell how much the ?shelf? will sag is to support a 2 x 5 shelf on 2x4's (on the floor) and step on the shelf along the unsupported edge and in the middles of the long length (and on other parts of the shelf). That will give a decent idea of what the shelf will support. I suspect that the shelf will support at least 300 pounds distributed evenly over the shelf with little sagging.
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That's what it says for a 24" wide and 60" deep 3/4" shelf...
But a 60" wide x 24" shelf would initially sag 3.89" with a 1400 lb load.
Nick
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snipped-for-privacy@ece.villanova.edu wrote:

numbers are with both long sides unsupported. The sagulator doesn't calculate with one long edge supported. If you support one long edge, sag will be reduced a lot. Elsewhere I suggest that the shelf would likely support 300 pounds ok. , Deflection would likely be less than 1/4" at the center of the unsupported edge, but certainly no more than 1/2 inch.
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Certainly? :-)
Nick
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what the OP is posing is that he is building a shelf with two supports on either end and one in the back the length of the board. looks like this:
------------------------------------ | | | | | |
where the ----- side is 60" and the | sides are 24".
I made a 54"x20" shelf from 1/2" MDF for linens and such, and it doesn't sag at all because we supported the back with a furring strip 54" long.
Since you want a lot of weight on it, it's probably going to be utility use and appearance is second concern. I'd use OSB tongue and groove flooring (the yellow painted edge stuff) I think it's 3/4" thick. If you think about how that stuff mounts in homes on trusses and how much weight it holds without warping.
You could also use corrugated tin and roll the edge over in front if you're holding something like paint cans. ugly, but it won't deflect even if you jump on it.
good luck.
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snipped-for-privacy@ece.villanova.edu wrote:

equally distributed. 10 square feet, each foot would support 30 pounds. Place 30 pounds on each square foot that has a supported edge and you would not see any obvious sag. That leaves only 3 square feet in the middle of the unsupported edge. How much would one expect the thing to sag if you place 30 pounds on each of those square feet?
The whole thread is a bit silly. If weight carrying and shelf sagging were an issue, any reasonable person would simply face the unsupported long edge with a 3/4" x 1-1/2" piece or place the sheet atop 2x4's supported at the short ends.
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On Mon, 8 Jan 2007 16:15:36 -0800, "AKA gray asphalt"

You search on the keywords "plywood span table" and get something like this:
http://www.greatnorthernlumber.com/simpplyr2.html
Lots. I have to say, the arrangement you describe seems destined to sag on the loose edge, and dump whatever you're trying to hold up. You're probably better off fastening the crap out of the two ends, and leaving off the supports on the long side, so it can sag evenly. I doubt you'll be able to make the plywood fail in that configuration before whatever you're attaching it to comes loose.
What are you trying to do?
--Goedjn
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