I need to create a 15 feet span beam for kid swing (300 lbs load / 150 lbs and 2 swings assumption). One end will bolt to the tree (just for convenience).

What "treated lumber" lumber size and material I should use? Or is it better / cheaper to use metal pipe (from the plumbing department)?

I guess 4x8x16 or two (2) 2x8x16 would do it according to this website http://www.justanswer.com/structural-engineering/7vgxr-building-swing-set-16-ft-span-bolt-2x6.html. But I do like a clean look of metal. My wife would concern about big piece of lumber running on top of the kid (that looks heavy visually).

  • "that looks heavy visually"
    – Tyson
    Jul 10, 2016 at 13:07

1 Answer 1


I would use the 4X8. If I had not seen the recommendation that you have posted, that is what I would have suggested.

The round pipe is not suited for the support of weight. "I beams" and such are. The round pipe where the swing will be attached has a high potential the colapse. The round pipe can work if a truss configuration would be made of it, which would require welding.

  • 1
    I agree two a point, a 3" galvinised pipe will hold a 275 lb person and a 75 lb grand daughter on a 14' span. I built one. The problem is getting the longer pipe, I had scrap from a job and used that. The 4x8 will be cheaper and work well. I would not use 2x8's because of the flexing. Jack you are my age all the swings in parks were pipe when we were kids. + for the 4x8
    – Ed Beal
    Jul 10, 2016 at 17:17
  • I got to thinking, just after I posted that....swing sets are made with round pipe, that was a plus for using such as the OP hopes, but the spans that I was familiar with are only 6' or so and figured 15' would throw an entirely different dynamic in it. @EdBeal, 3" Sch 40 per your experience, may work for the 2 swings and would be available at the plumbing supply house. Also agreed on the double 2X8
    – Jack
    Jul 10, 2016 at 22:22

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