International Building Code 312.1
312.1 General. Buildings and structures of an accessory character
and miscellaneous structures not classified in any specific
occupancy shall be constructed, equipped and maintained to
conform to the requirements of this code commensurate with
the fire and life hazard incidental to their occupancy. Group U
shall include, but not be limited to, the following:
Agricultural buildings
Aircraft hangars, accessory to a one- or two-family
residence (see Section 412.3)
Barns
Carports
Fences more than 6 feet (1829 mm) high
Grain silos, accessory to a residential occupancy
Greenhouses
Livestock shelters
Private garages
Retaining walls
Sheds
Stables
Tanks
Towers