Everybody's Treehouse

When Bill Allen builds treehouses, he does not look for the perfect tree, sturdy with thick, embracing limbs and an abundant canopy of leaves. Mr. Allen's nonprofit company, Forever Young Treehouses in Burlington, Vt., founded in 2002, designs its houses to be accessible to handicapped and chronically ill children, and “the first thing we look for is the grounddropping away” from the start of the access ramp, he said, so that the ramp doesn't need to climb too high to reach the house. He also likes to build in a grove of trees so the ramp can meander from tree to tree. Everybody's Treehouse, which cost $450,000 and which Mr. Allen completed in January in the Mount Airy Forest park in Cincinnati, is a typical Forever Young project. Its 160-foot ramp winds among 14 trees (red and white oaks, maples and ash) as it climbs 15 feet to a 2,000-square-foot house with two asymmetrical cedar-shingle roofs that give it a Hansel-and-Gretel look. The structure is made of tongue-and-groove pine boards with an ipê-wood deck and has eight windows; most start 32 inches from the floor, an ideal height for wheelchair occupants. “For a kid in a wheelchair,” Mr. Allen said, “it gives a different perspective of what the world looks like, of what a tree looks like, of what a forest looks like."