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Tree house build

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  • Tree house build

    Kids asking about a treehouse for a while, so without much planning we headed to the store and picked up some lumber. Click image for larger version

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    Here's what I've got so far. Two 2x6 pressure treated boards spanning 4 tree configuration. Each end has two slots 3 inches wide to accomidate independent tree movement which 3/8 lag bolts go through into tree.
    After building the 2x6 decking that would float above it, I realized the base isn't nearly strong enough to hold a heavy stick built structure above it.

    I know they sell special tree attachment bolts for something like this but I'm too cheap to fork out $500+ for them.

    I plan on doubling up to 4 planks and possibility going to 2x10s for more strength.
    I like the idea of the slots to allow for movement but now think it weakens the planks too much to incorporate this design.

    I have a 6 ft piece of 3/4 dia all-thread rod that I plan on using for support somehow, but am worried drilling through the tree would kill it.

    Can you lend some insight on how stout my bolts and base need to be to accommodate this load?

  • #2
    I'm excited to see how it works out. I guess you could research fasteners in trees to see what's the best aproach. Enjoy the tree house!

    Simpson has some structural screws you might be interested in. I think you want to make indirect connections creating framework to fit around the tree trunk that allows for expansion and movement.

    Last edited by Mightyservant; 04-19-2019, 12:26 PM.


    • #3
      You may want to check and see if you need permits before you start. At least once each year there seems to be an article in our newspaper about some city in Canada or the US that comes down hard on somebody who built a tree house after a HOA notices or some a neighbor calls it in.


      • #4

        As you can see there is loads of info out there. I found the above with only a few minutes of searching.

        Last edited by Bob D.; 04-19-2019, 01:47 PM.
        "It's a table saw, do you know where your fingers are?" Bob D. 2006



        • #5
          Yes, I have visited those sites already but they aren't much help to my situation.
          Like I said, I don't want to fork out upwards of $500 for their tab bolts.

          No worries about permits, I'm on 5 acres with no neighbors in sight.


          • #6
            Yeah they are pricey, but you could probably roll your own easily enough for a lot less and get the same affect.
            "It's a table saw, do you know where your fingers are?" Bob D. 2006





            • #7
              Most mount designs I've seen use a huge bolt on one side of the tree. The load causes a prying down(angle) motion which seems to be why bolts need to be huge in diameter.

              If I use a 3/4 dia threaded rod all the way through the tree, I can put planks on both sides of the tree and devide the load in half.
              This should double the shear strength but I'm not sure a 14" tree can survive having a 3/4" hole drilled all the way through it.


              • Mightyservant
                Mightyservant commented
                Editing a comment
                I really don't have any idea about fasteners in live trees, 14" diameter I think would matter depending on the species and precedent. Might be safer for the tree to use a galvanized bolt or rod versus cadmium plated, it just a guess though.

                There are 3/4" lag bolts which could be driven from opposite sides.
                Last edited by Mightyservant; 04-20-2019, 11:13 AM.

            • #8
              3/4" x 12" SS Lags Screws can be found on McMaster-Carr and other places. Not cheap but less than the TABs.
              "It's a table saw, do you know where your fingers are?" Bob D. 2006





              • #9
                Not a bad idea, but I already have 3/4 gal threaded rod on hand. I'm thinking I just need to make a sleeve to go over the threads for strength and a boss to space it away from the tree.
                Then I'll have 2x10s on either side of the tree and the load will be shared evenly.

                12" would be too long. Largest of the trees is 14" dia the other 3 are about 10"
                I don't care if I kill the smaller trees, its just the 14" pine I'm concerned about.
                (Btw, the diameters are measured 10ft up from ground.)

                Thanks for your advice, I'll let you know how it goes next week.


                • #10
                  I would.sleve the all thread with emt conduit. Doesn't add much to the hole. Or plumbers, a wrap of 10 mil tape like we use on udergroud gas pipe.

                  Look at all the weight that power poles support with much smaller bolts.

                  You could also go with riser clamps and saddle around the tree. Or make your own saddles with a 4x12 half notched.

                  I've done a lot of zip lining and they tend to use wraps around the trees. Not so much as through bolts. Are there larger limbs to support with straps from above?

                  Not that I live in a Forrest, trees are pretty much self healing as long as you don't use copper for your attachment points.

                  Now the question is, will all 4 trees grow at the same rate, or will you have to put leveling legs into your design. Don't want their pitcher of koolaid spilling.

                  phoebe it is


                  • #11
                    Thanks Rick, some good food for thought.

                    I was thinking 1/2 black pipe. Emt will probably collapse when I tighten the nuts.
                    The pipe only needs to go about 2in into tree to prevent the rod from bending where the threads are narrow. I like the tape idea. I might use it between rod and pipe sleeve.

                    Riser clamps would be difficult to find the exact diameter for the tree. Besides, probably not strong enough for upwards of a ton of downward force.

                    No overhead branches anywhere close enough to use cabling.

                    No worries about growth rate of different trees because trees grow from the top. The trunks get thicker but my anchor spots will never vary in height.


                    • #12
                      Wow! I would love to see the outcome of it. Also for the best suggestions and designs you can take help of the professionals from this site too. So, that you can get the alternates and shortcuts also for the unique build. All the best!
                      Last edited by Bob D.; 10-05-2019, 01:03 PM.


                      • #13
                        Click image for larger version

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ID:	741531 ​​​​​​My attachment points, 3/4 threaded rod through tree sleeved with black pipe for shear strength and torqued down nuts/washers on outside.


                        • #14
                          Click image for larger version

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                          Almost finished. Either side of tree are 2x10s. House is 6x13' with 2x6 floor joists which float on top of the 2x10 planks to allow for tree sway. The floor is about 12' off the ground.


                          • #15
                            Looks good, I am sure the kids will enjoy it. What limits the lateral movement of
                            the structure if the floor joists are floating on top of the 2x10 beams. How did
                            you secure the structure against upturning from high winds.
                            "It's a table saw, do you know where your fingers are?" Bob D. 2006