Lag screw question: [View all]
I've gotten a bee in my bonnet to get cookin' on a treehouse for the kiddo, the only measurable result of which so far has been the placement of a single 16-foot 2x12 in a monster tree. Which took me all day. 
The idea, next, is to put up a second parallel 2x12, upon which I'll start building a small deck (maybe 8x10) and then erect small walls and put on a roof. Hooray, treehouse! But I've got a bit of a dilemma.
One end of each 2x12 I plan to bolt right into the tree, the other end I'll hang from a second bolt via a wire rope sling. This is a grand plan and will account for any tree movement between the two ends (which are on different sections of trunk). I've got the wire rope end nicely installed and it's rock solid.
The "right into the tree" end, however, well I had some trouble. Mostly because I was on a ladder, and I didn't wiggle my auger bit around much, and I didn't have a lot of room to swing my pipe wrench... the long and the short is, the lag screw ain't all the way in. And it ain't going any further.
Now, before you tell me I need to take it out and start again, let me add that it's a 1.25" diameter lag screw, and it's 15 inches long. I did manage to get about 8 inches of thread buried in the tree with a three foot pipe wrench, and the 2x12 sits out at most 3 inches from the bark. I'm thinking I could put some pipe in place, like a washer, to keep the 2x12 from moving side to side. And I'm thinking 8 inches of 1.25" screw in wood is an awful lot of strength.
But I have no idea how much strength that actually represents, and whether it's really enough. Any engineers out there today? 
= new reply since forum marked as read