Some treehouses are built with more than just fun and games in mind. "This one belongs to a great family with a special-needs daughter," says architect Warren Lloyd. "It occupies the loft level of the house, and the trunk conceals a residential lift that ensures the daughter has access to all parts of the house." He adds that many elements, like the branches nested under the deck, were the owners' ideas. The tree trunk was framed in wood, and the branches are a steel frame. Both were finished with epoxy resin and synthetic materials.