Setting out to build a treehouse can be either relatively easy, or quite difficult, depending on the complexity of the desired treehouse. To build a treehouse for a child, one needs only a bit of lumber, some nails, a hammer, and a suitable tree. To build a treehouse that can actually be lived in for a long period of time requires a great deal of careful planning, strong timbers, one or more sturdy trees, and possibly building permits.
The most simple sort of treehouse you can build is simple a few planks of wood that make a platform in the tree, connected to the ground by a rope ladder or struts of wood along the trunk of the tree to climb. To build a treehouse of this sort you need only make sure to find a tree that is healthy, with no loose limbs or rot apparent. Lengths of two-by-four cut to whatever size you want the platform can be attached straight to a thick branch of the tree, and for added safety you can add bottom struts that connect to the trunk, or ropes that connect to higher thick branches. A simple ladder connects the platform to the ground, and a rope ladder will allow the inhabitants to seal themselves off from disturbance. Of course, without railings or walls, such treehouses are really only intended for older children, as they can present a risk of falling.
To build a treehouse with a bit more substance, you’ll start out in much the same way. Locate a sturdy, healthy tree, and find a clear area a ways up the trunk. Build a sturdy platform, either connected to a strong central branch, or built off of the trunk itself. This platform should definitely have a number of diagonal braces connecting it to the trunk at various points. The platform ideally will be connected to the trunk by ropes, reducing harm to the tree, but if ropes are not feasible, galvanized screws should be used in place of ungalvanized nails, as they will cause less harm to the tree and minimize the chances of it dying.
This base platform will act much like a foundation of a house, and the next step will be adding a floor. To build a treehouse that looks and feels more like a real house, you’ll want to use real floorboards, or even hardwoods. Once the floor is on you will erect the walls, which for larger houses should be constructed on the ground and then lifted up into place and attached. The roof is often put on up in the tree, especially when you want to build a treehouse in which parts of the tree come in through the roof, as you will need to very precisely build the roof around these branches to ensure a tight seal.
After the frame of the treehouse has been built, you can add any number of trim items. Doors, windows, decks, railings, staircases, ladders, and even internal appliances, plumbing, and electricity can all be added. The sky is the limit when building a treehouse, and some people have built multi-room treehouses with multiple stories, and exotic touches. Make sure to check your local building codes, however, to see what permits may be required to build anything more than the simplest non-habitable structures.