Normally, I like to hang stair stringers from the rim joist using metal straps, but it’s helpful to have different attachment methods for different situations. Recently, I settled on a solution that looks good, isn’t dependent on metal hardware, and satisfies my building inspector. Because the 2×10 PT lumber we typically use for joists and rims doesn’t offer sufficient attachment for stringers, the detail incorporates a 2×12 into the rim joist where the stairs are located.

Instead of placing the 2×12 on the outside of our standard double-2×10 rim joist, I add it to the inside. That way, the bottom edge of the 2×12 isn’t exposed once the rim is wrapped with PVC trim. Another advantage is that I can build up the tripled assembly using 2×12 offcuts left from cutting the stringers. A continuous 2×12 is preferable, but my inspector is happy as long as the sections are longer than 2 feet and are securely attached to the rim joist with structural screws. And I’m happy to keep the offcuts out of the landfill.

When notching the stringers, I extend the top tread length by 3 inches (more or less, depending on the actual lumber thickness), then notch as needed to maintain the correct riser height. Finally, I drive structural screws through the back of the dropped 2×12 into the stringers to make a solid connection.