Cross-bracing a raised bed

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Old 05-03-17, 06:47 AM
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Cross-bracing a raised bed

I'd built two 5x10' raised beds, three 2x8" high (21.75"). On each of the 10' sides I spaced two 2x4's vertically on the inside of the bed. When I put it all in place I hammered 4' sections of rebar into the ground midway on the outside of each 10' wall.

They're partly filled with soil now, but I'm concerned I didn't cross-brace it enough.

I had two thoughts to fix this: run two 2x4's across the bed, connected to the center of each of those vertical 2x4s attached to the inside of the bed. Obviously I'd have to do some excavation. I'm concerned with how to attach those cross-braces to the vertical 2x4s--how to attach them so they don't pull free (would toeing them in be enough?), and whether the vertical 2x4s might themselves pull away from the bed walls.

Then I had a thought. What if I attached additional 2x4's midway along the 10' length on the OUTSIDE of the bed, and used 1/2" threaded rod, and drilled through both external 2x4 and the bed side and ran the rod across? I'd use heavy washers and nuts to hold them in place.
 
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Old 05-03-17, 08:35 AM
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So I would think a 21" high box, made with 2x8's filled with dirt will probably bow out some.

2x4's vertical are not going to give you much support.

I would have used 4x4's (min, maybe 4x6) in the corners with another along the 10' length.

For good measure a cross support between the middle 4x4 lag bolted to the post would be pretty solid.
 
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Old 05-03-17, 09:46 AM
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Thanks. Would it be overkill to put a 4x4 on both sides of the one wall (inside and out), bolt them together through the box, then bolt the cross brace to the side of the inner 4x4? Or would a vertical 4x4 on the inside (with the cross brace bolted to its side) be enough?
 
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Old 05-03-17, 09:47 AM
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If you are concerned about your side walls bowing out I would go with your threaded rod idea or an even simpler version. I'd just run the threaded rod across and not bother with another 2x4 on the outside though adding a 2x4 to the outside wouldn't hurt. Whichever you do I would make sure to cut off the excess rod flush and grind/file down any rough edges. Sticking out like that the threaded rod or nut is in a perfect spot to take a bite out of your leg. You can also goop on a good coating of silicone caulk to soften it up a bit and provide some cushion.
 
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Old 05-03-17, 02:16 PM
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Well, I went out and did it.

Went with the 6' threaded rod, 5/8" thick. But I used 4x4s on the outside: I cut a 4x4x8 into approximately 4 pieces (with a bit left over), placed two vertically in the middle of the 10' length, opposite each other.

I drilled through both the 4x4 and the sidewall (approx center of the 4x4 by length and width), and ran the rod through to the same on the other side. Put on big washers and nuts on either side and cranked it tight.

thanks for the feedback.
 
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