If more than one commercial establishment is located on the same floor of a building, the signs accessory to all such establishments, except for projecting signs that comply with the provisions of Section 101-131 (Permitted projection), shall be of equal height and mounted or painted on a common sign board. All signs or common sign boards shall be located as follows:

(a)        if accessory to uses on the ground floor of a building, the sign or common sign board shall be located within a band extending the full length of the street wall, which band shall have a lower limit of eight feet above the ground floor and an upper limit coincident with the bottom of the lowest window sill on the second floor, but in no event more than 16 feet above curb level;

(b)        if accessory to uses on the upper floor of a building, the sign or common sign board shall be located between the highest window lintel of the floor on which the use is located and the lowest window sill of the floor above, but in no case more than 25 feet above curb level;

(c)        no sign may be located so as to obscure any cornice, except that a non-illuminated sign may be attached to a cornice if such sign consists of individual letters, emblems or figures mounted on open metal mesh attached to the cornice and finished to match the cornice, provided that the cornice remains visible; and

(d)        no sign or common sign board shall extend above the parapet wall or roof of the building on which it is displayed.