What is half the span of a roof referred to as?

Half the span of a roof is referred to as the run. In roofing terminology, the span is the total horizontal distance from one side of the roof to the other. The run specifically indicates the distance from the midpoint of the roof to the edge, effectively making it half of the total span. This measurement is crucial for determining how steep the roof is and is often used in conjunction with the rise, which is the vertical distance from the top of the roof down to the ceiling or bottom of the roof structure. Understanding the run is important for roof construction and design, as it helps in calculating the pitch and slope, which are essential for water drainage and aesthetic considerations.

While terms like rise, pitch, and slope also pertain to roofing, they refer to different aspects: the rise is about vertical distance, pitch refers to the ratio of the rise to the run, and slope indicates the incline itself. These distinctions highlight why the run specifically is the correct terminology for half the span of a roof.