Rule of thumb on table bench design

Hi All, Im in the process of designing a kitchen table, nothing exciting, sort of transitional modern, clean lines, etc. 1" top, 2" aprons, mitered 2" square legs. Anyway, the Boss is hoping for a sort of mini-table as a matching bench. The dimensions for the table top are 36"x60", so nothing crazy there either. The question I have for you guys is what kind of weight would a bench be able to support with those dimensions? At 60" long I would expect the bench to frequently hold two adults, and infrequently 3 adults. Is a 2" stretcher under a 1" benchtop supported by 2" square legs enough overall support? I'm sorta thinking no. Id be worried about bow in the bench and stress on the legs, but Ive not built a bench before, not like this anyway. Is there a rule of thumb when it comes to dimensioning-out a bench? I could easily sneak a third middle set of legs in there and keep the design cohesive. Not so much with a lower stretcher. At the moment the design is using all walnut, but I could limit the top to walnut and the supporting pieces to something else if it mattered. Im working on the sketchup now, so Ill post that for a visual guide when its mostly respectable. Any input is appreciated!

Getting your ideas into SketchUp or even just sketched onto a pad of paper should help to visualize what you're trying to do. Basically, it just sounds like you're describing a card table--the kind with the fold-out legs that grandparents breakout for the kids when there's no more room left at the formal dining table. The typical card table has 1" tubular steel foldout legs attached to a steel framed top that's usually covered with masonite or hardboard. You wouldn't think they're very strong but I'm using one right now as a temporary workstation for my DeWalt miter/chop saw. That would be strong enough, I would think, for two or four sets of elbows.

To get the creative juices flowing, you could start on Google or Pinterest to get a bunch of images that appeal to your own thoughts on design. The New Yankee Workshop has an earlier video that you could also locate on their site (or on YouTube) showing how to build a Tap Room Table that's also close to what you're describing.

When I moved out my father made a trestle dining table for me about that size. He made a matching coffee table at chair height to use as extra seating. It's about 24" wide and made of 1 1/2" pine. It held a couple decent sized grown ups for dinner many times without a problem. By decent size I mean 200 pounders and not the Big Mac Super Sized ones that tilt cars when they get in. If you use an apron the top can be thinner. Mock one up with the wood on a couple saw horses and see how much it deflects when you sit on it.

Id be more concerned about the bench/ table racking. Maybe I'm not understanding since I don't know what 2&qout means.

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Originally Posted by Christopher Juncosa

Hi All, Im in the process of designing a kitchen table, nothing exciting, sort of transitional modern, clean lines, etc. 1" top, 2" aprons, mitered 2" square legs. Anyway, the Boss is hoping for a sort of mini-table as a matching bench. The dimensions for the table top are 36"x60", so nothing crazy there either. The question I have for you guys is what kind of weight would a bench be able to support with those dimensions? At 60" long I would expect the bench to frequently hold two adults, and infrequently 3 adults. Is a 2" stretcher under a 1" benchtop supported by 2" square legs enough overall support? I'm sorta thinking no. Id be worried about bow in the bench and stress on the legs, but Ive not built a bench before, not like this anyway. Is there a rule of thumb when it comes to dimensioning-out a bench? I could easily sneak a third middle set of legs in there and keep the design cohesive. Not so much with a lower stretcher. At the moment the design is using all walnut, but I could limit the top to walnut and the supporting pieces to something else if it mattered. Im working on the sketchup now, so Ill post that for a visual guide when its mostly respectable. Any input is appreciated!

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Your text is coming out garbled, see above. Are you using a word processor and pasting your post into the site form? I'm assuming the "1&quote; " thing is 1", etc.?

That aside, take a quick look at this page: Dining Table Design Basics 101. They recommend 23-30" width/person, I'd hate to be the adult in the middle of a 60" table. You won't get much resistance to racking with a 2" apron on the table and the same size apron on the 60" bench won't help carry any significant weight. I'd hate to think of three 200-lb adults loaded onto a 5' long 1x12. :eek:

Do a search on table and bench design standards, you can read for days. This wheel was invented thousands of years ago and refined over the years. A little homework goes a long way.

"Maybe I'm not understanding since I don't know what 2&qout means."

Didn't that used to be a Mac/PC formatting problem? Is that still a thing?

Maybe it is, I'm posting this from my iPad

test 1"x2"x3"

Edit: looks good on Firefox on the PC.

Ahh yeah it is all garbled. Im on a Mac so maybe thats the issue. Thanks for the replies nonetheless.

Test 1". Nope, looks good, dunno maybe the site had a hiccup.

Ill try and get the sketchup done. The bench will be 16" deep, 46" long, 18-20" high (not figured that out yet ... sketchup). The stretcher will probably be 1" thick. I guess my first concern was deflection, but racking could be a problem. Easy enough to beef up the base.

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That aside, take a quick look at this page: Dining Table Design Basics 101.

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Bill, looks like this link is dead but Ill definitely track down the document. That obviously seems like a great resource. Thanks for the input!

You're welcome. I fixed the link, sorry about that. I must not have checked it after I posted.

Christopher

I recommend that you use Sagulator to calculate how much deflection you can expect in your bench. I plugged in my understanding of the design that you described and got a result of about 1/8" total deflection from 600 lb distributed along the 60" bench. I'm not an engineer but I have studied this as well as I am able. Breaking calculations are intuitively what you want, but I can't use them. I assume that wood will flex a lot before it becomes permanently deformed (let alone, break) so 1/8" over 60" seems negligible to me.

I think Andrew Hughes' point about racking is also very important. If you use decent joinery (M&T, bridle, or half-lap) with 2" aprons I think that the joints on the table and the bench will resist racking very well. Moore & McKenna published a test of joinery in the Jan/Feb 2009 issue of Fine Woodworking. The half-lap joint was, surprisingly, the strongest, followed by bridle joint and thick (3/8") M&T. In 3/4" x 2 1/2" cherry the half lap broke from racking force at 1600 lb and the M&T broke at 1400 lb. (Suggest you read the article for details.) So, four joints would give you a breaking point of about 6000 lb. If your center stretcher under the top is joined to the short aprons, you might even get a bit more strength. If you are still not confident, add gussets inside each leg.

Doug

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Originally Posted by Doug Hepler

I recommend that you use Sagulator to calculate how much deflection you can expect in your bench.

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I think Andrew Hughes' point about racking is also very important. If you use decent joinery (M&T, bridle, or half-lap) with 2" aprons I think that the joints on the table and the bench will resist racking very well. Moore & McKenna published a test of joinery in the Jan/Feb 2009 issue of Fine Woodworking. The half-lap joint was, surprisingly, the strongest, followed by bridle joint and thick (3/8") M&T. In 3/4" x 2 1/2" cherry the half lap broke from racking force at 1600 lb and the M&T broke at 1400 lb. (Suggest you read the article for details.) So, four joints would give you a breaking point of about 6000 lb. If your center stretcher under the top is joined to the short aprons, you might even get a bit more strength. If you are still not confident, add gussets inside each leg.

Doug

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Doug, thanks very much for the resources! And the aptly named sagulator was really exactly what I was trying to wrap my head around and made me chuckle at the same time, so double thanks and that link has been bookmarked. Also very useful information about racking resistance of the different joints. I also wouldn't have thought the half-lap would do that well. Admittedly I haven't worked out the apron/leg joinery so this advice is timely as well. The table this will be for will probably use a 3-way miter at the leg/apron and I haven't decided if I'll do that on the bench as well. I might just to maintain the aesthetic parity with the table as well as get that many more attempts on a technique I haven't done before.

Thanks everyone!