Week 7: How to Frame a Rough Opening

Oct 6, 2024

Lecture Notes: Calculating Heights for Window Rough Openings

Overview

  • Figuring out the heights of trimmers and rough openings for windows.
  • Windows are more complex than doors due to the inclusion of a rough sill.

Full Height Wall Calculation

  • Header typically placed right below the top plate and cap plate.
  • Example: For an 8-foot wall:
    • Wall height: 8 feet (96 inches)
    • 2 plates (top and bottom): 3 inches
    • 2x10 header: 9 inches
    • Subtracting these from the wall height gives a rough height for window placement.
  • Example Calculation:
    • With a 3-foot window, the window would start approximately 4 feet from the ground.

Important Considerations

  • Building Code Compliance: Ensure the header size is compliant with local codes depending on clear span, weight loads, and snow loads.
  • Header Calculation:
    • Measure from the top of the stud to determine where the header will sit.
    • Example for a 2x10: Measure down 9 and a quarter inches for the header placement.
    • Add 1.5 inches for filler right below the header.

Trimmer Height Calculation

  • Measure from the bottom of the stud to the bottom of the filler.
  • The trimmer fits underneath the filler.

Cripples Height Calculation

  • Calculate based on window rough opening dimensions.
  • Example window: 59 inches by 38 and a quarter inches.
  • To find the rough opening:
    • Add 3/8 inch all around the window dimensions.
    • Rough opening becomes 59 3/4 inches by 39 inches.
    • Measure down 39 inches from the bottom of the marked stud to find the rough sill location.

Steps to Follow

  1. Mark the Header Location: Measure and mark where the header and filler go.
  2. Determine Trimmer Height: Measure from the bottom of the stud to the bottom of the filler.
  3. Calculate Cripple Heights: Measure from the bottom of the stud to the bottom of the rough sill.
  4. Cut and Install: Cut all components to the measured lengths and proceed with installation.

Conclusion

  • This method helps determine where to nail components and ensures correct measurements for window installations. Always verify with local codes and adjust measurements as required for specific window dimensions.