How to build a treehouse

Picture of How to build a treehouse
This particular design requires two or three trees (or branches) in close proximity. It was made over the course of several weekends using new, pressure-treated wood for the support structure and floor and an old fence was recycled for the sides. The roof is a camouflage-pattern tarp. It's not weather-proof, but it stays pretty dry inside: a three-season treehouse, but best for summer! It was made with my 4, 6 and 8-year old children in mind, but has been a hit with visitors of all ages.
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Step 1: Pick your trees

There are definite advantages in using more than one tree for your treehouse - the treehouse can be bigger, and you have to use less bracing. The tree(s) you see here (behind the magnolia!) are a very tightly grown group of three trunks - they all touch at the base, and splay out somewhat as they grow upwards. At the height of the treehouse - about 9 ft (2.7 m) off the ground - one pair of trunks are still almost touching, and the other one is about 4 ft (1.2 m) away. This means the design has been based on one for a close-spaced pair of trees, rather than for a group of three. The trees are Garry oaks, and they don't grow much further north than this (southern Vancouver Island), so they grow pretty slow here. A solid gnarly collection of old trees, each about 1 ft in diameter at 9 ft up.

Start by figuring out how high you want the treehouse. 9 feet is exciting for kids but not scary. You can of course go higher, but you'll have to take more account of movement.

Step 2: Get your materials

Picture of Get your materials
For this treehouse, I bought:

2 x 10' lengths of 2 x 10 pressure treated (PT) lumber.
6 x 12' lengths of 1 x 6 PT decking material.
6 x 8' lengths of 2 x 6 PT lumber.
3 x 10' lengths of 2 x 4 PT lumber.
4 x 6" long, 1/2" diameter galvanized lag screws and washers
1 x 8" long, 1/2" diameter galvanized lag screw and washer
8 galvanized joist hangers
8 galvanized rafter ties
Nails, deck screws, pulley for 1/4" rope
Camouflage tarp

All this cost about $250 from the nearby Home Depot. The rest of the materials came from a neighbour's old fence: plentiful amounts of cedar boards and 2 x 4 lumber. It was used for the sides, so you can just substitute whatever you'd like to make a railing/walls.

The photo is of my plan, which was sketched on a cereal box. I read around a lot first, of course: I found David Stiles' books especially easy to follow. The design changed as I was building it - I didn't end up adding the braces drawn in the bottom left elevation, and I built an entranceway platform that I hadn't originally planned.

Step 3: Get your tools

Picture of Get your tools
The bare minimum of tools:

tape measure
adjustable wrench

A ladder is important, but even a stepladder would be OK if you installed a ladder/rope ladder/stairs to the treehouse early in the build.

Useful power tools:

Jigsaw (cutting decking and the movement-accommodating slot)
Cordless drill (driving screws)
Compound mitre saw (cutting lumber to length)

A jigsaw is probably the most useful additional power tool. I used the router to round off some edges, but coarse sandpaper and some elbow grease would work just as well.

Step 4: Mount the main supports

Get a strip of light wood and nail one end to one of your trees at a height about 1 ft lower than you want the floor of your treehouse (to save a future concussion, it should also be at least 1 ft higher than your head!). Get it perfectly horizontal with the help of a level and nail the other end to the other tree. Drill 3/8" holes straight into the tree just above the strip of wood. Do the same on the other side of the trees, this time taking the extra precaution of first ensuring the new strip is not only horizontal but also level with the strip on the other side of the tree.

Now, take down the strips and measure the exact distance between the holes. Subtract this distance from 10', halve the remainder, and make a mark this distance away from one end of your 2 x 10. Drill a 5/8" hole in the middle of the board. Make another mark using the between-the-holes measurement . Now drill two 5/8" holes, each 2" either side of your mark and both in the middle of the board. Get a jigsaw and make two cuts between the holes to make 4" long slot. Repeat for the other side of the tree. The slot allows the trees to move without tearing your treehouse apart - the more your trees move, the longer the slot ought to be (note that the slots I cut are only about 2" long, not 4", but these trees don't move perceptibly at the height of the treehouse, even in a strong wind. If your trees move appreciably, and/or if you're planning to build higher up, use a sliding beam support).

Now, screw your boards to the tree with a wrench. Use washers, and don't bolt hard against the tree. The space you're giving it to grow is the gap between the support and the tree. The longer you want your treehouse to last, the further you should perch the support away - and the more substantial your lag screws ought to be! 3/4" or, ideally, 1" would be best.

Step 5: Lay out the platform

Picture of Lay out the platform
Because the decking came in 12' long boards, I made the treehouse 6' long. So you need to cut the decking in half, and lay it out. Leave a 1/2" gap between boards for drainage. Cut two of your 2 x 6 boards the same length as the decking, and the other four to the width of your decking less the thickness of two of the 2 x 6's (which will be more like 1 1/2" each).

