International Residential Code

SUBJECT: Definition of Accessory Structure
CHANGE TYPE: Modification

ACCESSORY STRUCTURE. In one- and two-family dwellings not more than three stories high with separate means of egress, a building A structure not greater than 3,000 square feet (279 m2) in floor area, and not over two stories in height, the use of which is customarily accessory to and incidental to that of the main building dwelling(s) and which is located on the same lot.

CHANGE SIGNIFICANCE: By deleting the redundant language related to scoping and adding specific criteria, the 2006 International Residential Code (IRC) provides a comprehensive definition of accessory structures applicable to one- and two-family dwellings as well as townhouses that fall under the jurisdiction of the code. The new definition places a size limitation of 3,000 square feet and a story limitation of two stories, and emphasizes that these buildings are subordinate to the dwellings by addition of the word “accessory.” Buildings larger than the limitations provided in the definition will no longer be considered accessory to dwellings, and their use must be evaluated for deciding whether they fall under the IRC scoping authority or must be regulated by the International Building Code.