Treehouse advice

Hi, all. I drew up some plans for a treehouse in our back yard and would like your advice. I included the sketch here. The idea is to use 3 (pine trees that form a triangle, using 2 beams, with the treehouse sitting on top and some space between the walls and trees; treated southern pine lumber for the frame (mostly 2x4s) and plywood for the walls, floor, and roof, with maybe steel roofing panels. The two beams will need to be 12' and 14' long, about 7' to 8' high above the ground, and the treehouse itself will be almost exactly 8' x 8' x 8'.

I'll take any criticism and suggestions. One question I have is what size beams to use and how best to attach them to the tree. I was thinking 2-by-something treated lumber, maybe thicker or paired if one isn't enough for each beam, and a lag bolt on the one tree (on the left in the sketch) and flexible attachment to the other two trees to allow for tree movement.

 

Visit tree house building websites. There is a whole series of products and techniques to do what you want. There are special attachments that go into the trees to minimize damage to the tree, carry the most weight and allow the tree to grow. In your design you also need to accommodate movement of the trees. If you try firmly anchoring your support beams you'll likely have them torn apart by a storm blowing the trees around.

 

That was my concern - pines tend to sway a good bit when the wind picks up.

 

Built a platform for my kids in the back yard, had a very unique oak that grew up with 5 trunks all similar size.

Anyway after about 3 years all the joists had pulled out due to all the trunks swaying in the breeze. Eventually had to pull it down so movement really has to be considered.

 

Thanks for the tips. I already visited a number of treehouse websites and read a number of articles and guides -- that helped me come up with much of this design. I wanted to see if anyone sees anything I may not have thought about.

For each of the two beams, the plan is to have it rigidly attached on only one end, with the other end resting in a flexible bracket to allow tree movement. (I'm thinking of using 3/4" x 8" lag screws.) In terms of beams, I'm thinking I can use 2' x 10' or 2' x 12' beams; they're going to span up to 14'. From what I've researched, that should support the worst-case total weight of the treehouse including live load with people in there, and then some.

One question that occurred to me is whether there's a chance the treehouse could "tip over", coming off the beams, if somebody really heavy, or multiple people, stood at the front or back corner of the floor, on the left side. I guess I could attach cables from higher up the tree to the rim joists at those corners, as some treehouses have, or somehow ensure the joists would be strongly fixed onto the beams. I'd prefer the latter if it's just as effective, or if the "tip over" possibility is something that's close to impossible.

 

One thing you've probably learned from many of the tree house sites is that lag bolts are generally not used. They can be but are on the lighter, cheaper end of the spectrum for attachment. Many sites consider them inadequate for supporting a "building" type treehouse. Some of that depends on how they are used.

Yes, I agree that you should be concerned about the structure tipping over or being lifted. Many sliding brackets go around their support pin to prevent them from lifting off.

 

I realize I'm getting to this really late, but if it were me, I'd support 2 ends using tree mounts and the third corner using a cable suspension system. My concern would be that over time, with three fixed tree attachment points I would run the risk of some weird twisting action in strange breezes.

But I'm not an expert, it may be that my concerns are entirely unfounded. My reason for doing it that way would be to try to over-compensate for my lack of actual professional knowledge on the subject. My view on treehouse supports is that while using 2 trees is twice as complicated as using one and using three trees is 3 times as complicated as using 2. (thus being 6 times worse than a single tree)

 

Thanks, Erik. I changed the plan since that post. I built it using only two trees, each having a V-shaped support structure with three 3/4" lag screws about 18" apart from another vertically (for a total of six screws), with four 2x10 beams on which the deck is attached. It's pretty much done except for some interior wall panels and floor covering (probably vinyl), and it seems to work well. It even held up against the high winds we recently had thanks to Irma. Now if only my truck hadn't been in the path of a falling tree!