How to repair bench cross members.

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Old 04-18-19, 05:37 PM
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How to repair bench cross members.

Hi. First-time poster here. I have a question on how to repair my mid-century modern bench. The upholstered bench sits on a steel beam attached to legs. Unfortunately, the wooden cross members inside the bench that attach to the steel beam have broken out. Obviously, the pine 2x6 could not handle the weight of a person sitting on top of the bench and the cross members broke out around each pocket screw. (see pictures)

So, what can I replace these broken cross-members with? Would hardwood be better? Perhaps pine would still be fine if I used an attachment method other than pocket screws? Maybe some sort of steel strap or angle brackets? It will have to resist the stress of several hundred lbs pressing down on the bench (and thus the cross member). What do you folks think?

Hopefully, these pictures will help illustrate the structural failure that has occurred.
 
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Old 04-18-19, 07:22 PM
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I don't think the pocket screws are the problem. Use oak and wood glue and pocket screws next time. Hard to tell from the pics but if the oak could possibly be thicker, that might help. The thicker the oak is, the farther back the pocket hole will be since the screw is supposed to exit the wood nearly in the center of the end grain. A tight fit plus glue AND screws will help.
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It's kind of a dumb design though. I don't know why the cross members aren't about 6" longer so that they go all the way across the width of the seat (where all the screw holes are in those rails.) That way the weight would be dispersed and wouldn't be on the pocket screws only.
 
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Old 04-19-19, 05:00 AM
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To fix the problem permanently I would not use wood cross members like that. I would put steel plates across the bottom of the frame then attach the leg to that. You could use wood but it would be more visible. Steel can be thin and painted black so you'd hardly notice. Judging by the screw holes in the side frame of the bench it looks like something similar might have been done at one point.

Right now all the load is being carried by the screws in sheer which is just asking to rip the wood apart like your photo. Worse is the twisting motion when weight is put on the edge of the bench and since the leg mounting bracket is small and in the center the bench provides leverage to rip the screws out.
 
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Old 04-19-19, 05:38 PM
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Thanks. I agree that it should have been glued for extra strength but the frame rails are actually stacked 3/4" stock instead of 1 1/2" and the edges are not well aligned so a good glue joint between the cross members and the stacked rails will be hard to achieve. I like Pilot Dane's idea of a metal plate but not sure where to get one.
 
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Old 04-19-19, 06:58 PM
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OK. I decided to take both of your pieces of advice:
  1. Better wood (still fir b/c I don't have 1.5" oak) without knots.
  2. Pocket holes drilled for appropriate stock width (last time looks like pocket holes were set for 3/4" stock so were too close to the edge) along with appropriate length screws.
  3. Wood glue.
  4. Steel plate fashioned out of leftover pro-grade garden bed edging (bendable over many feet but plenty rigid for a 13.5" plate). Plate will be over wood brace so that I still have something to screw thru.
I'll post pics when done. Thx for advice.
 
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Old 04-20-19, 04:07 AM
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Most home centers have a selection of steel and aluminum in flat bar and angles of various sizes. Some are even pre-punched with holes to easily make brackets. You can also find steel parts to reinforce the bench in the lumber section. Look in the joist hanger and hurricane strap area. There are flat plate and angle brackets of varying sizes that work great for reinforcing things.
 
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Old 04-23-19, 09:57 AM
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Thanks Guys. I finished up yesterday and the bench is rock solid now. I think that steel plate is going to provide great longevity.
 
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Old 04-23-19, 12:00 PM
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Yea... that's the way to do it. It should last a very long time.
 
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