Stair stringers are the backbone of any staircase, providing the essential support for the treads and risers. Whether you’re building a new set of stairs or repairing an existing one, knowing how to cut the top and bottom of the stair stringer is a fundamental skill. In this guide, we are talking about how to cut the top and bottom of stair stringer, we will walk you through the process, starting with understanding the formula for stair stringers and moving on to practical steps for cutting them. We’ll also discuss calculating the rise and run of steps, and the standard rise and run ratio for stairs.
What is the Formula for Stair Stringers?
To start, you need to calculate the rise and run for your stairs. These measurements determine the angle and length of your stair stringers. Here’s the formula to calculate these values:
- Rise (R): The vertical height between two consecutive steps. It’s usually around 7 to 8 inches (17.78 to 20.32 cm).
- Run (T): The horizontal distance from the front edge of one step to the front edge of the next step, also known as the “tread.” A typical value is about 10 to 11 inches (25.4 to 27.94 cm).
- Stringer Length (SL): The hypotenuse of the right triangle formed by the rise and run. You can calculate it using the Pythagorean theorem: SL² = R² + T².
Knowing these measurements, you can proceed to cut the top and bottom of your stair stringers.
How to Cut the Top and Bottom of Stair Stringers
- Measure and Mark the Rise and Run: Begin by measuring the rise and run for your staircase. Mark these measurements on the stringer, ensuring that the top of the stringer will align with the top landing and the bottom with the lower landing or the ground.
- Cut the Stringer Top: Using a saw, cut the top of the stringer along the marked line, ensuring a clean and square cut. This will be the point where your stairs meet the upper landing.
- Cut the Stringer Bottom: Similarly, cut the bottom of the stringer along the marked line, creating the point where your stairs meet the lower landing or the ground.
- Cut the Notches: For each step, you’ll need to cut notches into the stringer to accommodate the treads and risers. These notches are typically rectangular and should be deep enough to securely hold the treads and risers in place. The depth of the notches should match the thickness of your treads and risers.
- Cut the Stringer Angles: If your stairs are going around a corner or need to meet a specific angle, you’ll need to cut the stringers accordingly. The angles at the top and bottom of the stringer should match the angle of the stairs.
- Test Fit and Adjust: It’s crucial to test fit the stringer to ensure it aligns correctly with the upper and lower landings and that the treads and risers fit snugly in the notches. Make any necessary adjustments to ensure a secure and precise fit.
How Do You Calculate Rise and Run of Steps?
To calculate the rise and run of individual steps within the stringer, use the following steps:
- Determine the Total Rise (TR): Measure the vertical height between the top landing and the lower landing or the ground.
- Determine the Total Run (TT): Measure the horizontal distance from the front edge of the upper landing to the front edge of the lower landing.
- Calculate the Number of Steps: Divide the Total Rise (TR) by your desired rise per step (R) to find the number of steps: Number of Steps = TR / R.
- Calculate the Actual Rise and Run for Each Step: Divide the Total Rise (TR) by the Number of Steps to find the Actual Rise (AR) per step: AR = TR / Number of Steps. Similarly, divide the Total Run (TT) by the Number of Steps to find the Actual Run (AR) per step: AR = TT / Number of Steps.
What is the Standard Rise and Run Ratio for Stairs?
The standard rise and run ratio for stairs is typically around 7-8 inches (17.78 to 20.32 cm) for the rise and 10-11 inches (25.4 to 27.94 cm) for the run. However, building codes and local regulations may dictate specific requirements for rise and run dimensions, so it’s essential to check and comply with these regulations in your area. Following these standards helps ensure the safety and comfort of those using the staircase.
Conclusion
Knowing how to cut the top and bottom of stair stringers is a fundamental skill when it comes to constructing or repairing stairs. By understanding the formula for stair stringers, you can calculate the rise and run dimensions and create precise, well-fitted stringers for your staircase. Whether you’re working on an indoor or outdoor staircase, precision and attention to detail are key to ensuring safety and structural integrity. Always adhere to building codes and local regulations to ensure your staircase meets safety standards.
