Wall signs (including painted murals used as signs). Wall signs, as defined in this chapter, shall be attached to the face of the building in a plane parallel to such face. Such sign shall not extend or project more than eight inches from the face of the building. Any such sign which overhangs any publicly owned property shall not extend higher than the top of the parapet, in the case of one-story buildings, and in the case of other buildings it shall not extend above the sill of the windows of the second story nor extend more than 15 feet above the outside grade. No wall sign or combination of signs on any single frontage in a business district shall exceed an area equivalent to 100% of the linear length of the structure on such frontage or a maximum of 50 square feet, whichever is less. Where an establishment for which signs are permitted has a rear entrance on a public way or parking lot or frontage on two or more streets, such as a corner, signs shall be permitted on each frontage, up to the maximum permitted for that frontage. Wall signs shall not cover, wholly or partially, any wall opening, including doors, fire escapes and windows, nor project beyond the ends of the wall to which they are attached. All such signs must be safely and adequately attached to said building wall by means satisfactory to the Building Official or his designee. Within an industrial district, one sign not exceeding 100 square feet is permitted for each street frontage from which access is provided to the lot.