I am building a playhouse with swingset attaching to it. One side of the swingset beam (4x8x12) will be A-frame. The other side is attaching to the playhouse. I have a question about attaching to the playhouse though. Is it OK to put 4x8 beam directly on top of 4x4? I am planning to have the swingset to be 7.5 feet high max. So if I get 4x4x10, can I bury 2.5 feet of the 4x4 post into concrete?

I want to do something similar to this http://myoutdoorplans.com/playhouse/outdoor-playset-plans/ but their example is using 4x4 beam and the 4x4 footing does not have concrete footing.

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I imagine 4x8 beam would need to have 4x4 footing into concrete. Or is it not necessary?

  • I don't know if the 4X4 needs to be set in concrete. It depends on the soil conditions. I would have braces from the swing 4x8 to the other 2 4x4's. I don't see this in the picture. The braces even if only 2x4 would help support the lateral forces on the swing that a single 4x4 really can not support even if concrete is used.
    – Ed Beal
    Commented Jul 17, 2016 at 0:13
  • The website said to use 5" screws to secure the 4x4 beam to 4x4 post. I said it's not enough. So when you mentioned "braces", is it like two 2x4 on the side of the 4x8 beam to prevent it from bouncing and moving forward/back? I can put some 5/8" minus rocks on bottom. But even so, would a 4x4 post (attaching to a box in bottom using four 2x8 boards) + two 2x4 braces is enough to secure a somewhat heavy 4x8 beam?
    – HP.
    Commented Jul 17, 2016 at 3:25
  • The bolts going through the beam will hold it down but I think additional braces from the beam to the other 4x4 post will add stability. Even 1 2x4 from the Beam to the 4x4 on either side will increase the lateral support.
    – Ed Beal
    Commented Jul 17, 2016 at 14:54


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