How To Cut Stringers For Stairs On A Deck

Constructing stairs for a deck involves several crucial steps, with cutting the stringers being a pivotal component. Accurate stringer cuts ensure the stairs are safe, even, and aesthetically pleasing. This article details the process of cutting stair stringers for a deck.

Understanding Stair Terminology

Before commencing, familiarity with key terms is essential:

• Stringer: The structural member that supports the treads and risers.
• Tread: The horizontal part of the stair where you step.
• Riser: The vertical part of the stair between the treads.
• Rise: The total vertical height of the staircase, from the top of the deck to the ground.
• Run: The total horizontal length of the staircase.
• Unit Rise: The height of each individual riser.
• Unit Run: The depth of each individual tread.

Calculating Rise and Run

Accurate rise and run calculations are paramount for comfortable and code-compliant stairs.

Determining the Total Rise

Measure the vertical distance from the top surface of the deck to the ground (or landing surface). This measurement is the total rise.

Calculating the Unit Rise

Stair building codes often specify minimum and maximum values for the unit rise. A common range is 6-8 inches. Divide the total rise by a number that falls within that range to determine the approximate number of risers. If the result is not a whole number, adjust the number of risers until you achieve a unit rise within the acceptable range. Then, calculate the exact unit rise by dividing the total rise by the number of risers.

Example: If the total rise is 63 inches, dividing by 7 risers yields a unit rise of 9 inches (too high). Dividing by 9 risers yields a unit rise of 7 inches (acceptable). Therefore, you would have 9 risers, each 7 inches high.

Calculating the Unit Run

Building codes also typically specify a minimum tread depth. A common minimum is 10 inches. The unit run can be slightly larger than this, but avoid excessively deep treads. Select a value for the unit run based on code requirements and user comfort.

Calculating the Total Run

Multiply the unit run by the number of treads (which is always one less than the number of risers). This result is the total run.

Gathering Materials and Tools

Before cutting, assemble the necessary materials and tools:

• Stringer material (typically pressure-treated lumber)
• Circular saw
• Speed square
• Pencil
• Measuring tape
• Safety glasses
• Hearing protection
• Construction adhesive (optional)
• Framing square (optional, but recommended for accuracy)

Marking the Stringer

Accuracy is key during the marking process.

Setting Up the Speed Square

Place the speed square on the stringer material. Align the edge of the square with the edge of the lumber. Using the unit rise and unit run measurements, position the speed square so that the appropriate markings on the square align with the edge of the lumber. Securely hold the speed square in place during the marking process.

Marking the First Tread and Riser

Using a sharp pencil, trace the outline of the speed square, creating the shape of the first tread and riser on the stringer. Ensure the lines are clear and precise.

Marking Subsequent Treads and Risers

Carefully slide the speed square along the stringer, aligning the edge of the square with the previous riser mark. Repeat the tracing process to mark the subsequent treads and risers. Maintain consistent and accurate markings throughout.

Accounting for Deck Thickness

At the top of the stringer, where it attaches to the deck, you need to account for the thickness of the decking material. Subtract the decking thickness from the bottom of the last riser mark. This ensures the top tread will be flush with the deck surface.

Cutting the Bottom of the Stringer

At the bottom of the stringer, you need to subtract the thickness of the tread from the bottom of the first tread mark. This ensures the bottom step is the correct height. This cut is called the "birdsmouth cut".

Cutting the Stringer

Cutting should be performed with precision and safety.

Setting the Saw Blade Depth

Adjust the depth of the circular saw blade to slightly more than the thickness of the stringer material. Avoid setting the blade too deep, as this can be hazardous.

Cutting Along the Marked Lines

Carefully follow the marked lines with the circular saw, cutting out the tread and riser sections. Maintain a steady hand and a consistent cutting speed. Aim for clean, straight cuts. Avoid overcutting or undercutting the lines.

Cutting the Birdsmouth and Top Landing Sections

Pay close attention when cutting the birdsmouth and top landing sections, as these cuts are crucial for proper stair installation. Ensure these cuts are accurate and square.

Reinforcing the Stringer (Optional)

For added strength, consider reinforcing the stringer.

Adding Support Blocks

Attach support blocks to the inside corners of the tread and riser cutouts. Use construction adhesive and screws to secure the blocks in place. These blocks provide additional support and prevent the stringer from flexing or cracking.

Installing the Stringer

Proper installation is as important as accurate cutting.

Attaching to the Deck

Securely attach the top of the stringer to the deck frame. Use appropriate fasteners, such as lag screws or bolts, to ensure a strong and stable connection. Ensure the stringer is plumb and level.

Securing the Bottom of the Stringer

The bottom of the stringer should rest on a solid and level foundation, such as a concrete pad. Secure the stringer to the foundation using appropriate fasteners. Ensure the stringer is properly supported and does not move or shift.

Installing Treads and Risers

Attach the treads and risers to the stringer using screws. Ensure the treads are level and the risers are plumb. Maintain consistent spacing between the treads and risers.

Inspecting the Stairs

After installation, thoroughly inspect the stairs.

Checking for Stability

Test the stairs for stability by walking up and down them. Ensure the stairs do not wobble or creak excessively. Address any stability issues promptly.

Verifying Measurements

Double-check the rise and run of each step to ensure they are consistent and within code requirements. Correct any discrepancies.

Ensuring Code Compliance

Verify that the stairs comply with all applicable building codes. This includes requirements for handrails, guardrails, and stair width.

Why It Matters

Accurately cutting stringers is fundamental to building safe and durable deck stairs. Precise measurements and cuts contribute to a stable and code-compliant structure, ensuring the safety of users. Proper stringer construction also enhances the overall aesthetic appeal and longevity of the deck, increasing its value and enjoyment.