In this post, the last in a series of six, we will discuss how to build code-compliant stairs for your deck. When constructing a deck, ensuring that stair stringers and treads are properly connected is crucial for safety and compliance with building codes. Here are some key considerations for stair dimensions and connections:

Stringers: Use solid 2×12 wood members or similarly sized preservative-treated lumber. The maximum horizontal span for a cut stringer is 6 feet, while a solid stringer can span a maximum distance of 13’-3”. Stringers should be spaced no more than 18″ apart, though 12″ is recommended by NADRA. Provide solid blocking at the posts between stringers for added stability.

Stair Dimensions: The stairway width should be at least 36″. If railing posts are inboard, measure inside the clear width of the posts. Stair riser height should not exceed 7″ (NADRA/IRC) or 7 3/4″ (DCA 6). Stair tread depth should be at least 11″ (NADRA/IRC) or 10″ (DCA 6). Open risers are allowed, but gaps must be less than 4″.

Landings: A solid-surface landing, such as concrete or pavers, is required for a length of 36″ from the nose of the bottom tread.

Footings: Footings must meet the same requirements as the deck if attached to the home, or a minimum of 12″ deep if detached.

Loading Requirements: Stairs must support a minimum load of 40 psf, and individual treads must support a 300 lb. concentrated load.

Guardrails: Stair guardrails are required for stairs with a total rise of 30″ or more, with posts spaced no more than 6′ apart and a height of 34″. Handrails must be continuous for the full height of the stair flight. The gap below the bottom baluster and the tread has to be smaller than a 6″-diameter sphere. The gap between the balusters has to be smaller than 4″.

Additional Considerations

• Rim Joist at the Top of Stairs

With the minimum 2×12 rim depth at the stairs and the minimum rim joist requirement being only 2×10, you will need an additional member to be added below the standard deck rim joist.

One recommended solution is adding a minimum 2×8 header below the already placed 2×10 standard rim. This additional depth is often necessary because a standard rise is approximately 7″, which means you need extra depth to fasten your code-required metal connector to attach your stringer, such as the LSC adjustable stair stringer. Fasten this to the post with Strong-Drive® SDWS™ Timber screws and a DJT14 joist-bearing post cap to take the bearing load.

• Bolt a 2x Wood Member to the Concrete Footing at the Base

To secure the landing footing that will terminate your stringers, use mechanical anchors or epoxied anchors to attach this pressure-treated 2x cleat to the landing footing.

Hangers for Stringers to the Header/Rim Joist

Building codes require that the connection to the header/rim joist be made with a steel connector and proper wood screws. The LSC adjustable stair stringer is a suitable choice for this connection.

• Post Connection

Railing posts need to withstand a minimum deck railing load of 200 lb. in any direction. To ensure this, connect the base not only with your post base with a 1″ standoff but also back to the stringers and outer rim using a tension tie like the DTT2Z.

Simpson Connector Products

Simpson Strong-Tie offers a range of solutions to ensure your deck stairs are securely connected and compliant with building codes. Refer to our Deck Connection and Fastening Guide for additional information.

• LSC Adjustable Stair Stringer Connector: Field slopeable to almost any angle, ideal for attaching the staircase stringer to the deck. Suitable for solid and cut stringers. Stainless steel or ZMAX® coating is recommended for corrosion resistance.
• TA Tread Angle: Provides a positive connection, eliminating the need to cut or notch the stringer. A full-width stringer is stronger and helps meet maximum guardrail opening requirements.
• ABU or ABW Post Base: Adjustable post base with a 1″ standoff for the post-to-footing connection and added stability at the landing.
• DTT2Z: Used to resist lateral loads at the base of the stair railing post by fastening back to the face of the bottom riser.

Post-installed anchor products allow you to anchor deck stairs after the concrete has cured. Options include the following:

• Drill and Epoxy: SET-3G® or AT-3G™ anchoring adhesive is placed in the drilled and cleaned hole, and a straight threaded anchor is adhered into the footing.
• Titen HD®: A mechanical anchor available in either in stainless steel or in mechanically galvanized carbon steel is another strong, corrosion-resistant option for securing deck connections to concrete.

By following these guidelines and using the appropriate connectors and fasteners, you can ensure that your deck stairs are safe, sturdy, and built to last. Always check with your local building department to ensure compliance with local codes and regulations.

Blog Series Conclusion

In this series we have walked through and described in detail the key connections on a deck that homeowners, builders, and building officials should be aware of. These connections will help create a continuous load path where all your critical load-carrying members are attached together using the code-accepted connectors and fasteners.

Decks are sometimes perceived as simple structures, but they do need to be designed and built properly. It is one of our goals to help make decks enjoyable extensions of your home where you can relax with friends and family in the comfort of knowing you’re supported by a safe, properly built structure. Whether you’re designing a deck, building a deck, or performing an annual inspection of your existing deck, we hope that this series has provided greater awareness of what the building codes require for a safe, long-lasting deck.