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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.

Note: this treehouse was built in summer 2009, taken down due to tree growth in fall 2013, and rebuilt in spring 2014. I've updated the text to reflect the (minor) changes I made, but there are a mix of old and new photos throughout.

Step 1: Pick your tree(s)

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 you see here (behind the magnolia!) has a trunk that splits into three at the base, and these trunks splay out somewhat as they grow upwards. At the height of the treehouse - about 9' (2.7 m) off the ground - one pair of trunks are touching, and the other one is about 4' (1.2 m) away. This means the design has been based on one for a closely spaced pair of trees, rather than for a group of three. The tree is a Garry oak, 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 trunks, each about 1' in diameter at 9 ft up.

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

Step 2: Design

The first photo is of my plan, which was sketched on a cereal box. I read around a lot first, of course: I found David & Jeanie Stiles' books especially easy to follow, and I also consulted the 1st edition of this treehouse book. 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 entrance platform that I hadn't originally planned. The 3D modelled picture gives a better indication of the layout of the main structure around the trunks.

Step 3: Materials

For this treehouse, I bought:

2 8' lengths of 2×8 pressure treated (PT) lumber
6 12' lengths of 1×6 PT decking material
6 8' lengths of 2×6 PT lumber
3 10' lengths of 2×4 PT lumber
3 10" long, 3/4" diameter galvanized lag screws and washers
2 8" long, 3/4" diameter galvanized lag screws and washers
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, except for the lag screws and washers which I got online. I also had to buy a really long 5/8" spade bit to bore the holes in the tree. The rest of the materials came from a neighbor's old fence: plentiful amounts of cedar boards and 2×4 lumber. It was used for the sides, so you can just substitute whatever you'd like to make a railing/walls.

The second photo shows the difference between the 1/2" lag screws that held the treehouse up for 4 years, and the 3/4" ones I replaced them with. A lot more steel in the big ones!

Step 4: Tools

The bare minimum of hand tools: hammer, saw, level, square, tape measure, adjustable wrench. Power tools: cordless drill, jigsaw

Useful but not critical power tools: miter saw (cutting lumber to length), table saw (ripping lumber), router (rounding edges).

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.

Step 5: 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 5/8" 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 6' (not 8', unless you don't want the entrance platform), halve the remainder, and make a mark this distance away from one end of your 2×8. Drill a 3/4" hole in the middle of the board. Make another mark using the between-the-holes measurement . Now drill two 3/4" holes, each 1-2" 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 a 2-4" 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, 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).

Drive the screws through the holes in the boards and into 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! I know my tree grew only by about 1/4"-1/2" in diameter over 4 years, but most trees grow faster than this. When I rebuilt the treehouse with 3/4" lag bolts, I gave it about 1/2" to grow on either side. I used 10" bolts for the trees with one bolt in them, and 8" bolts for the tree with two bolts in it.

Step 6: 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 small gap between boards for drainage. Cut two of your 2×6 boards the same length as the decking, and the other four to the width of your decking less the thickness of two of the 2×6's (which will be more like 1 1/2" each).

Step 7: Build the platform

Using 3" deck screws, attach the four 2×6's perpendicularly to one of the other 2×6'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.

Screw the other 2×6 to the other end of the platform, and check that it is centered and square. For squareness, measure the diagonals and ensure they are the same.

Step 8: Attach platform to supports

Now use the rafter ties to attach your platform to the 2×8s 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

As it is, the platform will wobble dangerously. Add diagonal bracing made of 2×4, 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 2×4 first. Use an 10" 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

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

If you don't have a suitably overhanging trunk or branch, you'll just have to make one. Lag screw a 2×4 (or similar) 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

Get up on your platform and screw down the deck. The only tricky thing here is cutting around the trunks. Use sheets of newspaper to make templates so you can cut out the holes reasonably accurately. Be sure to leave space for tree growth and movement.

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.

Step 13: Railing

I had lots of 2×4 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 2×4, laid flat, and screwed straight down into the uprights. I mitered the corners, and screwed the handrails to each other through the miter.

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. I used strips of 1×1 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 non-trivial to line up the railing with the sides of the platform.

