For the past 5 years since we moved to a new house the kids have been bugging me to make them a tree house. Naturally I waited until record lumber prices to begin the project! Our house sits on a hillside at the top of a hill with many mature Douglas Fir Trees. For the foundation of the tree house I selected a very large tree off of our deck. I used TAB brackets to support the back side of the platform and supported the front side with 6x6 posts. 
The original plan was a 14x14 foot platform with a 10x10 tree house, but all the lumber came in 16-foot so I decided to expand. Scope creep became the theme of the project!
With the platform framed we placed salvaged pressure-treated decking to make a walkway. I used strips of roofing felt over each joist to help to protect the joists. The The kids helped, making my wife nervous.
As we built we got to see lots of visitors.
Once the decking/walkways were done I fired up the floor where the tree house will be with 3/4 inch strips, then used 3/4" plywood to form the floor.
The plan for the tree house was a simple shed roof structure based around salvaged windows and a sliding glass door. I went with standard 16-inch spaced 2x4 studs, and T111 siding. It had been a decade or so since I had framed anything, but I bought myself a good compound miter saw and jumped in.
Around this time I got lazy in my picture taking. I framed each wall starting with the short one, then the angled walls and finally the tall front wall. I pre-painted the siding before cutting and attaching it to save time and mess later. I also built the bridge over to the existing deck so I could more easily transport materials over to the building once the walls were up.
Once it was dried in with the roof on it I relented to my wife's concerns and put up the railing. It's a good 15-foot drop off the tall side, so it really needed a railing. I matched the existing deck railing that used 2x2 posts and two 2x4s in an L shape for the top rail, but adjusted the post spacing to 4" to meet code. After that was trim (also pre-painted) and furnishing the inside. Here are some glamor shots I took over the weekend.
My favorite feature is the hanging egg chair. A few years ago my daugher drew a picture of her reading in a chair similar to this one, and I knew I had to find one to finish off this project.
The last piece is running some power over to it so we can have a light. I am still undecided about finishing the interior, but if I do that will be a next-year project. I would use some sort of wood paneling to save weight over drywall.
Overall I'm very happy with how it turned out, despite blowing my budget!
