Why is it incorrect to just find one side of a roof and double it when calculating the main body?

Finding one side of a roof and doubling it to calculate the main body would generally yield inaccurate results mainly because roofs can have rafters of varying lengths. Roof designs often feature asymmetry due to factors such as different slopes, additional features like dormers, or varying roofing materials which can lead to significant differences in the lengths of rafters. This variation means that simply doubling one side does not account for these differences, potentially resulting in an understating or overestimating of the total surface area.

Calculating the total area of the roof requires precise measurements of each individual side, taking into consideration angles and other structural features to arrive at an accurate total. By acknowledging the variation in rafter lengths, one can ensure that the measurements reflect the actual area that will need to be covered or worked on, leading to more reliable estimations in projects involving roofing.