Building height shall be the vertical distance to the highest point of the roof for flat roofs; to the deck line of mansard roofs; and to the midpoint between the eaves and the highest ridge for gable, hip, and gambrel roofs, measured from the curb level if the building is within ten feet of the front property line, or from the average elevation of the ground under the building.
If a building has more than one gable, hip, or gambrel roof, the highest gable, hip, or gambrel roof shall be used to determine the height of the building.
The average elevation of the ground shall be determined by adding the elevation of the lowest point of the lot covered by the building to the elevation of the highest point of the part of the lot covered by the building, and dividing by two. Height measurements shall be based on the existing topography of the site before grading. For an addition to an existing building the height measurement shall be based on the average elevation of the existing grade within five feet of the structure.