thoughts on my first tree house – mid construction

So far I’ve finished the platform, wall framing, roof joists, ridge beam, rafters, sub floor, and am 90% done with the roof paneling. Still undone is wall sheathing, exterior siding (I’m considering cedar shingles), windows, doors, and other various finishes. I wanted to make a couple of notes for myself to remember and for any other perspective neophyte treehouse builders.

If you’re an accomplished carpenter, much of this will be child’s play to you.

My current level of progress. I have to work all day so I spend a lot of time looking out the window planning my next move.

About 1/3 of what you’re doing is abnormal-treehouse engineering and 2/3 is standard home construction. In practical terms that means that for the treehouse-portion you’re stepping outside of the realm of typical construction principles you can get from a book. You’re dealing with a platform, not a foundation. You have tree attachment bolts, (again) not a foundation. But once you lay the sill plate and start going up you’re pretty much back into normal construction.

When working with the treehouse-part you’ll need to use real rigging and real treehouse supplies. When working with the normal-construction-part you’ll want to follow standard building codes even if you’re building something small enough that it doesn’t need a permit. This book taught me a bit, but eventually this is the one I’ve been reading nightly to plan out the next day’s work. If you’ve built homes to code before then you probably can skip this, but maybe not if you’ve always ordered trusses and now need to cut your own rafters. The $18 for a book is easily money saved compared to wasted building materials or worse.

In the treehouse-part you also need to deal with the fact that trees move and exhibit dynamic loading which will transfer to your house. They also grow but only in thickness: the only upward movement is at the top. A branch at 10 off the ground will always be at that height on the trunk.

Figuring out how to build a gable roof and make your rafters has nothing to do with a treehouse. It’s pure construction, and based in math you learned in middle school.

Getting the floor on is really important. I’m pretty comfortable these days hanging in space from a rope and can ascend/descend fixed ropes with comfort. But it’s still a terrible way to do work. It’s hard enough to do quality work and get things level and even when standing on the ground. Add in the idea of dangling in free space while you do it and it becomes extremely difficult.

Take even simple things like driving a screw with a drill. Most of the screwing is the result of you applying force to the drill as much as it’s the rotation of the device. But in free space as you push with the drill you get pushed away. It can be quite the feet while suspended to be able to apply lots of pressure and not get pushed away from the drill.

Building codes are not stupid. There are cool new forms of construction that I’d love to experiment with but if you’re doing wood frame construction you should really follow code. There’s the safety and durability aspect but there’s also the fact that everything is expecting you to do it a certain way. 16″ on-center studs as an example provide plenty of space to get a drill in between them. If you change it to 12″, maybe it won’t. Ditto for roof joists: my ladder is conveniently designed to fit perfectly between 16″ on-center dimensional lumber.

There’s also just some rad ways that carpenters have figured out problems and you’re dumb to repeat the mistakes they’ve solved for. Building up a corner post using scrap pieces as an example: genius.

There are some small areas where you can deviate but realize what you’re doing. 2×4’s aren’t normally used for roof rafters, but most people don’t have houses that are 5′ wide. And the span calculator says 2x4s are fine for that distance, so it’s not like we’re inventing our own engineering models here.

Unless you make some deathtrap structure out of pallets and duck tape, you will use a lot of wood.

You will need to be your own engineer. From a sailing and rigging background I knew what a working-load-limit is, I know Crosby makes great hard goods, and how to size my turnbuckles. This is the area where you won’t find much love in the home building books or building codes.

Don’t be your own engineer if you can avoid it. There are some great resources out there (like the American Wood Council’s Span Calculator) that will help you make good decisions and take the guesswork out. Better, they keep you safe.

Plan out your materials the best you can. To some extent you can piecemeal your treehouse, not really knowing what you’ll do until the evening before the following day of construction. The downside to this is that you don’t know the materials you’ll need. In my small town this is a problem because although we have a kick ass lumber store it’s still small and they run out of things sometimes. And if you’re mid project and missing that one thing (and you’re not following a plan that has a building inspector checking on you), you might just wing it and do some rather ghetto fabulous jenky work.

It’s also a pain in the ass to drive back and forth to a hardware store multiple times, double that if you need to haul lumber or roofing panels around. Try as much as possible to at least get the big items delivered. Hundreds of pounds of lumber. Guillotine-sharp corrugated metal panels. Multiple full sized plywood sheets. Plan out what you need, get as accurate an estimate as possible, and maybe consider adding 20%. Same for strong ties: not every store is going to have the 28 ridge-rafter ties that you’re looking for.

I used 10 pounds of #8 3″ screws. These would be very annoying and expensive to buy in small boxes. Additionally, I have 5 pound bins of a variety of others nails and screws. Then there’s the 1/2″ bolt fasteners.

Strong ties everywhere, but not the ones you need. When people buy strong ties they tend to buy dozens at a shot.

The amount of tools needed isn’t too extreme but you’ll need some, and others make quick work. The platform construction, along the massive HL-55 brackets required big automotive wrenches and my impact driver. If you’re not doing lot of automotive work you can skip the impact driver and just use two wrenches. For the tree attachment bolts, my buddy loaned me his huge right angle drill. You can probably get by with just a normal corded drill, maybe?

