In this first phase, the objective is to get the main supports in place, and enough of a framework for the floor that I can work up there.
|Here you see the tree from the east (with a neighboring tree casting a dark shadow on it). I have
fixed the first support in place. This is a 10-ft. 2×6 beam running north-south.* You are looking at it from
the east, so south is at the left of the picture, north at the right.
This beam will support the north-south diagonal of the square floor.
The beam is about 14 feet up. The floor of the completed tree house will be at about 15 feet up, and about 7 feet square.
* Strictly speaking, northeast-southwest. I'm being a bit sloppy with these compass points.
|Here is another view of the first support beam. Note that it is bolted to the north fork of the
tree with a ¾-inch steel bolt going right through the tree. One fixture like this won't harm the tree; though
two such, close together, will cause the wood between them to degrade for lack of nourishment.
My beam is not fixed to the other, south, fork though. Trees move in the wind, and these two forks will move relative to each other. The distances they will move are small, but the forces are huge. Now, it is a basic fact of physics that a huge force remains a huge force, even if it only acts over a tiny distance.
In this case, if I were to bolt the beam to both forks, the forces involved when they move might be great enough to shear off a bolt, or cause serious damage to the tree. So the south end of this beam just rests in a secondary fork, and can move freely.
|Using that beam as a basic support, I now build the first, north-south, diagonal of my tree
house's floor. This is just another 10-ft. 2×6 set on top of the first one.
This view is from the west. Here you can clearly see how that first support rests freely in the secondary fork.
To insure vertical integrity, I have bolted the upper beam in place with eight pieces of 2×4 (two pieces on each side). Note that the lower bolts do not go through the first beam. Because that first beam is so important, and takes so much weight, I avoid compromising its structural integrity wherever possible. I especially avoid drilling holes through it. Those bottom four bolts just nick it.
Note also that this second beam is put up in two parts, with an 1½-inch gap between them. That's where the other, east-west, diagonal will go.
|Another view, from below to the east, of the completed north-south diagonal. Note the metal cuff on which the east-west diagonal will rest.|
|The second, east-west floor diagonal has been hoist into place, and supports are being added.
These supports — one on each side, east and west, to make a "Y" — just sit in hollows in the
crotch of the tree's main fork.
This is the trickiest part of the work so far, and possibly altogether. The east-west diagonal needs to be hoist up, then maneuvered into the slot I left in the north-south diagonal. There it just sits, balanced at its precise center, while I get the west arm of the "Y" into place.
(Though as you can make out, I put up some small brackets for slight additional support at the center. I also "anchored" each end of the beam — see following pictures — for a little extra security. Still, you need to keep your wits about you with 10-ft. beams wobbling about 15 ft. over your head; and civilians, especially children, should be absolutely excluded from the vicinity while this is going on.)
The east-west diagonal had two ¾-inch holes pre-drilled in it. The trick is to line up the west arm of the "Y" to get the location where a matching hole needs to be drilled, while simultaneously leveling the east-west diagonal with a spirit level.
Getting the beams in place, and adjusting the angle of the Y-supports, is all done with rope work. I didn't bother with pulleys for this; I find I can easily hoist up a 10-ft. 2×6 by hand. You need decent pitching skills, though, to lob a stone, with one end of the rope tied round it, through a suitable supporting fork 20 feet up. You also need to be nimble at getting out of the way when that sucker misses, bounces off the tree, and comes back down at you. (You also need a decent pair of leather gloves for the rope work, unless you enjoy getting rope burns.)
Notice how the east arm of the "Y," not yet bolted in place, is held in a rope "sling." When you are up there positioning, you can do fine adjustments by tugging on the string.
|Here are two examples of the "anchors" I mentioned in the previous frame. One is just a big rock,
the other an old tar bucket filled with bricks and stones.
Anything heavy like this will do as an anchor for your rope work, though you don't want to put too much angle on the bucket type, in case it tips over & discards its contents … which leads to a swift victory for the force of gravitation.
|Now both arms of the "Y" are bolted to the east-west floor diagonal. Their lower ends rest in
hollows at the main tree crotch.
I did some shaping of their ends to make a better fit. However, I anticipate some slight settling down there, so I deliberately shimmed up the east-west diagonal by a quarter inch or so when setting it in place.
The rope tied around the trunk above that main crotch is just a super-precaution, in case one of those Y-arms should jump out. I can't imagine why it should, but you never know. When everything's settled, I might bolt the lower ends of the Y-arms together, or fix them to the tree somehow — haven't really thought that out yet.
(Not sure what that is over at the right … But you know, I've had a funny feeling I was being watched …)
|With the two arms of the "Y" secured, I now have both of the floor-support diagonals in place, and
reasonable rigidity in the vertical plane.
I do not, however, have rigidity in the horizontal plane. That east-west diagonal swings slightly in the wind, moving the Y-arms with it. I therefore need to think about horizontal rigidity.
I make a start on this by fixing two pieces of wood (they are 2×4s, about 18 inches long) near the center, joining the north-south diagonal to the east-west one. You can just about make out one of these in this picture. At this point also, I square off the two diagonals, getting a good right angle at the center there.
Now, at last, I can start work on adding the sides of the square. In this picture you see two of the sides in place, the northwest and southwest sides.* These sides are also 10-ft. 2x6 beams. They are just drilled through and bolted at the corners with 6-inch galvanized bolts.
Notice how much bolting I'm doing, as opposed to nailing or screwing. There are trade-offs here. A bolt needs a bolt-hole to be drilled, degrading the structural strength of the wood. On the other hand, a bolt, when in place, won't go anywhere, which is not quite so true for nails (much less wood screws). And bolts have the advantage that you are making a kit out of the whole thing. Your structure, or parts of it, can easily be dis-assembled and re-arranged, if it proves to be unsatisfactory in some way — e.g. not as strong as you thought.
* Which I am henceforth going to refer to as "north" and "west" sides, for the sake of simplicity. I should really have started off by referring to the "north-south" diagonal as "the northeast-southwest" diagonal … but I didn't.
|All four sides of the floor base are now in place, bolted to the diagonals at the corners.
In theory I can now lay down flooring. Actually there are a few things to do first, notably locate a place for the access trapdoor. Still, this feels like the end of Phase 1.
|I now have enough of a structure in place that I can go and work up there. This is a relief. I
don't mind heights, but I never feel happy working on a ladder, especially a cheap collapsible (eek!) aluminum ladder
of the kind I have been using here.
It has the further advantage that as I am working up aloft I can see what parts of the structure shift, what parts settle, what parts groan. Then I can make necessary adjustments and enhancements.
End of Phase 1.
Continue to Phase 2.