Step 6: Build the platform

Picture of Build the platform
Using 3" deck screws, attach the four 2 x6's perpendicular to one of the other 2 x 6's. Make sure they're spaced so that when you put it up in the tree, the perpendicular joists will miss the tree! With someone's help, put the contraption up in the tree, center it, and tie it down.

Step 7: Finish and square the platform

Picture of Finish and square the platform
Screw the other 2 x 6 to the other end of the platform, and check that it is centered and square.

Step 8: Attach platform to supports

Picture of Attach platform to supports
Now use the rafter ties to attach your platform to the 2 x 10s that you screwed to the tree (if the angles between joists are not exactly 90°, no problem, just hammer the rafter tie flat against each joist as you're nailing). Add the joist hangers. Use galvanized nails to attach these, not screws.

Step 9: Brace the platform

Picture of Brace the platform
As it is, the platform will wobble. Add diagonal bracing made of 2 x 4, and use a single long lag screw to attach both of these to the tree. It's easiest to just cut the 45 degree angle in the 2 x 4 first. Use an 8" lag screw here to make up for the fact that you're going through 2 thicknesses of lumber.

Note that I just used one set of braces on the single tree, because the other end had two trees and the wobble seemed insignificant. You'll need two sets for sure if you have just a pair of trees.

Step 10: Hang a pulley

Picture of Hang a pulley
A pulley is great fun for kids, but it's hugely helpful for hauling tools etc. up to the deck. Put one in now, and hang a bucket from it. A hefty climbing carabiner at the end of the rope is perfect.

If you don't have a suitably overhanging trunk or branch, you'll just have to make one. Lag screw a 2 x 4 between the two trees well above the deck (cut a long slot to accommodate movement, because you're higher up the tree), and have it protrude far enough to hang the pulley from. Bonus: you'll also have a ridgepole for your roof!

Step 11: Lay the deck

Picture of Lay the deck
Get up on your platform and put down the deck. The only tricky thing here is cutting around the trunks - leave a 1-2" gap all around. I used a compass (the type for drawing circles) to mark the jigsaw cuts.

Having a few ladders around is definitely handy!

Step 12: Add an entranceway

OK, so far the build has been very conventional - all the books on treehouses will tell you how to get this far. One of my favorite bits was the following minor innovation. The two big supports poke out far past the platform, and you can use one set of these to make a slightly lower level to use as an entry. Make a small deck between the tops of the supports to about 2' out, then build diagonally back to the corner of the treehouse. Add verticals. The pictures tell the story here. I just used offcuts - with any luck you'll be able to do the same.

Some of the offcuts came from cutting the excess 2 x 10 supports off flush at the other end of the treehouse.

Step 13: Railing

I had lots of 2 x 4 from the recycled fence, so I used two 40" lengths at each corner as uprights. I screwed them to each other first then nailed them to the platform. The handrail was also 2 x 4, laid flat, and nailed straight down into the uprights. I mitered the corners, and screwed the handrails to each other through the miter.

Step 14: Sides

Use whatever you like to fill in under the railing - rope, plywood, whatever. Kids probably shouldn't be able to slip through, though. I had lots of nicely weathered cedar boards which I just nailed up with gaps between. I used strips of 1 x 1 to hold them in place either side under the railing. The only tricky bit was the angled bit leading down to the platform - a bit of trial and error here, because it is tricky to line up the railing with the sides of the platform.

Step 15: Ladder

Picture of Ladder
The plan was to use a rope ladder to get up, but my 4 year old struggled with the transition to the platform, even though he could climb it just fine. So we vetoed it, even after making a really nice ladder (perhaps the subject of another instructable). I leaned a couple of 2 x 4s against the entryway, cut the angle, and nailed on two thicknesses of cedar board all the way up. The plan was to make a climbing wall, but I was shocked to find out how much the hardware cost - about $100 for 20-odd hand grips - so I just cut foot/handholds instead. I'd like to say this was free, but I wore out a big spade bit cutting the holes - it got too hot, and bent. This job was easy if a little time consuming to do - mark and drill two big holes, mark a line between them at the bottom and an arc at the top (I used a plastic bucket) and cut out with a jigsaw. This had really rough edges, so I rounded them off with my little router. That worked great, so I went around quite a few other edges on the treehouse with it. Smooth!

Step 16: Roof

I just strung a bungee cord between two hooks I put into the trees at about 7' above the deck, and slung a tarp over. This looked good, but in actual fact it made the roof too low at the sides. I have a compound mitre saw, so I cut four outriggers, screwed them to the uprights, and gave the treehouse roof a decent overhang.

Step 17: Enjoy!

