Treehouse Project: The Beams and Platform

Patent Pending #0257648891535

In case you missed it, see previous post on why I am building a treehouse HERE. To prove that anyone can build a treehouse I have posted a picture of the only other woodworking project I have completed in my entire life. About 5 years ago I needed a stand for my printer in my office so I built one from scratch. Not to brag, but while I've gone through multiple printers (e.g. Canon, HP, Brother) this stand has outlasted all of them. I’m sure your first thought was “This is most assuredly the workmanship of a skilled Amish craftsman!” I forgive you. 

I share this all in jest of course because who attempts to build a treehouse after building a printer stand like that? I didn’t know where to start so I did quite a bit of research on the interwebs but full disclosure my primary resource in guiding me through this project has been this book (Amazon link HERE). It’s pretty simple read with lots of pics (who doesn't like pics?) but it covers a lot of things you may run into and stresses important things one might overlook. It also contains a lot of creative ideas  - which is the fun part! I highly recommend it as a basic guide. Lastly, my advice to anyone attempting to build a treehouse is “plan ahead but expect the unexpected and be flexible”.  Every tree and treehouse is different, and almost nothing goes exactly as planned so get ready to use your power drill clockwise (to assemble) and counterclockwise (to undo mistakes).

The Beams, Wood and Hardware

So the most important part of a treehouse are the beams. You cannot skimp on this part because this is what will be bearing the weight of your house (and your children!) and so it must be done right. As Jesus said, it’s better to build on rock than sand or the house will come tumbling down (i.e. your foundation matters!). I decided to go with two 2’x6’ beams on each side of the tree. The two oak trees I was securing the beams on are about 7 feet apart. If the beams were spanning much more than that I would have went with 2’x8’ beams but combining two pieces of wood is much stronger than going with one thicker piece (4’x6’) because two distinct cuts of lumber will have varying weak spots making the combined piece stronger overall. Yes, King Solomon was right when he said: Though one may be overpowered, two can defend themselves. A cord of three strands is not quickly broken. (Eccl 4:12) The two pieces are secured by 4" galvanized carriage bolts secured with washer and nut on the other side (single bolt on right).  Don't skimp and not get galvanized. This is a non-negotiable. You don’t want water rusting your bolts over time and your structure is only as strong as the bolts holding them. For the screws I went with two ½” thick by 7 inch long galvanized lag screws and washers on each side for attaching the main beams to the trunks. This would ensure that even after going through the two pieces of wood there would be a good 3-4 inches embedded into the hardwood of that solid oak tree. 

level is key!

Now before you affix it to the tree you have to make sure that everything is level both across the beam and between both beams. Though time-consuming this step is very important because if it is not consistently level throughout the base the weight will not be distributed evenly and the final structure will be more susceptible to collapse. Don't trust your eyes! The leveler does not lie. I also highly recommend getting pressure-treated wood at least for the beams and platform. Water is wood’s worst enemy and so getting pressure treated wood will make everything last much longer than untreated wood will. Yes, it looks uglier (greenish tint), yes, it costs more, and yes, it weighs more but it is well worth the investment in the long run.

The Platform

The size of the platform will depend on the strength of the tree and the design of the house. I wanted to make it as big as possible without compromising safety and so the platform spans about 9x12 - stretching short of 2 feet beyond each trunk. That’s over 100 SF suspended over 10 feet in the air. Plenty big. I used pressure-treated 2x6 wood for this as well and doubled up the perimeter for additional strength and stability. The biggest challenge was calculating how far away from the tree the platform could span before requiring additional support. I’m trying not to use additional posts as it starts to feel less like an authentic treehouse and more like an elevated house next to a tree. Well, there’s no exact science to this but I went about 3.5 feet beyond the trees on each side.

Since at this time it was just me and my cousin Young working on this we weren’t quite sure how we were going to get the platform up and on to the main beams. We thought it would be easier to build the platform leaning up against the beams so we could just slide it up when complete. We used a 6 ft ladder to help us prop up the frame while we screwed it together. It wasn’t until after we finished this and were getting ready to hoist it up that we realized the ladder had become permanently affixed to the frame.

Do not try this at home...

Doh!! Like I said “expect the unexpected”. We unscrewed one corner and slid it out and tried again. We quickly found that with the frame doubled up on perimeter and with joists running across it was now too heavy to hoist 8 feet up. Mind you, we are both very strong men. =) 

pulleys are the best!

We had already set up some pulleys on each side to hoist the main beams and so we tied ropes around one end and my cousin got on the lower side and used the ropes like a cable crossover machine. Meanwhile, I was on the other end pushing the platform up as if I was doing a clean and jerk lift. Now imagine two out-of-shape men squeezing every aiota of strength out of their middle-aged bodies to get this platform up. I'm pretty sure we scared all the crows out of all the trees in a 3 mile radius when we released the primitive screams reminiscent of an olympic power-lifter....

Success!

However, when the platform was placed above the beams we noticed it would tip if there was too much weight on one side. To mitigate this we secured deck ties between the joists and main beams. After doing this I could stand on the edge with zero movement. 

deck ties galore

But just to make sure I also put in some corner braces at a 45 degree angle in each corner. Again, this is primarily to support the platform from tipping if there was too much weight on one side - highly recommended if you are going more than 2 feet over the beam.

Next week I’ll point out the essential  power tools you’ll need, how we put in the floors and also show the beginning stages of framing the treehouse. 

framing chapter next!!