What Is an Accessory Building?

Outdoor Buildings and Garden Structures

Outdoor pergola

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Accessory buildings are outdoor structures such as attached or detached garages, sheds, playhouses, storage buildings, pergolas, garden structures, greenhouses, private studios, boathouses, pool houses, cabanas, and other similar residential buildings. She-Sheds--often vintage trailers dolled up and accessorized as a backyard glamping escape, private getaway, or "big girl" playhouse--would also be considered an accessory building. This type of shed is used exclusively by the owners or occupants of the house or main building. Legally, most accessory buildings are not permitted to be used as sleeping quarters or as living space. Also, they can't be used to store commercial vehicles.

Guidelines

Most cities, counties, or local governments have ordinances about accessory buildings in which rules are stated in detail. Consult your city or county website for rules and laws, as they can vary.

Depending on the ordinance, accessory building guidelines might include the following:

  • They must be limited to two plumbing fixtures.
  • Some cities do not allow accessory buildings to have kitchen facilities (stove, oven, refrigerator, etc.).
  • Are usually open-air structures, such as gazebos and trellises
  • For zoning purposes, pools and spas are also considered accessory structures.
  • Can't be air-conditioned
  • Must be detached from the residence by a minimum distance of five to six feet, with eaves of the accessory building at a minimum distance of four feet. Again, this can vary according to city or county planning departments.
  • Accessory buildings are not allowed in required front yard setbacks or within side yards in the front 2/3 of the lot.
  • Usually limited to one story. In areas that allow two-story accessory buildings, structures can't exceed 30 feet in overall height.
  • Zoning laws dictate maximum heights; for typical one-story structures, 12 to 15 feet is a common limit, except if the structure has a sloped, pitched, gable, or hip roof.
  • In most municipalities, building permits can be required for all accessory buildings or structures greater than the certain square footage of the floor area (or the roof area for trellis-type structures); for instance, 120 feet is standard square footage.
  • Electrical/plumbing permits are required.
  • Barns are considered accessory buildings if they are used for the shelter of livestock raised on a residential property, the storage of agricultural products, or the storage and maintenance of farm equipment and agricultural supplies. Barns are usually not considered animal enclosures.
  • Attached garages and carports, storage buildings, workshops, hobby shops, and other similar structures that are for non-habitable purposes are considered accessory buildings. In most cases, the total area allowed on a lot is limited to 25 percent of the living area of the main residence.
  • If a garage, carport, storage building, workshop, hobby shop, or another non-habitable accessory building is attached to a pool house, art or music studio, or recreation room, the entire structure must meet the local setback requirements for the main building.
man working in garden office
 Peter Cade / Getty Images

History

In colonial times, many people worked at home: Their properties were large enough to accommodate their trades, whether they were doctors, lawyers, farmers, or blacksmith. Using your home for both living and working reasons was economically practical and acceptable if not commonplace. Industrialization of the 19th and early 20th centuries drove more workers out of their homes and into factories and larger cities to seek higher-paying and more steady work. 

Zoning eventually became a normal way to deal with the separation of work and home, to protect nearby home occupants and manage environmental concerns. Home workshops close to other homes (picture row houses), would have put the neighborhood at risk if potentially toxic materials were used.

Also known as Accessory structure, structure, outdoor structure, gazebo, trellis, arbor, pool, spa, playhouse