Housing > Small House Society > Resources > Glossary Summary. This page describes how Accessory Dwelling Units are defined according to typical housing codes. The backyard studio pictured here, from DecoratedShed.com, is an example of an Accessory Dwelling Unit. The text below is taken from the City Code of Iowa City, Title 17 (Building and Housing), Chapter… Continue reading Accessory Dwelling Unit ADU and Accessory Building Use Structures as Defined by Housing Code