Code-Compliant Screwed Guardrail-Post Connections
Use these blocking and screwing details to secure guardrail posts to the deck frame.
The current best-practice method to secure guardrail posts to the deck frame is using tension tie hardware that locks the posts to the deck joists (see ‘Code-Compliant Guardrail Post Connections‘). In late July 2015 Simpson Strongtie published an Technical Bulletin showing 4 guard post blocking and screwing details that pass the 500 lb. concentrated load test called out in the ICC-ES AC273 criteria. The guardrail posts are attached to the deck frame using Simpson Strongtie’s SDWS Timber screws along with double joist blocks and 4×4 reinforcing blocks.
The details are similar to the ones I used in the “Site-Built Deck Railing“ article but are done entirely using screws – no bolts.
You’ll need to follow the drawings closely – they depict the SDWS screw length at each location as well as the dimension off the top or bottom edges of the joist rim. The screw positions through one edge of a post are offset by 1/2 in. from those on the 90 degree edge. So to ensure they don’t drive into each other make sure to orient the screws perfectly level.
Table 1 lists the quantity and length of the SDWS Timber screws needed for each post-to-frame configuration.