Section 193. Frame buildings

No  frame  building  shall  be  erected or
  maintained upon the same lot  with  a  dwelling  converted  after  April
  twenty-eighth, nineteen hundred thirty, nor shall any frame building not
  occupied  on  April  thirteenth,  nineteen  hundred forty, as a multiple
  dwelling be altered or converted to such use; except that if  the  walls
  of  a  frame converted dwelling are faced with a veneer of brick and the
  entrance story is occupied by not more than one  family,  such  entrance
  story may be altered so that it may be occupied by two families.