How to Calculate a Gambrel Roof

Gambrel roofs have two sides that meet in the center to form a raised ridge. Each side is split into two horizontal sections with differing slopes. The upper portion has a smaller pitch to increase available space in the upper floors. The lower roof portions have a steeper pitch that prevents snow and rain accumulation. This split-roof design is commonly found on older barns and 17th and 18th century homes.

Calculator

Instructions

- 1
  Determine the length of the roof.
- 2
  Determine the vertical height and horizontal width of one side of the upper roof.
- 3
  Divide the height by the width of the upper roof.
- 4
  Use a calculator with tangent functions to apply the inverse tangent (TAN-1 on most calculators) to find the angle of pitch in degrees of the upper roof.
- 5
  Square the height and width. Add them together.
- 6
  Find the square root. This is the flat width of the upper roof.
- 7
  Multiply the width by the length of the roof to find the total area of the upper roof.
- 8
  Repeat Steps 1 to 7 to calculate the measurements for the lower roof.

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