Part One consists of preparation for your tree house, picking a tree that will support bracers, buying the materials, gathering together the right tools in order to complete the job, and beginning to mount the main supports.
Beginning with the tree, you will need a tree that can hold the playhouse without structural problems. One way to do this is to choose a tree that has two to three trunks that touch at the base and splay out as they rise. Less bracing is required if you have a great situation of trees in your yard, if not no problem, although the bracing will have to be amped up a bit. Begin by thinking how high you want your treehouse. Nine to ten feet is usually perfect as it is still exciting for kids but not too scary.
The shopping list for materials to complete this project will cost around $250-$300 and will include:
Nails, deck screws, and pulley for 1/4″ rope.
3 x 10′ lengths of 2 x 4 PT lumber.
6 x 12′ lengths of 1 x 6 PT decking material.
2 x 10′ lengths of 2 x 10 pressure treated (PT) lumber.
6 x 8′ lengths of 2 x 6 PT lumber.
1 x 8″ long, 1/2″ diameter galvanized lag screw and washer.
8 galvanized joist hangers.
4 x 6″ long, 1/2″ diameter galvanized lag screws and washers.
8 galvanized rafter ties.
This is a big step, and one of the most important, as it will keep the whole tree house structurally safe. Begin with a light piece of wood and proceed to nail the end about one foot lower than you want the floor of your treehouse, use a level to achieve a true horizontal span and nail the other end to the tree.
Now drill 3/8″ holes in the tree directly above the strip of wood. Repeat on each side of the trees, using extra precaution the strips should be horizontal and level with the beginning strip on the other side of the tree.
The strips can be removed and the holes measured for the distance that is in between each.
Once this is done you subtract the distance from ten feet and halve the remainder. This formula is what you use to measure and mark this distance away from one end of your 2 x 10. Proceed in drilling a 5/8″ hole in the middle of the board, make a mark using your ”between the holes measurement”. Finally, Drill two 5/8″ holes on either side of your mark both of which should be in the middle of the board.
Time to get the handy Makita 4350FCT Top Handle Jig Saw out, make two cuts between the holes, making a 4″ long slot. Now you need to repeat this on the other side of the tree. Making this slot will allow the trees to move in case of windy weather saving your treehouse from tearing apart. Note: the more your trees move, the longer the slot ought to be.
Your boards can be screwed to the tree with a wrench and using washers, but be careful not to bolt too hard against the tree. For a long lasting tree house, perch the support away from the tree and use substantial lag screws.