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I got a new swing set for my daughter which was standing just fine but has rotted feet I would like to replace. I would like to replace the rotted feet by cutting them off above the rot and joining with new wood. So, what is the best way to do this?

I have considered the half-lap joint, but on one tower (tower #1, the less rotted one) there is only about 6-8" of wood to work with below the metal climbing poles. On the other (tower #2) the feet are so rotted I will remove the poles and have to re-insert them into the middle of the new joints, which at least can be longer than on the other tower. I've read that for a roof you want joints that are at least 12" long, but I don't have that much room on tower #1 and I worry about inserting poles into the joints on tower #2. And of course this swing set will hold less weight than a roof, but certainly more than a fence.

Anyone have guidance on what sort of joints might be required for this work? Or another idea to replace these rotten feet (short of taking the whole tower apart)? I'd also rather not spend $200 on metal ties. Also, the existing wood is cedar (not sure which type) and the new wood will be locust (also not sure which type, but rot resistant).

Tower # 1

Tower # 2

Swing set completely assembled

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    how long should it last after repair considering the kids will grow out of it
    – Traveler
    Commented May 3, 2023 at 5:09
  • probably 10 years or so Commented May 3, 2023 at 5:42

3 Answers 3

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+50

You were on the right track. Cut the rotted part of the timbers off and a bit of the intact wood to join new post material using lap joints. This is a very strong joint. The idea here is to cut 1/2 way through the posts and the new material which provides as much glue surface to take advantage of the long wood grain. 8 or 10 inches of overlap would be plenty. Cut with precision as the more precise the cuts are, the stronger the joint will be.

You'll need to splice past some of the cross bars. There's no way around this as the wood they go through is rotten in some instances. You will have to replace the rotten wood. You can bore new holes for the crossbars in the new timbers and re-install them.

lap joint

You'll want to use waterproof wood glue and mechanical fasteners such as screws or bolts. Screws might be best as the exposed bolts could be a potential safety concern in that environment but bolts would be stronger. Don't skip the glue, that's where the real strength comes from in this joint. The mechanical fasteners are secondary in this case.

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    A pan-head bolt a little shorter than the total thickness of the wood, with a T-nut will produce the stronger connection and both ends can be easily sunk into the wood for no protrusions. The T-nut barrel needs to be long enough that the bolt can strongly mate with it entirely inside the wood.
    – jay613
    Commented May 9, 2023 at 1:58
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    If he can find a stainless steel t-nut or something galvanized that would work. He could also use stove bolts and bore out a recess for a locknut on the other side, but that might encourage water to collect in the holes. 5-6 3" wood screws should be plenty strong to hold it together until the glue dries.
    – gnicko
    Commented May 9, 2023 at 2:07
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    My swing set came with T nuts and bolts that far outlasted every other part of the set. Nothing ever rusted. The wood rotted, disintegrated, the kids grew up and moved out, the hardware is still sitting in a pile in the garage. I don't know what they were made of , they had a slightly yellow tinge. Yellow Zinc? Just a guess. It doesn't look like OP's set will last long enough for anything to rust. :)
    – jay613
    Commented May 9, 2023 at 2:11
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    Protecto couldn't hurt I guess, but it might not look very good. I think the waterproof glue would be enough for the internal surface in the joint. I'd consider applying some kind of surface coating (e.g. paint or spar) to the whole thing to help protect all the wood.
    – gnicko
    Commented May 10, 2023 at 21:00
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    Finding T nuts in sizes much larger than about 3/8" could be problematic. The bolts are secondary here. The glue is going to be where the joint gets its strength. Essentially the bolts hold the wood together until the glue dries.
    – gnicko
    Commented May 19, 2023 at 13:04
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Cut off just above that first layer of pipes.

Then either secure to pillars fixed into the ground (you can add some soft protection) - this depends on the total height you want.

Or make new "feet" with the original pipes and dowel them to the existing timber posts. The dowels can be 2" or 3" in diameter and you could add metal support bars (flat 1" 1/4' thick) across the joint and inset them into the wood so they are just below the surface.

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  • Dowels would provide enough lateral strength? Should I use some sort of construction glue? Commented May 3, 2023 at 13:21
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    Angle iron (2 pcs per leg, opposite corners) is also cheap and readily available. I’d go a minimum of 12” past the joint. Commented May 3, 2023 at 15:24
  • What would you say on the dimensions of the angle iron? There is some that is 1/2" wide by 1/8" thick, many other types are pretty expensive. Also, would aluminum work? Commented May 3, 2023 at 17:04
  • Additionally, how long should the dowels be? Commented May 3, 2023 at 22:01
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    Angle iron: I'd lean toward 1" per side, 1/8" thickness is fine. I'd be reluctant to use aluminum, as it's probably more expensive and weaker. Commented May 10, 2023 at 1:20
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cut 3.5 inches off the bottom of 4x4s and lay 4x4's on the ground. fill with sand .

Add. Make a sand box under jungle gym with 4x4s laying on the ground around perimeter. 4x6 can be used to if rot is higher

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    fill what with sand? Commented May 6, 2023 at 10:08
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    Your answer is not clear at all. Commented May 6, 2023 at 10:22
  • The rot is certainly higher in some places, up to 9" in a few, and this doesn't take into account how close it is to the bars on Tower #2. Also, I don't want to turn the play area into a sandbox - how does this solve the problem of replacing the rotten feet? Commented May 6, 2023 at 22:25
  • You are cutting 5.5 inches of rot off with out needing to add legs to keep same height. put mulch in it then you don't want grass. This is the easiest and best option
    – justin j
    Commented May 7, 2023 at 2:19

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