Step 14: 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 pretty nice ladder. I leaned a couple of 2×4s against the entryway, cut the angle, and nailed on two thicknesses of cedar board all the way up. The plan was to put climbing holds up a wall, but I ended up just cutting 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 15: 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 16: Enjoy!

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

Update May 2013: I'm happy to report the treehouse is four years old now, it's suffered no damage from windstorms, snow, or tree growth (yet...), 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.

Update October 2013: Growth got to the point that I took the treehouse down for safety reasons. The tree started to open some joints, cracks had appeared in the main structural supports, and the washers were embedded in the wood. Amazingly enough, I was able to remove ALL of the lag screws, so when I rebuild I can reuse the same holes (and all the wood except for the 2×8s).

Update July 2014: The treehouse has been fully rebuilt. The instructable has been rewritten to reflect the rebuilding process, and there are a mixture of old and new photos throughout. Main changes: walls no longer have gaps, entry deck has been embiggened, and longer, heavier duty lag screws were used to give more room for the tree to grow. I anticipate it lasting at least another 5 years before taking it down again (probably permanently, as my kids will have outgrown it).

How did the tree react to the galvanized bolts through the trunks? Did it display any indications of health issues or weakening? I imagine I'd have used stainless bolts instead.<br>Great treehouse!
<p>Just fine. Here's a photo of one of the holes after I removed the 1/2&quot; lag screw when I took down the treehouse after 4 years. No sign of disease or damage; just some squishing of the bark when it couldn't grow any further.</p>
That looks good, thanks :-)
<p>Great guide, we are about to start our build this weekend and some of the information as been very useful. My biggest worry is getting the flat joists to lay against one trunk and out to another branch to provide the required base boards for the build. I think some wooden chunks inbetween tree and board might fix this. Oh well let's hope the weather holds, or the kids will go nuts.</p>
<p>Thanks. If you add end pieces to the main supports, they form a box and should allow you to avoid the blocks (which might damage the tree during movement). Best of luck with the build.</p>
<p>Do you know the (if any) size limits of this kind of construction?</p><p>Great ible btw</p>
<p>Thanks. It's going to depend a lot on the tree. If you have a couple of big trunks, it would be easier to make it bigger. But you will also have to scale up your fasteners.</p>
<p>thank you great inspiration for my tree house which has been destroyed in a storm so needs to be rebuild </p>
<p>welcome. Good luck with the rebuild</p>
Thanks good luck with yours
<p>Looks great! Definitely using this as a guide for next summers treehouse project. I had one question, why are the decking boards on the entryway flush with the top of the supports, as oped to being laid on top of them like regular decking?</p>
<p>(sorry about the slow reply) Good question. 1) it made the step up to the treehouse what felt to me to be the right size and 2) it was no more difficult to build.</p>
<p>thank you great inspiration for my tree house which has been destroyed in a storm so needs to be rebuild </p>
<p>thank you great inspiration for my tree house which has been destroyed in a storm so needs to be rebuild </p>
<p>thank you great inspiration for my tree house which has been destroyed in a storm so needs to be rebuild </p>
<p>thank you great inspiration for my tree house which has been destroyed in a storm so needs to be rebuild </p>
<p>thank you great inspiration for my tree house which has been destroyed in a storm so needs to be rebuild </p>
<p>Hi nice instructions but I am not clear on how you got the Tarp around the trees? Did you cut holes in the tarp? I have a similar spot with three tree trunks very close together but they petty much go striaght up and I can't figure out how the tarp will work. More pictures may help.</p>
<p>These trees splay outwards so they are separated almost by the width of the treehouse at the height of the top of the tarp. If your trunks stay close together, yeah, you will need to cut holes in the tarp.</p>
<p>super awesome. I would have installed supporting beams from the ground to the base of the house, instead of putting on the weight on the trees. I never built a tree house though so I don't know what I'm talking about. Excellent work.</p>
