What factor determines the number of rafters needed for a gable roof?

The number of rafters needed for a gable roof is primarily determined by the length of the roof and the spacing of the rafters. This is because rafters are installed in a linear arrangement along the span of the roof, and the overall length dictates how many rafters will fit into that space based on the chosen spacing. For example, if the rafters are spaced 24 inches apart along a 20-foot-long roof, the calculation would involve dividing the total length by the spacing interval to determine the total number needed.

While the height of the roof, the type of roofing material, and the angle of the pitch are important for various aspects of roof construction, they do not directly affect the number of rafters required. The pitch might impact the size and type of rafters needed, but it does not change the count based on the linear distance and the spacing criteria. Each of these other factors plays a role in design and aesthetics or material selection, rather than directly determining the quantity of rafters.