Understanding Accessory Dwelling Units (ADUs)An Accessory Dwelling Unit (ADU) is a secondary dwelling unit that can be added to an existing property or can be attached to the main house. These units are also known as granny flats, in-law units, or secondary suites. ADUs serve as an excellent way of adding additional living space while utilizing the existing space and providing affordable housing options for residents of Philadelphia. ADUs are gaining momentum in Philadelphia as the city is working towards increasing the availability of affordable homes for its residents.
Permitted Zones for ADUs in PhiladelphiaIn Philadelphia, ADUs are legal and can be found only on properties occupied by a single-family occupancy in a semi-detached or detached structure within the permitted zones described by SS 14-604(11)(d) (Permitted Zones). These zones include: