1. In all Residence Districts, the obstructions set forth in Section 23-311 and 23-312, as well as the following obstructions shall be permitted within any required rear yard or rear yard equivalent. These allowances are generally common to Residence, Commercial and Manufacturing Districts.
   1. Breezeways;
   2. Fire escapes;
   3. Greenhouses, non-commercial, accessory, limited to one story or 15 feet in height above adjoining grade, whichever is less, and limited to an area not exceeding 25 percent of a required rear yard;
   4. Recreational or drying yard equipment;
   5. Sheds, tool rooms or other similar accessory buildings or other structures for domestic or agricultural storage, with a height not exceeding 10 feet above the level of the rear yard or rear yard equivalent;
   6. Solar energy systems, accessory or as part of an energy infrastructure equipment:
      1. on the roof of a building permitted as an obstruction to such yard, up to four feet in height as measured perpendicular to the roof surface; however, limited to 18 inches in height as measured perpendicular to the roof surface when located above a detached accessory building or other structure, or on any roof with a slope greater than 20 degrees; or
      2. affixed to solar canopies and located over any otherwise unenclosed accessory off-street parking space, provided that the height shall not exceed 15 feet above the level of the adjoining grade;
   7. Water-conserving devices required in connection with air conditioning or refrigeration systems in buildings existing prior to May 20, 1966, if located not less than eight feet from any lot line.
2. In all Residence Districts, the obstructions set forth in Section 23-311 and 23-312, as well as the following obstructions shall be permitted within any required rear yard or rear yard equivalent. 
   1. Balconies, unenclosed, subject to the provisions of Section 23-62;
   2. Parking spaces, off-street, accessory, for automobiles or bicycles, provided that:
      1. if accessory to a single- or two-family residence, the height of a building containing such parking spaces shall not exceed 10 feet in height above the adjoining grade and such building shall be detached from such residence. Parking spaces shall also be permitted in buildings allowed as permitted obstructions pursuant to paragraph (b)(4) of this Section, provided that the portion allocated to parking spaces does not exceed 10 feet in height;
      2. if accessory to any other kind of building containing residences, the height of a building, or portion thereof, containing such parking spaces within the rear yard, shall not exceed 15 feet above base plane. In addition, decks, parapet walls, roof thickness, skylights, vegetated roofs, and weirs, as set forth in Section 23-41 (Permitted Obstructions), inclusive, limited to 18 inches in height, as measured perpendicular to the roof surface, shall be permitted upon the roof of such accessory building within the rear yard;
      3. enclosed accessory parking spaces for bicycles shall be accessory to a residence other than a single- or two-family residence, attached to a building, and the area dedicated to such spaces shall not exceed the area of bicycle parking spaces permitted to be excluded from floor area pursuant to Section 25-85 (Floor Area Exemption);
   3. any portion of a building used for residential uses other than dwelling units in buildings containing qualifying senior housing, provided that:
      1. such zoning lot is located in an R6 through R10 District other than an R6B, R7B or R8B District;
      2. such building portion is located within 100 feet of a wide street;
      3. the height of such building portion does not exceed one story, or 15 feet above the adjoining grade, whichever is less; and
      4. such space shall be accessible to all residents of the building.
          

         In addition, decks, parapet walls, roof thickness, skylights, vegetated roofs and weirs, as set forth in Section 23-41 (Permitted Obstructions), inclusive, limited to 18 inches in height, as measured perpendicular to the roof surface, shall be permitted upon the roof of such portion of a building within the rear yard.

   4. for single- or two- family residences, any portion of a building used for residential uses, provided that:
      1. for any ancillary dwelling unit associated with a detached, zero lot line or semi-detached building, the height, at any level, shall be limited to one story, not to exceed 15 feet. However, where an accessory parking space is provided below a portion of a building containing an ancillary dwelling unit, the height of such building, and an associated ancillary dwelling unit, shall not exceed two stories or 25 feet in height above adjoining grade, whichever is less, including the apex of a pitched roof;
      2. for detached and zero lot line buildings, the height of all other portions of buildings not containing an ancillary dwelling unit shall be limited to two stories or 25 feet in height above adjoining grade, whichever is less, including the apex of a pitched roof; 
      3. the size shall be limited to an area not exceeding one-third of the rear yard or rear yard equivalent; and 
      4. where such building is free-standing, it shall not be closer than five feet to a rear lot line or side lot line. 
          

         In addition, parapet walls, roof thickness, skylights, vegetated roofs and weirs, as set forth in Section 23-41 (Permitted Obstructions), inclusive, limited to 18 inches in height, as measured perpendicular to the roof surface, shall be permitted upon the roof of such portion of a building within the rear yard. 

However, no portion of a rear yard equivalent which is also a required front yard or required side yard may contain any obstructions not permitted in such front yard or side yard.