For a complying or non-complying non-residential building existing on December 15, 1961, the Board of Standards and Appeals may permit an enlargement, provided that such enlargement shall not create any new non-compliance or increase the amount or degree of any existing non-compliance except as provided in this Section.

In all districts, the floor area ratio permitted under this Section shall not exceed the floor area ratio permitted under the applicable bulk regulations set forth in Article II, III or IV of this Resolution by more than 10 percent, or 10,000 square feet, whichever is less.