Estimate the platform timber, decking boards, railings, roof and fixings for a raised treehouse or play platform.
Enter the platform width and depth, a railing height if you want safety rails (leave blank for none), and whether the treehouse has a roof. The tool estimates the platform joists, the linear length of decking boards, four corner support posts, and the railing timber and roof sheathing where applicable.
| Element | Guide |
|---|---|
| Joist spacing | 16 in / 400 mm on-centre |
| Railing height | 36–42 in / 900–1100 mm |
| Baluster gap | < 4 in / 100 mm |
| Platform height | Keep low for young children |
A 2 m × 2 m platform with joists at 400 mm centres needs about 6 joists and roughly 14 rows of decking. A 1 m safety rail around all four sides adds about 8 m of top rail plus balusters (spindles) no more than 100 mm apart.
Tip: fix to the tree with a few large bolts rather than many screws, and leave room for the trunk to move and grow — never wrap straps tightly around a living tree.
For safety and to protect the tree, most modern designs support the platform on its own posts or a combination of posts and a small number of tree fixings, rather than bolting everything to the trunk.
For a child play platform, railings of around 0.9–1.0 m with narrow gaps (about 100 mm) help prevent falls. Adjust to suit the height of the platform.
Use pressure-treated structural timber for joists and posts, and decking-grade boards for the floor, all fixed with corrosion-resistant screws and bolts.
Use a few large treehouse attachment bolts rather than many screws, and leave gaps so the tree can move and grow. Never wrap straps tightly around the trunk.
For family use 1.5–2.5 m off the ground is common; lower is safer for young children. Always add sturdy railings, which this estimator includes.
