Tree House (or Fort) Construction

The following is a list of step I used in building a tree house or fort at least for this summer.  I took upon this endeavor because my son saw tree houses in some of his favorite cartoons.  I used the following sources for design and information:
1) Mike Swenson - friend who works with my wife
2) Makendo
3) Eztreehousplanse
4) Tree Houses and Play Houses

Step 1

Install and secure 4x4 post, clamp 2x6 support beam, mount to tree, add quick dry cement to post, mount beam to post.

Select an appropriate location

Mount 2x6 PT Beam to tree.  Use 8 in long 3/4 in diameter galvanized lag screw (thanks Nutty Co. in Derby, CT) and secure to tree.  Notice the oval cut in the wood.  This was done in order to allow for tree movement.    

Install 4x4 post.  Not surprisingly, I hit roots about 18 in, but I installed it in Quickcrete anyway.

Step 2

Install and secure 4x4 posts, clamp 2x6 support beams, add quick dry cement to posts, mount beams to post (level with step 1 beam).

Install two additional 4x4 posts for front support.  

Use two 6 in  long 1/2 in diameter lag bolts

Step 3

Install and secure 4x4 post, clamp 2x6 support beam, mount to tree, add quick dry cement to post, mount beam to post (level with step 1 and 2).

Level support beam to the first support beam connected to the tree.  Add second support beam.

My helper is installing a pilot to go through both support beams and 4x4.

Step 4

Install 2x6 outer perimeter joists, square off, install 4 inner 2x6 joists.

Set ten foot 2x6 joists spaced 18 in apart on top of support beams.  Use 3 in deck screws and mount front and rear floor joists to the cross joists. 

Connect floor joists to beams using rafter ties and galvanized nails.

Add another support beam and connect to the front side of the tree and a forth 4x4 post set in Quickcrete.  Because I was not able to dig very deep on any post (below 18 in), I installed a 4x4 brace to the front 4x4 posts.  

All joists were secured with joist hangers.

Step 5

Add more supports and build stairs.

Mounted a 2x4 brace with a 6 in 1/2 lag screw.

Constructed the stairs using 2x6 stringers (rails) and treads (steps) and 3 in deck screws. Used 1x4 support cleats nailed to the rails for additional support.

Step 6

Add the floor.

Have helper inspect the floor.

Used standard 5/4 deck boards connected to the floor with 2 1/2 in deck screws.

Step 6
Add the railing.

Added the guard rails using 3/8 in bolts mounted to the floor joists.  The balusters were mounted to the 2x4 rails using 2 in galvanized deck screws.  The 2x4 rails were mounted guard rail beams and to the each other with 3 in deck screws.

It's done for now.  At a later date I plan to install a 1x4 rail cap to the guard rail.

Addendum: Guard rail cap and more bracing...

Good luck for your own project. Below is list of tools used during the construction.

Tool List
Hammer
Circular saw
Table saw
Compound saw
Clamps
Two cordless drills/screw drivers
Level
Jig saw