We have a massive mango tree in our yard and want to put in a tree house! We definitely don't want to damage the tree though, as it is our best mango-producer on the property. Does anyone know of any safe, bolt-free treehouse designs (using ropes, etc to tie the platforms on)? It won't be a full "house", probably just three platforms with short rails and stairs in between.
The main thing is to not use anything that will interfere with the growth of the tree.
Bolts generally won't hurt, but they should be in a sliding interface that keeps the treehouse from binding the tree.
Paul mentioned in a podcast once that he likes to put one very large bolt in the tree and hang the whole structure from that. I like that idea because it minimizes the stress to the tree, and it eliminates the stress issues mentioned in the link.
When I was building a tree stand I had 3 very tall white cedar trees to use. Since they were in a cluster of other trees they had grown quite close to each other and were thin for their height and tended to sway a lot in the wind.
I don't like putting single pivot bolts through trees, they work the hole bigger over time, moisture works it's way in, rot soon follows.
We've all noticed that when a fence wire is up against a tree the tree grows right over it. I though I might use this. I like the idea of using a log as the main beams, they last much longer than cut lumber in the elements.
I hoisted an 8" log up to the right spot, then wrapped a chain around the tree, out over and under the log, then back around the tree. I pulled the chain together and slipped a bolt through 2 links.
The links of the chain dig in to about 1/3rd of the circumference around the tree but they're large and smooth enough that they don't cut in to the bark too much. It's been there for about 5 years and shows no signs of stressing the live tree.
In addition you're grabbing around the outside of the tree and the log, so you'll never have either one split from the stresses as you might when you bore a hole through the center. The chain is self tightening, just by the weight of the log and anything you put on it.
I'm hoping over the years the tree will grow right over the chain.
There a lot of peace of mind with this design. You never have to worry about inspecting the attachment points that hold everything else up. Most of the log or tree would have to rot away before any kind of failure could occur, assuming your chain is of adequate size. You don't need that much chain either so go ahead and overkill on size if it makes you feel better.
This pic should make things clear(er).
A tree slowly pushes up against fence wire and envelops it. A wire placed against the bark and loaded with weight, will cut in and choke off water flow. Even if it doesn't cut, it could still squeeze the cambium enough to prevent it from working.