The key to building strong deck railings is to fasten guardrail posts in a way that resists the lever force exerted at the post base when someone leans against the top rail. How this is done depends on where a post will be attached to the deck frame, but here are some best practice guidelines:
- Space guardrail posts no further than 6 feet apart.
- Don’t notch wood posts around joists or beams. Use at least two 1/2-inch bolts (preferred) or lag screws to fasten the base of wood posts to the face of the joist.
- Use metal, deck-post tension ties and wood 2x blocking to counteract forces at post bottoms. See details below.
For more on building safe decks, see the JLC Field Guide.