What To Know About Cutting Stair Stringers

Stair stringers makes your staircase safe and sturdy. Cutting them requires precision, careful planning, and the right tools to ensure your stairs meet building codes and provide reliable support. We’ll walk you through the entire process, from basic concepts to advanced techniques.

What Are Stair Stringers?

Stair stringers are the diagonal supports that run along the sides of a staircase, providing the framework for treads and risers. Typically cut from 2-by-12 lumber, stringers are notched to create a zigzag pattern that accommodates the steps. They transfer the load of the stairs and people using them to the upper and lower levels of the structure.

Importance of Proper Stringer Cutting

Accurately cut stringers are crucial for several reasons:

• Safety: Properly cut stringers ensure even step heights and depths, reducing the risk of trips and falls.
• Structural integrity: Well-cut stringers distribute weight evenly and provide adequate support for the entire staircase.
• Code compliance: Stringers must meet local building codes for riser height, tread depth, and overall staircase angle.
• Longevity: Correctly cut stringers are less likely to warp, crack, or fail over time.

Tools Needed for Cutting Stair Stringers

Here’s a breakdown of the essential equipment you’ll need for cutting stair stringers.

Measuring Tools

Accurate measurements are the foundation of well-cut stringers. Key measuring tools include the following:

• Tape measure: For determining overall rise and run, as well as individual step dimensions.
• Framing square: Helps lay out the stringer cuts with precision.
• Level: To ensure your measurements and cuts are plumb and level.

Cutting Tools

Once you’ve marked your stringers, you’ll need the following cutting tools:

• Circular saw: The primary tool needed for making the long cuts on your stringers.
• Handsaw, jigsaw, or reciprocating saw: For finishing cuts in corners where the circular saw can’t reach.
• Drill: Useful for creating pilot holes and attaching hardware.

Safety Equipment

Safety should always be a priority when working with power tools. Don’t forget these essential safety items:

• Safety glasses: Protect your eyes from sawdust and debris.
• Hearing protection: Reduces noise exposure from power tools.
• Work gloves: Guard your hands against splinters and sharp edges.

Calculating Stair Measurements for Cutting

Careful measurement is essential for cutting stair stringers. Here’s what to do.

Determining Overall Rise and Run

The first step in calculating your stair measurements is to determine the overall rise and run:

1. First, measure the total vertical distance from the finished lower floor to the finished upper floor. This is your overall rise.
2. Then, measure the horizontal distance the stairs will cover. This is your overall run.

Calculating Riser Height and Tread Depth

Once you have the overall rise and run, you can calculate the individual riser height and tread depth by using the following steps: 

1. Divide the overall rise by the desired number of steps to get the riser height. Most building codes allow a maximum riser height of 7 3/4 inches.
2. For tread depth, most codes require a minimum of 10 inches. This is a good standard to use, as deeper treads can weaken the stringer.

For example, if your overall rise is 25 inches:

25 ÷ 7.75 = 3.23, which is rounded up to 4 risers

To find the individual riser height, divide the overall rise of 25 by the number of risers: 

25 ÷ 4 = 6.25 inches per riser

In the video below, general contractor Tom Silva demonstrates how plan out a stair build.

Selecting the Right Material for Stair Stringers

Choosing the appropriate material for your stair stringers helps ensure the longevity and safety of your staircase. The right choice depends on various factors, including the location of the stairs and the expected load.

Types of Wood for Stair Stringers

These are the most common materials for stair stringers:

• Pressure-treated lumber: Ideal for outdoor stairs due to its resistance to rot and insects.
• Douglas fir: A strong, stable wood often used for interior stairs.
• Southern yellow pine: Another durable option suitable for both indoor and outdoor use.

Considerations for Stringer Material Selection

When selecting your stringer material, consider these factors:

• Moisture exposure: For exterior stairs, choose pressure-treated lumber or naturally rot-resistant wood.
• Load-bearing capacity: Heavier traffic requires stronger wood species.
• Appearance: For visible stringers in finished spaces, consider the wood’s aesthetic qualities.

Always use 2-by-12 lumber for stringers, regardless of the wood type, as smaller dimensions don’t provide adequate strength after notching.

In the video below, Tom Silva shares tips for installing an interior staircase.

Step-by-Step Guide To Cutting Stair Stringers

Now that you’ve gathered your tools and materials, it’s time to cut your stair stringers.

Marking the First Stringer

Marking the first stringer accurately sets the stage for the remaining stringers. Here’s how to get it right:

1. Lay a straight 2-by-12 on sawhorses.
2. Position your framing square with the rise dimension on the tongue and the run dimension on the blade, intersecting the edge of the 2-by12.
3. Clamp a scrap of wood to the underside of the square as a guide.
4. Mark the first cut with a pencil. The longer line is the tread cut (run), and the shorter line is the riser.
5. Move the square up the stringer, aligning the next tread cut with the top of the riser below, and mark the next tread and riser.
6. Continue until you’ve marked all tread and riser cuts.

Adjusting for Tread Thickness

To account for tread thickness, follow these adjustments:

1. At the bottom of the stringer, shorten the bottom riser cut by the thickness of your tread material. Lay out this bottom cut by holding the square on the riser line and drawing a line parallel to the bottom tread.
2. At the top, the deck framing or fascia will act as the top riser, so make the final cut square down from the top tread. The final cut on the stringer is usually laid out and made square down from the top tread, depending on how you plan to tie the stringers into the deck framing.

