With the implementation of the 2015 IRC, contractors and designers should be aware of the expanded scope of Section R507 Exterior Decks. The additional discussion in this section of the code simplifies the prescriptive construction of exterior decks.
Over the last few revisions to The Code changes have placed emphasis on construction conditions that will reduce catastrophic collapses of exterior deck systems. These changes included the requirement for a hold-down or similar tension device. However the 2012 IRC only provided a prescriptive connection that required interior access to install (Figure 507.2.3, 2012 IRC).
While this detail is continued in the 2015 IRC (Figure 507.2.3(1), 2015 IRC), it is supplemented by Figure R507.2.3(2), which permits the use of a hold-down device installed only from the exterior of the building.
This connection can be made with products such as the Simpson Strong-Tie DTT1Z. The DTT will need to attached to the structural framing with a 3/8-in. diameter lag screw into at least 3 inches of solid wood framing (or other approved connection). The lag screw will require a pilot hole. Because the device is designed for tension-only, it does not need to contact the wall cladding. It can be installed at a spaced distance from common cladding such as brick veneer, fiber-cement siding, or even vinyl siding. The image below is a cut-away from Simpson Strong-Tie illustrating a typical installation.
