Treehouse / deck - right size posts and joists

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Topic by gbarron1 posted 03-29-2013 02:17 AM 60913 views 1 time favorited 7 replies Add to Favorites Watch
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2 posts in 2152 days

03-29-2013 02:17 AM

I’m building a free standing treehouse out of mostly recycled lumber from a deck I had rebuilt last year.
It will be a 16×16 deck with a 12×12 fort atop the deck. Probably 6 feet above the ground.
I’m building over a 9×12 concrete slab that was just sitting there when I bought the house and I’ll dig post holes and use concrete footings to complete the 16×16 footprint.
Most of the 2×6 deck boards were salvaged but the 2×8 joists were hauled away. Are 2×6’s sufficient for joists?
How about 4×4 posts?
How far apart should I space posts?

Thank you

View GaryL's profile


206 posts in 3000 days

03-29-2013 08:42 PM

You would need three headers/beams to support the deck with 2×6 joists. With it being elevated there also needs to be diagonal bracing from the posts to the beams and deck.
Have you checked with the building dept? They could give you more info as well.

-- The difference between a pro and an amateur, an amateur points out his mistakes

View gbarron1's profile


2 posts in 2152 days

04-03-2013 02:12 AM

Thanks for the tips.
I’m going to use 6×6 posts, double 2×10 beams in notched posts and 2×8 joists. And diagonal bracing as Gary mentioned, possibly also under the joists.
I’m wondering about the spacing of the joists and posts.
My initial plan was to space posts 4” apart in all directions. That would require 20 posts. It seems like overkill but I’ve already bought the joists and from what I’ve read, I can’t span 16” with them.
Any suggestions would be appreciated.

View dbray45's profile


157 posts in 1768 days

02-18-2015 02:39 PM

gbarron – I would use 16” on center for the joists. If you are going to use a composite for the decking, 12” may be in order.

Luong – It seems that you have the same comment for every post on this site – you need to call a contractor in order to do it right. Well, some of us are or have been contractors and others are looking at doing it right – where poor contractors did something stupid in the past.

If you are not going to offer real advise – then don’t offer anything.

This goes for millicater and rhonan as well.

Just my 2 or 3 cents.

-- Love woodworking and fixing most anything

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01-19-2019 08:37 AM

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13 posts in 23 days

02-03-2019 03:05 PM

Interesting post. I Have Been wondering about this issue, so thanks for posting. Pretty cool post.It ’s really very nice and Useful post.Thanks ?????

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02-10-2019 10:44 AM

i really like this article please keep it up.

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02-12-2019 08:13 AM

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