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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!!
@MitchellMc and @EricL - thanks for all your help so far. Project is progressing well and I have another question!
I have notched the 150x150 posts so the outside beams will sit on the posts . The remaining notch is 100x100. I was intending to through bolt the two beams onto the post as per the sketch. My question is - would 4x bolts be too many in this crowded space? Will it weaken the join? If not -what is the best layout for the bolts. Staggered or ok to have them in the centre? I assume most of the load is being transferred down the post so maybe not so important..
Thanks!
Your assessment is correct, the weight of the beams has now been transferred onto the post which is the ideal method to put this together. This is so that the bolts will not be carrying any weight. Their purpose is now to keep the beams in place and deal with the lateral forces applied to them. I definitely agree that you should offset the installation of the bolts to provide better bracing for the structure.
Since the forces applied to the post are downwards, it shouldn't compromise the overall structure of the post.
If you have any other questions we can help with, please let us know.
Eric
In order for us to get a better idea of what kind of timber it is, I would probably need to ask you to sand down one full side of the post in order for us to identify its timber pattern. In its current state, it's very difficult to identify. If you haven't had a difficult time cutting and drilling into the timber we can make an educated guess that it is not aged hardwood. If it was, it would be like cutting and drilling into steel.
Eric
Thanks @EricL
I’m not using particularly powerful tools however it does seem like a fair slog to saw and drill through it. It also has a very fragrant scent when cut. Cedar perhaps?
I now have most of the structure up and was hoping for a bit of advice on floor joists for the decking. I intend to have 4-5 joists supported from joist hangers along each side beam as per the sketch below. They will span 2.32m. What type of wood would you recommend and how deep should they be to support the decking above? I have 19mm spotted gum boards for the decking.
Thanks again for your ongoing support @EricL !
Hello @mjkworldwide
It's great to see that you've made progress with your build. If the span between the beams is more than 2 meters, I suggest using nothing smaller than 140 x 45. I recommend a spacing of 450mm between joists.
If you need further assistance, please let us know.
Eric
If you're deciding on which timber to use just make sure it has a rating of H3 so that it's rated for outside use and protected from moss, mould and insect attack. It's usually tagged for framing use.
Eric
Hi @EricL and @MitchellMc
The 'tree platform' build is progressing!
I did have a structural concern which I was hoping you might be able to get some advice on. I was happily drilling bolt holes through the side beams for the balustrade and didn't do my research on compromising the structural integrity of the beam. On further research google is unequivocal that you should NOT drill holes anywhere near the end of the beam where loads are likely to be greatest.
Do you think several 8mm holes with bolts will impact the structural integrity of the beam?
If so - would you recommend some bracing such as the last image?
Thanks so much for your ongoing advice!
