How to Measure Deck Stair Stringers

Deck stair stringers are a huge part of the structural integrity of any deck with stairs, providing support for each step and determining the stability and safety of the staircase. These long, notched boards act as the backbone of the stairs, holding up the treads (horizontal steps) and risers (vertical faces). We’ve written a full guide on how to measure for deck stairs, but we decided to put this resource together to go a bit deeper on how to create this crucial structural component.

Accurate measurement and cutting of stair stringers are crucial, as improper cuts can lead to uneven steps or even a compromised structure. Properly cut stringers ensure a safe, comfortable stair incline and a visually appealing finish, meaning careful planning and precision are vital to creating durable, reliable deck stairs.

Understanding Key Terminology

• Stair Stringer: The structural component of the staircase that supports the steps.
• Tread: The horizontal part of each step where users place their feet.
• Riser: The vertical part between treads, providing the height of each step.
• Total Rise and Run: Total rise is the full vertical height from the ground to the deck surface, while the total run is the horizontal distance the stairs will cover.

Tools and Materials Required

To cut deck stair stringers accurately, you’ll need a few essential tools and materials:

• Measuring Tools: A tape measure and framing square are essential for taking precise measurements and laying out accurate cuts. A level will help ensure the stringers are even when installed.
• Cutting Tools: A circular saw is ideal for making the main cuts, while a handsaw or jigsaw is useful for finishing corner cuts without overcutting.
• Safety Gear: Always wear safety glasses, hearing protection, and work gloves for protection during the cutting process.
• Materials: Use pressure-treated 2x12 lumber for the stringers.

Calculating Stair Dimensions

Accurate stair dimensions are key to ensuring safe, comfortable steps. Start by calculating the total rise, which is the vertical distance from the ground to the deck surface.

• Determine the Number of Steps: Divide the total rise by the ideal riser height (usually between 6 and 8 inches). Adjust as needed to ensure each riser is equal in height.
• Calculate Tread Depth: Typical tread depth is around 10 inches, but you can adjust this based on the desired stair angle and space available.
• Total Run Calculation: Multiply the number of treads by the depth to get the total run of the staircase.

Finally, always check local building codes, as some areas have specific requirements for riser height and tread depth. Compliance ensures not only safety but also that the stairs meet legal standards for residential structures.

Laying Out the Stringer

Laying out the stringer accurately is essential for ensuring that your steps are uniform and safe. Begin with a framing square, a tool designed to simplify this process. Set the framing square to your desired rise and run measurements (for example, 7 inches for the rise and 10 inches for the run).

• Mark the First Step: Place the square on the 2x12 lumber, aligning the rise and run measurements along the edge. Trace along the square to mark the first step.
• Repeat for Each Step: Move the square down and repeat the process, aligning each mark with the previous one to create a consistent stair pattern.
• Account for Tread Thickness: Adjust the bottom of the stringer by subtracting the thickness of the tread material to ensure the first step is level with the ground.

Precise layout is essential for smooth, secure stairs, so take your time to ensure each step is marked accurately.

Cutting the Stringer

Once the layout is complete, you can begin cutting the stringer. Use a circular saw for the main cuts, carefully following the lines to maintain accuracy.

• Finish the Corners: To avoid overcutting, leave a small uncut portion at each corner, then use a handsaw or jigsaw to complete these cuts. This method preserves the strength of the wood by preventing unnecessary cuts that could weaken the stringer.
• Check Each Cut: After cutting, inspect each step to ensure accuracy. Even small inaccuracies can cause stair instability, so double-check for clean, precise cuts before proceeding to installation.

Installing the Stringers

With your stringers cut, the next step is installation. Start by positioning each stringer so it’s level and evenly spaced, ensuring stability and balance.

• Attach to Deck Frame: Secure the top of each stringer to the deck frame using metal brackets or bolts, depending on the deck’s design. This connection is critical for stability, so be sure to follow recommended installation practices.
• Anchor to Ground: The bottom of the stringers should sit firmly on a concrete pad or similar stable surface to prevent shifting. Anchor them with brackets or bolts, ensuring that each stringer is secure and aligned.

Proper installation is essential for safety and longevity, so take extra care during this step.

Final Steps and Safety Checks

After installing the stringers, conduct a thorough safety check to ensure your stairs are secure and ready for use.

• Inspect Attachments: Check that all bolts and brackets are tightly fastened, with no loose components that could affect stability.
• Apply Wood Preservative: Treat all exposed edges, especially any cuts, with a wood preservative to prevent rot and extend the lifespan of the stringers.
• Prepare for Treads and Risers: Before installing the treads and risers, confirm that the stringers are level and evenly spaced to support the next construction phase.