What is the Roof Pitch? What it Means

Our Steel Truss Pole Barn Kit has a steel gable truss system with a 3:12 pitch, but what exactly is pitch?

  • The roof pitch is a numerical measurement of the steepness of a roof.
  • The pitch of a roof is its vertical rise divided by its horizontal span (or “run”), what is called “slope” in geometry and stair construction, or the tangent function in trigonometry.
  •  typically expressed with the rise first and run second.
  • With our steel trusses being 3:12, for every foot the rise will be three inches, so a 20′ truss will rise 30″ in the center.
  • The lean too trusses in our pole barn kit carry

    This raised center barn has 2 pitches

    a 1:12 pitch therefore a 12′ lean to truss will rise twelve (12″) or ( 1″) for each foot

  • In the USA, the run is denominated by the number 12, giving a ratio of how many inches of rise or fall there are to each 12 inches (one foot) of run.
  • Countries which use metric measurement systems use a degree angle, or what fall there is per unit of run, and expressed as a “1 in x” slope, a 1 in 1 slope being 45°. Where convenient, the LCMs are used, e.g. a 3 in 4 slope, rather than “9 in 12” or “1 in 1 1/3”
  • US convention is to use whole numbers when even (e.g. “three in twelve”) or the nearest single or two-digit fraction when not (e.g. either “five and a quarter in twelve” or “five point two-five in twelve”, each expressed numerically as 5.25:12).
  • The exact roof slope in degrees is given by the arctangent. For example: arctangent (3/12)=14.0°
  • The primary purpose of pitching a roof is to redirect water and snow. Thus, pitch is typically greater in areas of high rain or snowfall.


  1.  “Pitch” Sturgis, Russell. A dictionary of architecture and building: biographical, historical, and descriptive. New York: The Macmillan Co. ;, 1901. 152. Print.
  2. ^ Jump up to:a b c d “Slope” def. 1. Schmid, Karl F.. Concise encyclopedia of construction terms and phrases. New York: Momentum, 2014. Print.
  3. Jump up^ Dictionary of Architecture & Construction, C.M.Harris.
  4. Jump up^ “Pitch” def. 24.c. Oxford English Dictionary Second Edition on CD-ROM (v. 4.0) © Oxford University Press 2009
  5. ^ Jump up to:a b “Pitch” def. 2. Knight, Edward Henry. Knight’s American mechanical dictionary: being a description of tools, instruments, machines, processes, and engineering; history of inventions; general technological vocabulary; and digest of mechanical appliances in science and the arts.. vol. 2. New York: J.B. Ford and Co., 1874. 1719. Print.