Most treehouse builders aim to use a small number of large bolts (or custom fasteners) to attach supports to the tree, for reasons of tree health
. These are not normally available in hardware stores but you can order them online. Please add any suppliers you have found that are not on this list, or comment on your experience with any of these suppliers.Treehouse-specific suppliers
These companies build treehouses and have developed their own special hardware. These parts are designed with high loads in mind and are the ideal choice, but come with a higher price than standard components.