My original sketch of how the tree house would look
I started building this "low budget, high quality" tree house in August of 2005. We have some forest land in central Wisconsin. In a forest, the trees often grow close together. They grow tall competing for the sun. Most branches and leaves are high at the tops. So, we do not have the thick wide lower branches that most tree houses are built on.
To solve this problem, I decided to use two trees to support our tree house. The trees I picked are oaks about seven feet apart. I first attached 2 twleve foot long treated 2x6's using lag long screws. I built a floor frame from 2x4's with outside measurements of 96 1/4 by 65 3/4 inches. This size was chosen to fit the lumber that I had available.
I assembled two strut support assemblies from a piece of 2 x 12 and some angle cut 2x4's. One assembly was attached to each tree with a single screw. An additional single 2x4 strut was attached to the outside center of both 2 x 6's with joist hangers.
UPDATE: The 2x12 backboards on the strut assemblies were cracking. So I made new backboards by screwing and gluing 3 layers of plywood together. The new design was much stronger due to woodgrain in many directions. I cut off the bottom corners so nobody gets poked.
NEW STRUT ASSEMBLY
I screwed down 5/8 inch plywood for the floor. I attached a treated 4 x 4 between the trees, 6 1/2 feet above the floor, with a single screw at each end. This 4 x 4 controls the sway of the trees and also keeps the house from tipping. The 4 x 4 goes through holes in the walls and is not attached the treehouse. When the window blows the 4 x 4 goes side to side freely.
September 2005 - Framing of walls is progressing. My cordless drill is getting quite a workout. Pressure treated wood is now in place for front porch. I found the Window at a neighbor's house that was remodeling.
I'm now designing the roof. The tree house will have a second level that extends above the front porch. I want to make a gambrel or barn shaped roof so the upper level will have more headroom. We have some partial sheets of leftover steel roofing from the garage the we put in last year. I think it is Grandrib 3 manufactured by Fabral. The sheets have ribs on 9 inch centers, so the roof peeks must be at multiples of 9 inch because the steel will bend at the ribs. Steel roofing is light weight and long lasting, perfect for a tree house.
To get all the angles, I divided the roof into triangles and used Ruby Scarab's triangle calculator.
Nice view of the roof ribs. The kids have already moved in.
November 2005 - We just put in the upper floor. I used a cool construction sign with a glossy coat and lettering on top with a 22 inch trap door cut in for ladder access. Working on the roof. I cut the rafters from 2 x 4's connected together with brackets made of plywood to form the "ribs" of the roof. The ribs are attached to the top of the walls with steel angle brackets. There is a 1.5 inch overhang on each side. Temporarily, we screwed a few 2 x 4's to stabilize the ribs until we can intall the steel roofing panels.
It's getting colder now, so I'm wrapping things up for the winter in nice big tarp.