A Gable Roof Extensions' width should always be the same as the main building's width.
A Drop Gable is a Roof Extension that is equal in width to the main building, but drops elevation from the main building.
A Double Gable is typically narrower than the main building and shares the main building pitch. It should be the same height, but it can be shorter than the main building, although it cannot be taller or wider than the main building.
A Gable Addition can be taller, shorter, wider, or narrower than the main building. It will typically have separate configurations in truss and pole spacing, ect.
Lengths and widths should be wholly divisible by 8, 10, or 12 feet. Other dimensions can be built, however; they typically add unnecessary project cost and complexity.
ISW = Inside wall - a portion of the main building girts and metal that separate the main building from one or more add on structures such as gable roof extension or lean-tos. By indicating yes we will leave the girts and metal in place (enclosed). By indicating no, we will remove the girts and metal (opened up). Leaving only the posts in place. Posts cannot be removed.