Tree House Build

So the kids wanted a tree house, this is what they got.
I know, not exactly a tree house, but its sitting around 200+ year old oaks, and I really didn't feel confident in injuring them at all.  So perhaps elevated playhouse is a better name.  In any effect, here is my build.

I started by clearing the area with my tractor and digging 4 foot post holes, one was only 3 foot when I hit bed rock.  
I put in 8 inch tubes and filled them with cement.  I put a 3/4 lag in the top of each to tie to.

Next I put a post plate on each for a 6x6.
Everything went together good here and the measuring and cross corner checking when I dug the holes really paid off, the entire thing was very square.  Next, I set 2x12 beams (2 on each) on the top of the posts.  I notched the posts to make it super solid and used 3/4 inch lags to hold them together.
From there I was able to build the joists that would be the floor of the playhouse.  I used 14 foot 2x8 with a 3 foot cantilever on all sides.
The top of the deck is now 6 foot off the ground for scale.  Next I decked the front 4 feet for porch and put sheeting down in the back half for the house.  I used all green treated lumber to this point I should mention.  Even the sheeting, which is extremely heavy (3/4 inch 4x8 green treated).
So then I framed up my walls all the way around with openings for the door only.  I didn't have windows to begin so didn't bother framing them in at this point.  I will cut and frame them in as I get them so I have more options for finding used windows.

So next I framed up a loft on the back 60 inches of the house using 2x6 boards.  I doubled up the 2x6 on the front to make a beam that could support the loft.  I used joist hangers to put them all in.  After that I swung joists.

So at this point we have the skeleton and I started sheeting it.  I just used A11 grade siding plywood in 4x8 sheets with galvanized #8 nails.  The walls were all 6 foot 3 so I can walk in without hitting my head so the sheets hang down a bit.

Once that was all in place, I started sheeting the roof with half inch OSB.

This picture has the drip edge on already.  So the final step was putting the metal roof on.  We also put a railing up by pocket screwing 2x4 on the posts that hold the roof up and putting spindles in.  We had created a 2 level playset the year before and moved that to the other side of the tree and build a bridge with some short 2x8.  The entire thing is 14 x 12 with a 10 x 12 playhouse 4x12 deck, and 5x12 loft.  I still need to make a door, frame in windows, fur the edges, and stain the whole thing.  But I will follow that up later.