Substructure for playhouse in the sky


Old 03-29-10, 09:45 PM
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Join Date: Mar 2010
Posts: 1
Substructure for playhouse in the sky

I would like to build a playhouse about 6 feet off the ground. It is to be 12x12 or 16x16 feet square. The 16x16 would have a four foot porch on the front and a side. I have some 4"x6" treated post, but I'm not sure how many I need and the spacing of the floor joists and the size. The cost will probably dictate a 12x12; 4 feet on one side for a porch. Please help! I have been to a chart of the above question, but did not understand it.
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Old 03-30-10, 07:15 AM
Join Date: Mar 2000
Location: Arlington, WA
Posts: 9,238

Welcome to the forums.

You need to treat it just like a deck. At 6 ft. above grade, you'll need side walls or railings, and they have to meet code. That means a min. 42" tall and no opening large enough that a 4" ball can pass thru it. It'll have stairs obviously, sou you'll need guard rails on both sides of those, plus a hand rail.

4X6 posts will work fine. Their spacing is detwrmined by the size of beam they are supporting. the spacing between the beams is determined by the size and spacing of the joists that THEY are supporting. Joist spacing is determined by the flooring that you will be using. So you need to start with the flooring or decking requirements and work down from there to determine everything else.

1X or 5/4 X 6 deck boards need joists spaced no more than 16" apart. 2X6 joists (DF or SYP) spaced 16" OC can span 10' max., sou your beams need to be no more than 10' apart. If you use 4X6's for the beams, you'll need post spacings of 6' or less, so you would need 3 posts under each beam. If you use 4X10 or 4X12 beams, you could support each with 2 posts.

Footings for the posts should be 16" square and 6" deeper than your local frost level. IF frost isn't an issue, make them 16" deep. Install post bases or column bases in each footing (Simpson PB or CB whatever -- I use CBSQ's almost exclusively) and install your posts in those.

Since it's freestanding, you'll have to crossbrace the posts and beams in both directions.

Local codes requirements will take presidence over anything I just told you. CHECK THOSE FIRST!!

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