I've started a playhouse for my kids on a figure-it-out-as-I-go basis, and I finally hit the point where I'm recognizing how little I know about what I'm doing.

My specific question is what's my best option for a floor.

My first thought was to use SYP 2x6x10s, then I started worrying about how much weight that adds and thought SYP 1x6x10s, but I'm finding that those are hard to come by plus I don't really see anyone else doing that. It looks like most folks use plywood, but I need this to stand up to weather without a roof on it for a few months to a year, as we sort of build this through different iterations for different seasons of our kids lives. This first phase is going to be sort of an open air play deck with a climbing wall where they can make their own little tents and up there, on just an elevated deck surrounded with safety rails.

What I've got so far:

Pressure treated 4x4s, set in concrete 2 feet deep, three on one side and two on the other in an 8x10' perimeter, surrounded with 2x6's connected on the 10' side with half inch bolts at the corners, and on the 8' side with 3.5" 5/16 lag screws. My joists are 8' 2x4s at 17 inches on center, hung with joist hangers tapped in with 6 2.5" nails per hanger, and two 3.5" deck screws on each end. On the end with three 4x4 posts, a climbing wall to the top made of SYP 2x8x8s attached with 3.5" 5/16 lag screws.

Have I made any terrible errors so far?

What should I use for flooring?

overview of playhouse deck

1 Answer 1


If it is open air then i think you construct just like a deck with 2x6 deck boards so water can get through. Either pressure treated, trex or cedar/redwood.

Your 2x4 joist appear to NOT be treated. I would use treated 2x6, unless it will not be in the elements for long.

Why 17" on center, that is an odd number?

  • 1
    Thanks! 2x6 seemed like the way to go to me too, as long as it won't be too heavy. Logically I figure the 1/2 bolts and 2x6s should be more than adequate, just wasn't certain. Given my strong preference to not replace all of these untreated 2x4s, what if I just replaced three of them with treated 2x6s and painted with exterior paint? 17" OC because I divided 7 (# of voids created by six 2x4s) into 120" and got about 17. I figured it was in between 16 and 18 and not too inherently wonky for this application other than it being a weird number. Aug 9, 2020 at 18:06
  • Partial "nevermind": I'm just biting the bullet, taking your advice and swapping those joists for 2x6 PT SYP, then I'll put same on top as deck boards. Going to add three more 4x4s just for good measure, two in the middle of the 10' sides, one more on the other 8' side. After that I'll be more worried about our house falling down than I am this thing. Let me know if you think of any other advice - thanks again! Aug 9, 2020 at 18:28
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    If you want to save a buck, when you swap out the the regular framing for pressure treated, use the regular for the rails where they will be much easier to replace when they go bad, easier to monitor too.
    – Jack
    Aug 10, 2020 at 0:07
  • 1
    Thanks Jack, exactly what I was thinking! I wound up hearing about 5/4 PT decking from my father in law and went with that for the floor. Seems perfect. Aug 10, 2020 at 3:04

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