The guardrail / deck connection is a critical element of deck design, but until relatively recently, the design of this important connection was left up to the whims of the contractor.  Why is this important?  When people gather on decks, they inevitably congregate along the guardrail, to enjoy the view, take some weight off, or maybe set their drink.  After some high profile guardrail failures, the building codes eventually stepped in to create a standard to help ensure that sturdy guardrails are the norm, not the exception.

Currently, guardrails (or guards as the code refers to them) are required to resist a single concentrated load of 200 pounds, applied in any direction at any point along the top.  A 200 pound load pushing outward on the top of  a 42 inch tall guardrail (the current minimum guard height) can overload many older methods of post attachment.  In tests performed by Virginia Tech University, such loads would rip the post and rim joist entirely off the deck framing.

So how do you prevent this from happening?  The easiest way is to use metal hardware, such as a Simpson DTT2 to ensure the post is well secured to the adjoining deck joists, and not just the rim joist.  Below is a sample detail from the Simpson Technical Bulletin on the issue.  Notice the hardware on the upper post connection.

Simpson Detail

If you are ever unsure about the integrity of the structural connections for your deck, it would be a good idea to have a deck inspection by a qualified inspector, or experienced deck contractor.  JMC Building Inspections owner Paul Barraza is a NADRA certified Master Deck Professional.  For more information and details on meeting the current guardrail standards, please check out Simpson’s Technical Bulletin on the subject.

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