Building Railings

A railing is primarily a safety device. All too often, amateur and even professional designers (especially professional designers) see railings as an opportunity to get creative. The result is an unsuitable railing, which is essentially useless. Build a strong, solid railing with closely spaced balusters and you won’t have to worry about who uses the treehouse, whether it’s small children or tipsy adults. That means no ropes, no cables, and no twigs. Okay. Lecture over.

A good treehouse railing employs the basic construction details of a standard deck railing. Many treehouse railings are even simpler, eliminating features like the broad horizontal cap rail commonly found on house decks. The important thing is to adhere to the basic design requirements:

• Tops of railings must be at least 36" above the platform surface.

• Balusters (vertical spindles) may be spaced no more than 4" apart.

• Horizontal balusters are unsafe for children, who like to climb them.

• Railing posts (4 × 4 or larger lumber) may be spaced no more than 6 ft. apart and must be anchored to the platform frame, not the decking.

• Top and bottom rails should be installed on the inside faces of railing posts.

• Balusters should be fastened with screws; if nails are used, balusters must be on the inside of horizontal rails.

• All openings in railings—for access to the tree house platform—must have a safety railacross the top.

To build a simple railing, cut 4×4 support posts to extend from the bottom edge (or close to the edge) of the platform’s floor joists to 36" above the decking surface. Anchor the posts on the outside of the joists with pairs of 1/2" carriage bolts with washers. Install post at the ends of railing runs and every 6 ft. in between, and at both sides of access openings and stairways.

Cut 2 × 4 or 2 × 6 horizontal rails to span between the top ends of the posts. Fasten the rails to the inside faces of the posts with pairs of 3" deck screws. Continue the rail through access openings to create a safety barrier. Mark the baluster layout onto the outside faces of the rails, spacing the balusters no more than 4" apart. Cut 2×2 balusters to extend from the top of the rail down to the floor framing, overlapping the joists by at least 4". Fasten the balusters to the rails and joists with pairs of 2-1/2" deck screws driven into pilot holes at each end.