How do you calculate stringers?
Calculating Stair Stringers: A Step-by-Step Guide
Brief Summary
Calculating stair stringers involves determining the rise (vertical height), run (horizontal distance), and the number of steps needed to create a safe and comfortable staircase. Key measurements and calculations include the total rise, total run, individual riser height, tread depth, and the length of the stringer itself.
Expanded Answer
Measuring the Staircase
- Total Rise:
- Measure the vertical distance between the finished floor levels of the two floors connected by the staircase.
- This includes the thickness of the finished flooring on both levels.
- Total Run:
- This is the horizontal distance covered by the staircase.
- It’s measured from the face of the first riser to the face of the last riser.
- If there’s a landing, measure each stair run separately and add them together.
Determining Riser Height and Tread Depth
- Estimate the Number of Risers:
- Divide the total rise by a comfortable riser height (usually between 7 and 7 ¾ inches).
- Round the result up to the nearest whole number to get the number of risers.
- Calculate Exact Riser Height:
- Divide the total rise by the number of risers.
- Ensure all risers in a flight have the same height (variation should not exceed 3/8 inch) to avoid tripping hazards.
- Calculate Tread Depth:
- Use the “rise + run = 17-18 inches” rule of thumb for comfortable stairs.
- Subtract the riser height from 17 or 18 to determine the tread depth.
- The tread depth typically includes the nosing (the overhanging lip of the tread), which is usually about 1 inch.
Laying Out the Stringer
- Choose Stringer Material:
- Select a suitable material for your stringers, such as 2×12 lumber for most residential applications.
- Mark the Rise and Run:
- Use a framing square to mark the rise and run measurements on the stringer board. Start from the bottom and mark each step, ensuring accuracy.
- Cut the Notches:
- Carefully cut the notches using a circular saw or jigsaw, following the marked lines.
- Account for Tread Thickness:
- If your treads have significant thickness, adjust the first riser’s height to accommodate it. The height of the first riser should be the standard riser height minus the tread thickness.
- Verify and Install:
- Double-check your measurements and cuts before installing the stringers. Secure them to the supporting structure using appropriate fasteners and methods.
Conclusion
Calculating stair stringers requires careful measurements and adherence to building codes for a safe and functional staircase. By following these steps and considering the desired rise and run, you can confidently lay out and cut your stringers, providing a solid foundation for your staircase project.