In the yard, there were three trees that would have worked for the fort with the design chosen, but the one in the back yard seemed the best. Being somewhat hidden from outsiders, it provides a private domain for playing. The tree is a Red Pine with a 20" diameter at 5' up. Ideally, I would have liked to have two massive and healthy hardwood trees in the back yard on level ground with perfectly straight trunks and a 8' space between them. I suppose that the pine will do.

For starters, the supports and floor were installed. I put up the parts by myself with the help of pulleys and lots of rope. Remembering high school physics came in handy.

The floor of the fort is made from A2C 2X4 and 3/4" A2C plywood. It was mostly assembled on the ground, and then lifted up on the supports. As a general rule of thumb, 8' of A2C 2X4 weighs 12#, and 4X8 sheets of plywood weigh 25# per 1/4". All together, the floor weighs about 200#.

Next comes the walls. They were pretty easy to build, and my son enjoyed helping out periodically in constructing them. his favorite part of building the walls was painting them.

After the walls were built and put into position, work began on the roof. For the roof, I was completely 'off script' for directions. I started with prefabricated sections, but they proved too difficult to manage; halfway through building the roof, I switched to stick-based construction, which worked much better.

There is an interesting detail in the following pictures; if you look at where the floor meets the walls, you can see a couple of 2 foot long scraps of 2X3 attached to the floor. These were used to allow me to push the walls out to the edge of the floor without risk of pushing the walls off the platform while positioning the walls.

Below is a pic of the stick-based construction of roof. I used asphalt roofing panels because I like the look. However, they do seem touchy to bad swings of the hammer.

The following picture shows the completed roof and the trim work for the windows. The trim work will need to be touched in the corners and the screw holes, but from a distance, it seems to look OK. This picture also shows that the base and floor have been painted. The wood seemed dry enough, so I put on some latex primer and then a coat of paint. By the time it needs repainting, maybe my son will want to do it...

Here we see a good shot of the ladder. The steps are A2C 2X3, and the rails are A2C 2X4. The way in which the ladder is attached to the fort is interesting. (I'll have to add a picture of that to the site.)

The following picture is of the work site. On the weekend afternoon that this was taken, the temp was around 95 degrees, The lawn chain with the cooler next to it came in handy for the breaks. I have found that adding some water to the ice in the cooler makes the drinks colder because it improves conductivity of heat by increasing surface area, and given the ratio of energy needed for phase change from ice to water to temp change of water, the result is an afternoon of ice cold (32 degrees) beverages.

There was some question of how level the fort was. Through a combination of bad photography and having the supports set at angles in order to have the floor level, it tends to look worse than it is. Using a level, some research into the meaning of the hash marks on the level, and some guesswork, each side appears to be off by about three degrees. (Which I can live with given that it is built in a tree and by an amateur builder.)

...

The main remaining tasks are to construct a door frame and a door, and to build windows for the fort. These tasks proceeded at a slower pace than construction had been moving because the fort became usable, and I had neglected other projects during the summer...

It took a few weeks to build the windows and doors. The following pictures show their progression.

The windows all turned out nice, but the following is my favorite window because it hinges from both sides and opens in the middle. One thing that I really like about this window is that I built it not knowing exactly how it was going to work such that it could properly close and latch. (There was something exciting about the challenge.)

Here is another picture of the same window from the outside.

After the windows, came the door. The process of making the door was quite similar to the windows. It just differed in size, shape, and plywood in place of plexiglass. Here is the door being glued together.

After getting it glued together, the stain and spar urethane were added. After that, the door looked like the following.

After adding a door knob and attaching the door to the door frame, then it was just a simple matter of adding carpet, and then it was done. The finished product is shown in the following videos. The first one is a tour of the tree fort, and the second is a walk-around of the tree fort.

For those in China, the "treefort tour" video can be seen at http://www.56.com/u71/v_NzI0ODUyMjA.html , and the "treefort walk-around" video can be seen at http://www.56.com/u43/v_NzI0ODU2MzI.html .