Sign measurement shall be based upon the entire area of the sign, with a single continuous perimeter enclosing the extreme limits of the sign surface. For a sign painted or applied on a building, the area shall be considered to include the smallest rectangle or other shape which encompasses all lettering, numbering, designs, logos or lights, together with any background of a different color than the finish material of the building. The area of supporting framework, such as brackets or posts, shall not be included in the area if such framework is incidental to the display. When a sign has two or more faces or is composed of multiple signs each with a face, the sum of the areas of all the faces shall be included in determining the area, except where two faces are placed back-to-back and are at no point more than two feet from each other. In this latter case, the sign area shall be taken as the area of either face; and if the faces are unequal, the larger shall determine the area.