Tools that I’ve been using like crazy and you should probably own yourself:

  • Jigsaw. While the circular saw is probably going to see more action the jigsaw is easier to move since it’s probably on a battery and allows you to make some quasi-artsy cuts. You’ll also need it (or a handsaw, if you’re a masochist) for bird mouth cuts if you do rafters. It’s also easy to swap out to metal blades if you need to slice up some corrugated metal roofing.
  • Circular saw. It makes straighter cuts than the jigsaw and it’s easier to follow a line since it clears its own dust so well.
  • Pencil. Decide early on whether you’ll be cutting the line, cutting above the line, or cutting below the line. Being randomly 1/8″ off everything isn’t going to work.
  • Tape measures. True zero and a rougher carpentry one. Again, the wiggle at the end of your 25′ tape measure will allow you to be just a smidge off. Also, get a speed square.
  • Level. The treehouse moves but on a windless day try to get the platform flat. You can also run a string between the trees and using hanging levels to determine where your tree attachment bolts should go. Tie twine around the trees to get the angles, height, and orientation for your tree attachment bolts. Using hanging levels on the twine so you know the platform will be level.
There’s nothing “tree-house-ish” about building rafters. It’s just a staple carpentry skill.

Working on a treehouse is a great way to get hurt / killed. I read in my construction book about people being sketched out on ladders and when working on the roof. How about working on a ladder while above the roof of a house that’s above the ground? Some points on safety:

  • Until the top plates were on I wore a harness everytime I worked on the treehouse. When going onto the roof, I’m roped in again.
  • Once you start doing the roofing materials themselves on a steep slope roof (mine is 45 degrees or 12:12) it becomes very slippery very fast. Working with corrugated metal you effectively have an unguided guillotine. If one of those panels slides off and impacts someone the results would be horrible.
Power tools, heights, and sketchy working conditions.  OSHA not-approved. In my defense I have a static line above, vt prussik max-over-one, and a locker.

It takes a while. I was talking to a construction guy the other day and he commented that a small building takes about the same amount of time as a large one. It’s shifting between phases (roofing, walls, cutting plywood, etc) more so than the length of each phase. Doubling the square footage of a building doesn’t really appreciably increase the time.

You probably don’t have to deal with electrical, plumbing, or hvac so it’s definitely quicker than normal home construction. But don’t think it will be quick. You’re still cutting rafters. Instead of 16 you might need 12: that’s what, maybe an hour’s difference in cutting and install time? In both cases you need to measure the rafters, make good cuts, shop for strong ties if you’re using them, and haul the wood up there. It’s probably a most-of-the-day affair, regardless of 12 or 16.

You’ll be bad the first time you do something. This is a lesson I’ve learned to embrace in my life. It’s just a sad reality that can’t be avoided. If you’ve built a lot of structures before then you’ve made the mistakes or had someone stop you before you got too far along a bad path. But on your own trying to follow books and youtube videos you’re going to screw things up. For me this meant starting with this treehouse before I build the one I really want to construct. I feel a lot more confident on my next one. I’ll still make mistakes on that too but hopefully they won’t be as large.

Mistakes compound work. If you build a true and straight structure, when you go to put the walls and roofing material on it will fit like a glove. Zip some nails or screws in and you’re done. But if the plywood is all wonky and won’t fit well you now need to spend time fixing your problem with shims and various jenky workarounds. Be as accurate as you can be because you will transmit errors up through the building process and constantly have to address them.

So far it’s been totally worth it. There’s always a lot of good reasons not to do something. Before this I never cut a piece of wood beyond a 90 degree angle, I certainly never tried to make rafters. I’ve never put a roof on something and I didn’t even know that a right angle drill existed.

If you have the desire to learn and can appreciate the process as much as the result I think you’ll dig building a treehouse.


  1. There are treehouses, and treehouses. I remember our treehouse when I was a kid, back in the early 1980’s. The tree was a big solid cherry tree, probably 30 feet tall. The treehouse was maybe 20 feet up.

    The floor was a 4’x8′ sheet of plywood (probably 3/4″ or 1″) nailed to two 2×4’s that were nailed to a couple of branches apiece. The 8 foot sides had railings, probably 2.5 feet high, made of more 2×4’s. I don’t remember whether there was a railing across the back; there wasn’t on the front. Also on each side were two more 2x4s arranged in a big V and nailed to the floor and railings, holding up the corners of a flat plywood roof (we generally got a few inches of snow at a time). It was not painted. To get into it, you climbed the tree.

    I barely remember when it was constructed – my father and maybe a neighbor dad wrestling the plywood up the tree, probably with clothesline looped over a branch.

    That treehouse lasted almost ten years; my brother and I spent many hours in it, until we were 16 or so (about 200 pounds apiece). It always felt solid. Fond memories, good times…

    Yes, it was dangerous. But I’m not sure it was more dangerous than my current daily bicycle commute. And it was safer than things I saw at Burning Man a few years ago, including a ladder made of non-climbing rope for the verticals and closet-rod dowels for the rungs. I’m not sure what was most dangerous in that camp – that ladder (which broke and dropped someone, and they kept using it), or their zip line (one person was very lucky to walk away – the first cable clamp slid 6″ along the 3/8″ cable from his momentum, then he did a vertical loop and fell onto the wreckage of the steel tubes he’d just crashed through), or the lightning storm during which several people stood in bare feet in mud next to a guy wire attached to the tallest structure on the Playa (I heard that someone in another camp got zapped during that storm but survived).


  2. Chris that tree house sounds terrific that your dad built.

    That ladder at Burning Man sounds absolutely nightmarish. The only way I feel comfortable getting up high is if I have full trust in my systems otherwise I stay squarely on terra firma.

    Working on this treehouse I’ve done some super-jenky work, balancing a ladder on a ladder and things like that. But I was roped in and I wouldn’t have fallen much or pendulumed that far. Now that I think about it, despite all the terrifying non-OSHA type work I did I never fell on my rope. I suppose the shockingly dangerous is probably still okay, emphasis on the probably. But yeah, no mud pits in a lightning storm for me.


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