A Sample Project from the Appendix: Treehouse

The main consideration with a tree house is that it should be safe. A square collar of 4-by-4s around the trunk of a generous, sturdy tree can be supported by large posts set into concrete bases. Rather than dig holes for concrete right next to the tree trunk, which would involve cutting roots, build square boxes 2 feet (.6 m) on a side and 2 feet deep, place a flat stone in the bottom of each box and set a post upright on it, then fill the boxes with concrete. When the concrete sets, remove the concrete from the wooden boxes and set them around the tree so their posts support the square collar on top.

The collar then becomes a foundation for angled supports for the platform in the tree, avoiding the need for nailing wood to the tree. On the platform, build sides and a roof if you want to make an actual all-weather tree house. Make sure the ladder is safe--a rope ladder is good exercise, it’s safe, and the kids can pull it up so marauding pirates can’t climb into their redoubt. Keep the platform, and thus the length of the ladder, to no more than 6 to 8 feet (1.8—2.4 m) above the ground, and install a soft safety surface where kids will land if they fall. Rises higher than 8 feet may require a check of local building codes and will become precarious indeed, unless secure and sturdy stairs with a handrail leading up to the house are constructed.

If the tree house is elaborate and heavy, make sure that the limbs on which it rests are strong, with wide crotches and no rot. Use additional supporting posts under the corners of the platform so that the entire load doesn’t rest on the tree or the support collar mentioned above.