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I had a large tree in my yard cut down to about 8' above ground. It now has two stumps joined at the base. I am planning to build a treehouse for my kids around the stump with the weight being held by 1/2 inch threaded rods through the trees holding up 2x10s.

The stumps are about 20 inches in diameter. I am worried that it might not be long before the stumps will rot and be too weak to hold up the weight of the treehouse.

How long of a life can I expect from my treehouse? Is there anything I can do to increase the life?

I am planning on treating the top of the stumps with bora-care to deter bugs. Any other suggestions would be much appreciated.

closed as too broad by isherwood, mmathis, Daniel Griscom, Tyson, fixer1234 Jul 2 '18 at 9:28

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  • What species of tree? – Jim Stewart Jun 28 '18 at 19:31
  • It is a linden tree. – Innuo Jun 28 '18 at 19:43
  • So en.wikipedia.org/wiki/Tilia? – Jim Stewart Jun 28 '18 at 21:05
  • I have heard anecdotally (yes I did it myself) that cutting copper pipe into 6 inch pieces (3-4 per stump) then pounding them into the stumps. The old pressure treated lumber was treated with a mixture of copper, chromium and arsenic. Keep in mind that the pipe will make it extremely dangerous to remove the stumps with a chainsaw at a later date. – mikes Jun 28 '18 at 21:07
  • Will you be putting the floor of the treehouse on top of the cut ends or will the tree penetrate into the interior of the structure. – Jim Stewart Jun 28 '18 at 21:14
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There are too many factors here to give any sort of objective answer:

  • Local climate
  • Tree species
  • Tree health
  • Location conditions
  • Future weather, insects, etc.

Ultimately it comes down to your tolerance for risk. A stump of that diameter will remain structurally sound at its core for a number of years, within reason. I'd consider it robust enough to support a modest structure (say 4x6 feet, weighing at most a few hundred lbs.) for at least four. However, the outer edges will begin to decay first. I wouldn't rely on lag screws, for example, for load bearing. I'd be cutting notches into the top of the stump to carry beams, and relying on mechanical fasteners only for stability.

Check it every year for signs of instability. It'll be fairly apparent when it starts to get sketchy.

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Holding everything “up” is not the problem. The stump is taking the load in “parallel grain” direction so it will hold the tree house and half the neighborhood kids easily.

The problem is rotation. When everyone runs to one side of the tree house, you’ll have a lot of force wanting to rotate those 2x10’s. The weak link is going to be keeping the tree house from rotating, not holding it up. You might consider adding a diagonal brace under the tree house down to the tree stump.

When you drill holes for the bolts, that will allow water to enter at the structural connection...and that will cause dryrot...exactly where you don’t want it. I’d seal the hole with tar or wax to reduce moisture infiltration.

  • Water causes "dry" rot? :P – isherwood Jun 29 '18 at 13:13
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From my experience, the stump will outlast your kid's interest in the playhouse... Enjoy it now, it doesn't last as long as you want it to.

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