1. Stairwells: We typically include the area of the stair in the lowest level area, then include it again for the number of floors less one. For example, a two story building building it is only included in the first story area. For a three story building we would include the area on the first and second stories, but not the third?
2. Elevator Shafts: We typically include it on the lowest story only, and consider the remainder a vent shaft as described in 502.1.
Are these the commonly used methods to calculate total building area? Are there any references/commentaries that clarify this?