roof height
The distance from base level to the upper surface of the structure's highest hollow or enclosed portion.
The roof height of any building is the vertical elevation from its base to the highest exterior portion of the shell enclosing its interior space. This excludes spires, parapets, and other protruding non-habitable elements. In the event of ambiguity between the enclosing shell and the projecting element, then the roof's thickness shall be established by setting its height 10 cm above the highest reach of inhabitable space inside the building.
In the absence of any differentiating elements, the roof height is equal to the architectural or tip height (i.e. when the roof is the highest element of the building).
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.