Options for Fastening Deck Guardrails

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A deck guard system of rails and balusters or other infill relies on the underlying deck framing and 4×4 wood guardrail posts whether guardrail system is site-built or a manufactured system.  Testing done by the VA Tech in the early 2000s showed that common ways deck builders used to fasten the guard posts to the deck frame weren’t secure enough to meet the code-required load plus a safety factor.  Whether the posts were screwed, blocked or bolted (or combination of methods) to the joists and/or rim board – the post connections or deck frame failed.   The examiners did find that when the posts were reinforced to the deck frame using metal hardware that transferred the load back into the deck joists, the posts could handle the load without deflecting beyond the code limit.

A guardrail post is a long lever with the fulcrum at the bottom.   The small force at the top of the post translates into a tremendous force at top of the rim board or end joist.  From the original few post to frame connection details developed at VA Tech, numerous combinations have arisen all using the same principles – reinforce the deck framing or the post itself right where the post meets the deck frame.  And the original bracketed connection idea has expanded to block and screw connections that accomplish the same thing – reinforcing the deck frame where the post is mounted.

The complexity of the details vary depending on whether the posts are installed inside the rim board and end joists of the deck or on the outside.  The video shows over a dozen different post to frame arrangements.  From those you can probably extrapolate to other details that you’ll encounter on a deck like inside corners and clipped / diagonal corners.

Articles / Videos

• Guardrail Posts
• Code-Compliant Screwed Guardrail-Post Connections
• Code-Compliant Guardrail-Post Connections
• Start Your Railing Right

MiTek / USP Product Information

• Deck Tie Back

Simson Strong-Tie Product information

• DTT Deck Tension Tie
• Guard Post, Guard Rail and Baluster Installations Using Strong-Drive® Structural Fasteners© 2018 Simpson Strong-Tie Company Inc. T-F-GRDPSTRL18
• Code-Compliant Guardrail Post Connections
• Deck Connection and Fastening Guide