What Is an ADU? An ADU or Accessory Dwelling Unit, also known as second unit, granny flat, in-law unit, and so on, is a secondary housing unit on a residential lot. The ADU workbook packet Our ADU workbook provides more information about constructing an ADU. SUBSCRIBE Get the ADU Resources packet Name Email Loading... ADU REGULATIONS IN CITIES OF Blog ADU SAMPLES ADU is an all-in-one platform that covers every aspect of creating an accessory dwelling unit on your property. CONTACT NOW