Strong Rail-Post Connections for Wooden Decks - Images 8-14

The authors first tested two post connections found commonly in their area, one where the 4x4 pressure-treated post is notched and lag-screwed to the band joist (top detail), and a second where the post is through-bolted to the deck band joist (bottom detail). Code requires that a rail post be able to withstand a 200-pound force applied in any direction. The researchers tested the worse-case scenario only, by pulling outward at the top of the post; they applied a 2.5-times safety factor, according to code-accepted test protocol.

After testing the bolted and lagged connections, the authors tried reinforcing the post with blocking in a variety of configurations. Each configuration they tried failed when the blocking split along the grain.

A Simpson Strong-Tie HD2A, installed sideways on a joist, proved able to resist the torque at the base of the post. This connection detail requires that the post be installed at a deck joist.

The authors tested the HD2A connection with the post installed both inside and outside the band joist; both configurations withstood the full test load. At 200 pounds, the sample post shown above deflected but the connection held; at 650 pounds, with the post still holding, the test was ended so as not to damage the test machine.

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