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I'm going to make a swing as a project with my kids. I'm constrained by the timber available and wondering if doing the whole thing with 4 by 4's will be ok rather than a thicker top bar. Or if I could double up on the top bar?

Ten foot high and close to that wide is my plan so far, all legs concreted into the ground 50cm, but I want 2 swings on it, rather than just one.

Will an a-frame bolted together with 4 by 4's be safe? Would I need to double up the top bar?

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  • At that size a single 4x4 is a big accident waiting to happen, I would not be sure if doubled 4x4 will be enough with larger children.
    – Ed Beal
    Dec 1, 2018 at 17:09
  • I've built a 4x4 A-frame swing in the past, but I had 3 2x8s across the top, glued and bolted. 4x4s were buried into the ground, the thing never moved. It had 4 swings.
    – Gary Bak
    Dec 1, 2018 at 17:17
  • 2 by 4 and 4 by 4 are all that is available here, unless I buy a tree trunk, which is overly expensive. Any suggestions welcome. I contemplated a metal pole, but I don't have metal cutting or welding tools so that's no an option unless I get it precut. Then bolt holes etc would be an issue.
    – Kilisi
    Dec 1, 2018 at 17:35

1 Answer 1

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Yes, two 4x4’s would work fine to support two swings, provided 1) lumber is “Select Structural” grade and 2) fastened so they don’t rotate.

1) Make sure there are no large knot holes so that it is of the highest grade of lumber.

2) The “beam” is strongest when the 4x4’s are stacked on top of each other.

To test my calculations, I’d try testing them out on some short blocks with a couple of children standing/sitting on them.

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  • Great idea to test. I'll test with adults, I fully intend to be one of the swing users.
    – Kilisi
    Dec 1, 2018 at 19:47
  • Four adults standing on it on blocks and it looks like it will be fine, I'll reinforce with metal wraps in additon to bolts when I get started to prevent any movement.
    – Kilisi
    Dec 1, 2018 at 23:15

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