The treehouse is a great little (36 sq. ft.) haven for the kids; they love it and so do all their friends.

Update 2013: I'm happy to report the treehouse is four years old now, it's suffered no damage from windstorms, snow, or tree growth, the trees are healthy, and it still gets lots of use. We've made a few updates over the years, adding a pirate's treasure chest, a swing, a braided climbing rope, a BEWARE sign we use out front at Halloween, and it's well-equipped with Nerf guns & water pistols. It's just big enough for two single air mattresses, so it's fun to sleep out in, too.

Thanks so much! I had already started all wrong and after seeing yours with the 2x10 underneath and freeing the 2x8 from the tree movement I was able to do a quick fix to make mine much sturdy. Thanks.

kurtzepp8 months ago
Thanks for you insight. I used your plans as a source. Although my treefort does not resemble yours on the outside, it does have some similarity.

Here is a link to my Treefort:
makendo (author)  kurtzepp8 months ago
Nice job, it looks great. You should consider writing it up as instructable (you've done all the work already!) and entering it in the Fort contest on right now.
rcotnam10 months ago
Sorry, I see someone else asked this below, and you answered it!
makendo (author)  rcotnam10 months ago
Ha, well spotted, I'd forgotten myself. The fact that two people asked means I probably should edit that step to explain myself better...
rcotnam10 months ago
How can rafter ties be used when the angle between the "perpendicular" 2 X 6 boards is not square (i.e. not perpendicular at all but several degrees off)?
makendo (author)  rcotnam10 months ago
If you look at the first photo in Step 8, you'll notice that the rafter tie is not flush to the wood as I'm nailing it. However, it provided very little resistance to widening the angle beyond 90°, so I guess I just hammered it open slightly as I was nailing.
jcdecker711 year ago
Just wanted to reach out and say thanks. My 11 year old son has been bugging me for a year for a tree house, and while I'm okay with tools, taking this task on was proving daunting. These are great instructions and I have modified based on needs. Got the joist attached to the tress today. Moving on to the frame next weekend. Thanks!
makendo (author)  jcdecker711 year ago
Thanks, I appreciate it. Best of luck with the build; let me know if you have any questions as you go along.
Good Father. Congratulation!!!!
dclose731 year ago
Question about the rafter ties. In my configuration, the 2x10s and 2x6s are not at right angles. How did you manage to attach the rafter ties? Did you somehow bend each of them to match the angle of the join? Or were your angles close enough that it did not require any modification?
makendo (author)  dclose731 year ago
Mine were pretty close, and yeah, I just hammered them flat. Good luck with the build!
this how-to was really easy to follow. cool stuff. The attached images showed my finished product. Kids are having a blast!
Just need the basket with the pulley now, and perhaps a zip line.

All fun stuff. Thanks,
makendo (author)  pedrozacharias1 year ago
Great job! Looks really good, and you have pretty much the perfect tree for it, too.
zilcho1 year ago
That is a legit tree house
this is great my dad keeps on saying he will make a tree house he never does
HollyMann2 years ago
You have some very lucky/fortunate kids to have a dad to make them so many awesome things! I love all your instructables - esp the bed - this one and the rubik's cube drawers! AMAZING!!!!!
makendo (author)  HollyMann2 years ago
Many thanks Holly, glad you like them. Making things for your kids is super rewarding, as no doubt you've found yourself!
I have 10 aceres. about 2.5 is forstry. I have 2 forts. 1 in the trees and 1 on poles me and my sis have wars. im still upgrading my forts with rails, shelves, airsoft gun turrets, ext
And i keep a dune buggy under it
what about grenades

