# Bench length without sagging



## Manitario (Jul 4, 2010)

Hey all, 
I'm building a bench out of a slab of elm to compliment a elm slab trestle table I've made for the dining room. The slab is ~2 1/2" thick and about 75" long. I'm just curious if it would be strong enough to support 4 people without bowing in the middle or if I'll have to design some sort of support for the middle of the span. 
In general, is there any sort of guidelines/calculator as to how long you can make a bench span before the weight of people sitting on it will bow it?
thanks!


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## Dusty56 (Apr 20, 2008)

How far in from the ends do you plan on placing the legs ?
If they're going to be at the very ends , I would put a support in the middle just to ease the stress on the ends and for stability. JMO : )


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## Manitario (Jul 4, 2010)

I was planning on putting the legs within about 6" of the ends…also considering making two shorter benches instead of one long bench…


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## Dusty56 (Apr 20, 2008)

I think the two benches would be better in the long run : )


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## DKV (Jul 18, 2011)

Rob, try the below. It's for shelves but aren't benches nothing more than shelves for people? Lot's of people use the sagulator. 2 or 3 inch edges run along the length of the bench also help with load.

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


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## Manitario (Jul 4, 2010)

you're probably right…just twice the amount of work!


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## DKV (Jul 18, 2011)

More methods…

http://www.diyadvice.com/diy/built-ins/materials-and-hardware/sagless-spans/


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## Dusty56 (Apr 20, 2008)

I'm just thinking about creature comforts…say you have a couple of children and a couple of adults seated. The kids would need to sit closer to the table than the adults which might make for some uncomfortable dining : )


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## Manitario (Jul 4, 2010)

Thanks DKV; that is exactly what I was looking for. Interestingly, the sag is quite a bit less than I expected, even with a presumed 200lb load/foot the sag in the center is only 0.1". Dusty, your point is well taken though, a bench with 4 people on it is inconvenient at best, although rather convenient for me to make…


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## Dusty56 (Apr 20, 2008)

What's four more legs in the scheme of things ? LOL 
I wasn't really concerned with the sag factor as much as I was with the future enjoyment of your projects.

I used to have as my signature ; "Do what you want to do , you're going to anyway" : )


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