Building a deck for a treehouse project. Installed deck posts inside rim joists with blocking. Question: is it better to install the 2x4 top/bottom rails on the inside or the outside of the deck posts? I could see how installing inside is stronger but then you lose a bit of deck space.

1 Answer 1


If the rails have rotted to the point that proper hardware no longer holds them in place, being inside the posts won't offer much more security.

If you're going to install them inappropriately (i.e., nailing) the position would matter more.

For a railing that will be leaned against, something like carriage bolts, fender washers, lockwashers, and nuts would be a version of "proper hardware." Purpose-made brackets would also be a version.

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