main roof height
The vertical elevation of the primary roofplate, not including small penthouses and turrets.
The main roof height is applicable to any buildings with a significant roof level below what is defined above as roof height. In general, this means the height of the first roof above the top floor to be included in the floor count, whereas the roof height will include the elevator box or mechanical room on top of the main roof. In ambiguous cases or buildings with sloped or curved tops, this data is generally not entered.
The measurement runs from the base of the structure, the level of the lowest significant open-air pedestrian entrance. A building on a slope therefore has one height rather than one per side, and a figure taken from the low side of the same building is a different number.
Two sources giving different heights for one building have usually measured from different levels rather than measured badly.