1111.11  REAR YARD.
   "Rear yard" means a space unoccupied except by a building of accessory use as herein permitted, extending for the full width of the lot between the extreme rear line of a building and the rear lot line, excluding steps, uncovered porches and covered but unenclosed porches on the first story which do not extend more than ten feet beyond the front wall of the building. (1955 Code. §1111.11)