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Have promised the kids a tree house - and now have to deliver!
The intent was always to build a platform rather than attach to the tree, however digging the post holes I found so many large roots that I think the dig would seriously damage the tree.
I'm planning an alternative as indicated in the photo sketch. Bolting the posts to a support frame that would sit on the ground. All posts and supports are large and heavy 150mmx150mm timber. Tree house platform will only be 1.55m high.
My questions to you guys are..
1) Do you think this freestanding design will be structurally strong enough without the posts concreted into the ground? I assume some diagonal bracing may help
2) What kind of fasteners would you use in positions 1 to attach the support posts to the frame on the ground and 2 to attach the sides to the posts. Assume bolts best over lag screws.
Thanks so much for your advice!!
Hello @mjkworldwide
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thank you for sharing your question about building a tree house.
There are several schools of thought competing for this particular assembly. I personally would probably do lap joins to join such large timber pieces together. In this way, I can use regular Zenith 14G x 150mm Galvanised Type 17 Batten Bugle Head Timber Screws - 25 Pack. I would also add a knee brace to all the upper and lower parts of the assembly. This will save you from having to put in large pieces of timber cross-bracing.
The next method is direct butt joins. Unfortunately, you'll still need to do a lap joint on the outer edge of the timber but the post can be attached using a 350mm nut and bolt assembly. Just keep in mind that all the weight and stress will be on those bolts when you start putting together the tree house over it.
One more way to join them is to use flat bracket plates. The only thing I'm not too keen on about this method is the number of holes you'll be drilling into the timber. It will save you from having to cut the timber, but there will be as twice as many holes to attach the nut and bolt assembly to the timber.
Let me call on our experienced members @Adam_W, @diy_hausdesigns, @ProjectPete, @Nham, @LePallet, @woodenwookie, @tom_builds and @Yorky88 for their recommendations on how to put your timber base together.
I've placed a sample sketch of how you might put it together. Please let me know what you think.
Please keep us updated with your progress, we look forward to seeing the start of your tree house project.
If you need further assistance, please let us know.
Eric
Thanks for tag @EricL and hello @mjkworldwide . I built this elevated tree house many years, not fancy but the kids had a great time. The posts are in the ground and cement was used to set them in place. I am not sure about the free-standing design but to be safe I would probably fix the structure to the tree. The alternative is to move the tree house to another location away from the roots.
Thanks so much Eric - very helpful. The lap joint looks very good.
As a more simple solution - if I was to butt joint the frame and then install the post in the resulting corner with bolts - would this be strong enough to handle the lateral loads? (Ie no lap joints)
A trial corner shown below..
Hello @mjkworldwide
Thank you very much for posting that update of your build. It's great to see that you've used a nut and bolt assembly, I would still recommend using an overlapping knee brace at the top and bottom to help stiffen the overall frame. I see you've done a diagonal installation of the nut and bolt, this is an excellent method of bracing the timber pieces together.
If you have any other questions we can help with, please let us know.
Eric
Thanks Eric!
Struggling to quite understand the orientation of the knee brace. When you say overlapping - so you mean in this direction?
Hi @mjkworldwide,
I'd suggest one of the two orientations I've rendered below. In your drawing, there is only a limited amount of space to put the brace, which forces it into a steep angle. With my proposed solution, you can use a much longer brace at a shallower angle, providing significantly more support.
Please let me know if you have any questions.
Mitchell
Through bolts will provide more rigidity, but I think you'll be fine with coach bolts @mjkworldwide.
In my opinion, you are already overengineering the structure, even considering it's free-standing and not concreted in. Your structure is wider than it is tall, so it's not going anywhere. As long as the joints are secure, you'll have a substantial structure. However, I'm all for going the extra mile, ensuring that any elevated structure children play on is safe.
Mitchell
