Professional treehouse builder and author Pete Nelson created this gem in Puget Sound, Washington, which, like the Tardis, seems to be bigger inside than it looks from outside.
This is home for a family of five! Sure, three of the residents are children, but it just goes to show just how open the possibilities are for living in trees in hyper space-efficient ways.
Here we have a relatively small home that uses space so efficiently that the whole family can live in it. Some windows are reclaimed and others are handmade. The wood is reclaimed cedar. The way these materials have been assembled shows that treehouse living can be done with elegance and style without spending scads of cash, and without taxing the planet by using a lot of new materials.
Nelson strikes a great balance between the organic forms, such as his striking use of stone along the base and the branches in the deck railing, and the human-made lines of the roof and windows. The stone gives it an ironic grounding quality despite it being up in a tree. This is a great reminder that you can incorporate a wide variety of materials beyond just wood into your design.