that sounds absolutely incredible man, kudos to you
Winter-_-2 years ago
yikes. So many posts with people telling you off about how you did something or even someone just grumping about you "hurting trees" it has to be anoying- but im so impressed wih how each of your comments back are kind and to the point! :)
Its just so nice to see that even when others are being rude to you (and thats crazy as it is seeing that your posting a free gide and if they dont like it they can move on) your not lashing out.
Looks to me like your kids have two things to be proud of, a wonderful treehouse, and a dad who acts like a kind and levelminded adult. <3
makendo (author)  Winter-_-2 years ago
Aw, shucks. Thanks. The vast majority of feedback on this site is positive, fortunately, but this ible did seem to get some people quite indignant - probably for the wrong reasons. The same people don't seem to mind projects built out of dead trees! :)
cghale2 years ago
I'm at this point and am wondering the same thing as do you attach the 2x4s to the platform? Deck screws or something more substantial?
makendo (author)  cghale2 years ago
Deck screws are fine; just drive them through the 6x2 into the 4x2 brace. The decking sits on top and also helps secure the brace.
cghale2 years ago
For a house like this, what would the maximum safe width be? (i.e., between two trees) Working on this design now...
makendo (author)  cghale2 years ago
Not far at all. These trunks are within four feet, and don’t move much at all with respect to one another. If that’s not the case for you, taking account of movement is really important. The slots accommodate only a small amount of movement. If I was making a more widely spaced treehouse, I’d sit one end of the main supports on top of two really big lag screws (3/4” or bigger). There is a place you can buy them online now - The other end could be screwed directly to the tree, as I show here. Good luck with your build!
More bolts, in slots, please.
Three per tree in each board are recommended.
Two would be better than what you have.
The problem with your application is that the trees in high winds can exert a HUGE horizontal torque force on the bolt heads that could bend, tear out, or shear them.
What we did in our very similar situation was to drill several holes (just a bit bigger than the bolt diameter) next to each other in the boards.
Then we chiseled them out into slots.
Then added a bolt with a BIG washer in the middle of each slot.
This design allows the trees to move in high winds independent of each other without snapping or bending the bolts.
Also the bolts should NOT be tightened. The washers should be able to rotate. This allows the bolts to move side to side in high winds, and for the whole structure to "give" a little.
If you think of the tree as a huge lever, and the distance the wind can move it both ways, you start to understand the amazing forces at work here.
We love your treehouse.
Come to think of it, we love all of them.
makendo (author)  Ricardo Furioso3 years ago
I disagree about the "3 bolts per tree per board argument" - see this page for why. As for the rest; read step 4.
You're right about Step 4.
cowmanpoke4 years ago
 in step 4 when you bolt the wood to the tree, are you drilling all the way through the branch? i'm confused about how that wood is staying on
makendo (author)  cowmanpoke4 years ago
No, they go in about 4". A lag screw is basically a giant screw with a bolt head on it. So the thread holds it in place - in fact, once you've put it in it is very hard to move again. Use the biggest ones you can find, and perch the supports as far away as you can while still being structurally sound. In this treehouse, the supports are only about 1/2" away, because the trees are mature and slow growing.
Honestly think you might rethink the length of your bolts.
A foot, yes 12-inches, would be recommended.
Because that treehouse may outlive all of us.
Because kids will be in it.
Because kids will invite their friends.
Because whole scout troops or classrooms full of kids might descend upon it (both have happened to ours).
Because adults have a habit of frequenting treehouses along with refreshing adult beverages that make them do silly dangerous things. In groups.
I beg you to grab your socket and ratchet set, remove the 4-inch bolts, and replace them with big fat 12-inch galvanized lag bolts.
They're cheap.
It may sound like overkill, but the wind forces on treehouses are staggering, and if a storm weakens them, the next kids who venture up there could be in serious danger.
It is one thing for a kid to fall out of a treehouse.
It is another to have the treehouse fall or fail with a kid inside.
Thanks for considering this.
makendo (author)  Ricardo Furioso3 years ago
I appreciate that you're anxious about the children, but if the treehouse is going to fail, I suspect it will do so during a storm, and it is not occupied during such events. It's survived over a year without any untoward events despite some overloading you'd doubtless be appalled by and a 110 km/h gale. It certainly won't outlive all of us, as it will be removed when my kids grow out of it.
A 12" lag screw would go clear through the tree (especially if I put in 3 per board per tree, as you counsel; that would seriously compromise the structural integrity of the trunk). As for the "cheap big fat lag bolts" - perhaps you can point out a source for the benefit of others? I certainly couldn't find them in hardware stores or even online; the pros have them custom-made.
Congrats on the gale survival.
I suspect you're right about the failure.
I hope you are.
We found huge cheap lag bolts at Home Depot.
Putting a bolt through the trunk shouldn't compromise it's integrity. You'd need to predrill it, and the great percentage of the trunk—excluding the live cambium which comprises the outermost layers—is dead wood anyway.
Putting two or three bolts in a tree trunk vertically is a good solution if you do not have access to a custom fastener fabrication shop.
And it works just fine if you loosen the bolts annually to allow for growth and space between beams and trunk.
Werner1113 years ago
I would have added another bolt in for each tree, but it looks good :)
makendo (author)  Werner1113 years ago
I'm pretty comfortable with the bolts as they are for this little treehouse, but overengineering is no bad thing either. Better than putting extra bolts though would be to use bigger ones; this page explains why really well (and also points out that 1/2" lag screws are insufficient!).
Anyway, thanks - and I can confirm the treehouse is still standing :)
How do you secure the top of the bracing to the platform? Beneath it, on the outside, inside? I'm 15 and I have no idea what I'm doing... but decided that I really want to make a treehouse.
makendo (author)  andrewbhorton3 years ago
Beneath it and on the inside. Check out the hand-drawn plan and the second photo in step 9 (you can *just* see it). There are lots of other resources out there - on the web, books, etc. Best of luck in your build!

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