We’re lucky to have relationships with the expert instructors and craftspeople at Seattle Central College’s Wood Technology Center. In this video series, Catie Chaplan, a veteran instructor, guides us through some of the foundational carpentry concepts and methods for framing a basic equal-pitch hip roof, as taught in the center’s curriculum. 

Catie is dedicated to teaching the next generation of highly skilled carpenters. As a professional builder for 31 years, she's worked for general contractors, boat builders, and cabinet shops, and has owned and operated a residential design-build company in Seattle since 2002. She's been an instructor at the Wood Technology Center for the past 25 years, where she currently leads the carpentry program and teaches computer-aided design (CAD) and computer numeric control (CNC) classes.

Throughout the Framing a Hip Roof series, Catie shows us how to calculate theoretical hip roof framing (meaning that the calculations go to the very center of the roof), then how to adjust those calculations for the thickness of the materials used in different parts of the roof where pieces come together (this is called adjusting for "reality"). 

In this video, Catie shows us how to calculate the different measurements needed to lay out hip rafters using a construction calculator; then, how to use those calculations to lay out your cut lines on the actual rafter. 

To lay out a hip rafter, you’ll need to know the pitch, span, run, height-above-plate, head plumb adjustment, and overhang of your roof. 

  • Roof pitch tells you how many inches the roof rises for every 12 inches of run. In the video, Catie uses 7/12 as an example pitch value—7" being the rise, 12" being the run. 
  • Span is the overall width of the building.
  • Run is simple—it’s half the span (or half the overall width). 
  • Height-above-plate is the vertical or plumb distance from the birdsmouth seat or level cut to the top edge of the rafter.
  • Double-cheek cuts at the head of the hip rafter are how you'll adjust the head of the hip rafter to fit between the king common rafters.

How to use a construction calculator to lay out a hip rafter

To determine the overall length your hip rafter needs to be, you need to calculate the length from the center point of the roof ridge to the outside corner of the building, then the length of the overhang, then how much to shorten the rafter for reality. 

To calculate the length from the center point to the outside corner of the building using a construction calculator, enter the run of the building, then the pitch, then hit the hip/valley button. Be sure to include feet and inches when you type in the measurements.

To calculate the overhang, enter the run of the overhang into the calculator, then pitch, then hit the hip/valley button. 

To calculate the head plumb cut adjustment, enter half the width of the ridge, followed by the run, then the pitch, then hit the hip/valley button.

To find the length of the rafter, add the measurement from the center point to the outside corner of the building and overhang values and subtract the head plumb cut. 

These calculations give you the measurements needed to lay out your hip rafter. To watch the full tutorial, begin the video at 4:07.