Remember, there will always be one less tread than there are risers because the deck itself acts as the top step.

Making the Cuts

The next step is executing the cuts with precision:

1. Use a circular saw to cut along your marked lines.
2. Stop the saw cuts at the inner corners to avoid overcutting.
3. Finish the cuts at the corners with a handsaw, jigsaw, or reciprocating saw.

After you cut the first stringer, use it as a pattern to lay out all the others.

Common Mistakes To Avoid When Cutting Stringers

Even experienced carpenters can make mistakes when cutting stair stringers. Here are some common pitfalls to avoid:

• Overcutting corners: This weakens the stringer. Always stop saw cuts at the inside corners and finish with a handsaw.
• Ignoring wood grain: Cut stringers so the grain runs parallel to the stair slope for maximum strength.
• Failing to adjust for tread thickness: This can result in an uneven first step.
• Using undersized lumber: Always use 2-by-12s for stringers to ensure adequate strength.
• Neglecting to check for square: Use a framing square consistently to ensure accurate cuts.

Advanced Techniques for Complex Staircases

While straight staircases are common, you may encounter situations that require more advanced stringer cutting techniques.

Dealing with Winders

Winders are triangular steps used to change the direction of stairs, often in tight spaces. To cut stringers for winders:

1. Calculate the rise and run for each winder step individually.
2. Mark and cut each winder step on separate stringer sections.
3. Join the stringer sections carefully, ensuring proper alignment and support.

Accommodating Landings

For stairs with landings, treat each flight of stairs as a separate unit with its own stringers. Ensure the landing is level and properly supported and attach the upper and lower stringers to the landing framing securely. 

Remember, complex staircases often require additional support beyond standard stringers. Consider consulting a structural engineer for large or intricate projects.

Attaching Stair Stringers to the Structure

There are several methods you can use when attaching stringers, such as the following: 

• Direct attachment: Fasten the stringer directly to the floor joists or landing framing using lag screws or bolts.
• Ledger board: Install a ledger board to the supporting structure, then attach the stringers to this board.
• Joist hangers: Use specially designed joist hangers to support the top of the stringer.

Using Stringer Connectors

Specialized hardware like the Simpson LSC Adjustable Stringer Connector can simplify attachment and provide additional support. These connectors allow for easy adjustment during installation and provide a strong, code-compliant connection.

Finishing Touches: Installing Treads and Risers

Once your stringers are cut and installed, it’s time to add the treads and risers. When adding treads and risers, use pressure-treated lumber or appropriate decking material for treads, especially for exterior stairs. Then, secure treads and risers with screws rather than nails for a more durable connection. Ensure treads are level and risers are plumb for a professional finish.

You may also want to consider adding a slight slope to exterior treads (about 1/8 inch per foot) to allow water runoff. If you encounter any squeaks after installation, you may need to fix squeaky stairs by reinforcing connections or adding shims.

Building Code Compliance for Stair Stringers

While building codes can vary by location, there are some common code standards for stairs to keep in mind for all homeowners:,

Standard Code Requirements

Most building codes specify these requirements:

• Maximum riser height (typically 7 3/4 inches)
• Minimum tread depth (usually 10 inches)
• Maximum variation in riser height or tread depth (often 3/8 inch)
• Minimum stairway width (typically 36 inches)
• Handrail requirements

Regional Variations To Consider

While many code requirements are standardized, some aspects can vary by region, such as the stringer spacing requirements, the specific materials allowed for exterior use, and any additional requirements for commercial or public staircases. Always check with your local building department for the most up-to-date code requirements in your area.

Troubleshooting Common Stringer Issues

Even with careful planning and execution, you may encounter issues with your stair stringers, such as the following:

• Creaking or squeaking: This often indicates loose connections. Reinforce with additional fasteners or add shims where needed.
• Sagging: If stringers sag over time, add additional support beneath them or consider replacing them with stronger material.
• Splitting: Small splits can be repaired with wood glue and clamps. Larger splits may require stringer replacement.
• Rot: For exterior stairs, replace any rotted sections and ensure proper water drainage to prevent future issues.

Maintaining and Repairing Stair Stringers

Proper maintenance can extend the life of your stair stringers and ensure continued safety. Regularly inspect your stairs and make repairs in a timely fashion to keep them in top condition. 

• Check for loose fasteners and tighten as needed.
•  Look for signs of water damage or rot, especially on exterior stairs.
• Inspect for cracks or splits in the wood.
• Ensure treads and risers remain securely attached to stringers.

When To Replace Stringers

While many issues can be repaired, sometimes replacement is necessary, such as when you notice the following: 

• Extensive rot or insect damage.
• Large cracks or splits that compromise structural integrity.
• Severe warping or twisting.
• When remodeling to meet updated building codes.

Our Conclusion

By following the steps outlined in this guide, you can create safe, sturdy, and code-compliant stairs for your home or project. Remember to always prioritize safety, use the right tools and materials, and double-check your measurements before making any cuts. While DIY stringer cutting is achievable for many homeowners, don’t hesitate to consult a professional if you’re unsure about any aspect of the process.