Low Density

Existing Home Conversions

Accessory Dwelling Unit (ADU)

Form: A secondary attached or detached living unit with private living amenities including bathroom and cooking facilities. Units can be accessed from within the main building, a separate entrance, or may be fully detached. From the outside ADUs will appear as either part of a single-family home, or a single-family home with an accessory building such as a garage or carriage house.

ADU Drawing

Before/After

In this rendering, an existing garage (left) is converted into an ADU that blends seamlessly with the existing home (right).

Local presence: ADUs are a traditional housing form found in Chester County, usually referred to as carriage homes. They are primarily found in urban centers, but are permitted in many suburban areas as well.

ADU Photo 1
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Zoning considerations: While municipalities can regulate ADUs in multiple ways, precautions should be taken to ensure regulations do not overly restrict ADU development. Extensive regulation may discourage the development of ADUs and decrease affordability. However, complete lack of regulation may allow ADUs to be built out of character with the neighborhood. ADU regulations can include considerations for permitted locations, resident restrictions, and form. Resident restrictions include requiring one of the units to be owner occupied, requiring units to be affordable, restricting purchase of ADUs, allowing ADUs to be used as short-term rentals, and restricting ADU residency to only relatives or caregivers. Form considerations include size, setback, permitting only attached or detached ADUs, and architectural design standards. These considerations can have impacts on the form ADUs take and whether they will enable missing middle housing.

See eTool: Accessory Dwelling Units

Zoning ordinance examples