<p>Thanks. What you describe is not a treehouse, it is a house on stilts next to a tree. Remember that digging holes next to a tree will cut through roots... which is probably worse for the tree than putting a few small holes in it. If you want to build something like what you describe, I recommend seamster's <a href="http://www.instructables.com/id/Backyard-Fort/">Backyard Fort</a>.</p>
<p>Great job. I am getting started and your design looks like the best I have seen for my situation. In looking at your list of materials, you list 3-3/4&quot; diameter x 10&quot; long lag screws. Should the quantity be 4 instead of 3? How are you attaching the 2 x 8 to the other side of the tree trunk that has a 2 x 8 on both sides? Of course, the next question would be if you did add a lag screw where I am talking about, how do you keep that lag screw from interfering with the lag screw that attaches the other 2 x 8?</p>
<p>The 3 10&quot; long ones were used for the 2 trees at one end and for the braces. The 2 8&quot; screws were used on the single tree. Remember that these have to go through the 2 x 8 and leave some room for growth, so in the treehouse shown each of these penetrate the 12&quot; trunk about 5 1/2&quot; only. If your tree is smaller, you could simply offset the lag screws slightly in height. Good luck with the build.</p>
Thanks! Sorry, I thought the 2-8&quot; screws were to be used on the 2 x 4 diagonals. What is your opinion on 5/8&quot; diameter lag screws instead of 3/4&quot;? So far 5/8&quot; is the largest size I can buy individually.
<p>Well, this treehouse survived for 4 years just fine with 1/2&quot; lag screws, but these trees grow slowly and don't move much in wind. Fastenal.com has the 3/4&quot; ones available online.</p>
<p>do you know what property class have these lag screws? so I can know their resistance...</p>
<p>See <a href="https://www.fastenal.com/content/product_specifications/LAG.HDG.pdf" rel="nofollow">https://www.fastenal.com/content/product_specifications/LAG.HDG.pdf</a> </p>
<p>One other thing to note is...what kind of tree you are building this on? Pine and poplar trees are very soft and may lose the lag screws. Oak, hickory, ash and elm are much sturdier and will be structurally more sound. Look into what kind of trees you will be dealing with. Looks like fun. </p>
<p>Oak (see step 1)</p>
<p>Excellent work!</p>
<p>The only issue is that having the house attached to the tree it will always break in time. Trees are always growing and moving wiht the wheather. Google and find tecnhiques that will leave a treehouse free from the tree and lasting longer.</p>
<p>Of course, which is why this instructable contains information on how to mitigate these effects. If you're looking for a house on stilts that you can put near a tree, I recommend seamster's <a href="http://www.instructables.com/id/Backyard-Fort/" rel="nofollow">Backyard Fort</a>.</p>
<p>dreams come true:-)</p>
<p>Nice!!!!</p>
<p>nice </p>
<p>nice </p>
<p>nice </p>
<p>nice </p>
<p>i will play in thayre :)</p>
<p>Thanks, this is one of the best tree house instructables out there. I'm my first tree house deep in the forest where I have to hike all the materials in so I'm trying to do as much reading as I can before hand. I'm curious how your tree growth has impacted you design and if you would have made any changes because of that? I'm putting short galvanized pipe on my main bolts to make a sizeable gap between the tree and the frame of the tree house.</p>
<p>Ha, funny you asked; the tree has just grown to the point where I'm right now (well, on weekends) in the process of taking it down. I'm going to put it back up using bigger bolts (probably 1&quot;) and perch the treefort supports a little further away to give it more room to grow (see my commentary at the end of step 4). I'm not sure why you're adding the pipe, though - it won't help the strength any - or are you putting the supports on TOP of the pipe to allow movement at one end?</p>
I read about the pipe method in one of Pete Nelson's books, it basically serves the same purpose as a big stack of washers or the collar of a tree house attachment bolt. I'm probably not describing it well, if it all works I will post an instructable.
<p>Look forward to seeing it.</p>
<p>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.</p>
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. <br> <br>Here is a link to my Treefort: http://kurt-zeppetello.blogspot.com/2013/08/tree-house-or-fort-construction.html <br>
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.
Sorry, I see someone else asked this below, and you answered it!
Ha, well spotted, I'd forgotten myself. The fact that two people asked means I probably should edit that step to explain myself better...

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Bio: By day, I teach and document solutions to problems. By night... hmm. I should probably get out more.
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