Here are some ideal trees for your treehouse project: • Maple • Oak • Beech • Hemlock • Sycamore • Pine • Fir Some trees are more suitable for a treehouse than others. An arborist or local contractor can help you choose the best tree. You want a healthy tree with a trunk that has a diameter greater than 12 inches. Some of the best trees are deciduous trees and nut trees.  Avoid building a treehouse on soft trees, like the poplar or willow.