Green ADU

Building an Accessory Dwelling Unit (ADU)

Learn more about ADUs a.k.a. Granny Flats or Backyard Cottages

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Detached ADU Detached ADU with Primary Duplex Attached ADU Converting an Internal Space Two ADUs on One Parcel (Frequent Transit Areas Only) Fast Track Program Benefits NC Building Code ADU FAQs

An Accessory Dwelling Unit (ADU) is a small, self-contained home that is located on the same lot as a primary dwelling.  ADUs may be detached, attached, or internal to the primary dwelling. An ADU may also be located above a garage or in a basement. They can be one story or two stories. To learn more about the process for permitting an ADU, choose your ADU type below. Fast Track ADUs must follow the new single-family dwelling process. 

Detached ADU

ADU rendering of a residence with an ADU

If you are building a new ADU that is detached from your principal dwelling, then you must follow the New Single-Family Dwelling process. Fast Track ADUs must also follow the new single-family dwelling process. 

If you are finishing an existing detached garage for ADU use, you must follow the ADU Change-of-Use process.

Detached ADU with Primary Duplex

ADU rendering of a duplex with an ADU

Only one detached ADU may be added to a parcel containing a duplex, which would result in three units on the lot.

Attached ADU

ADU Attached Graphic

If you are adding square footage to your home to create space for an ADU, you must follow the Accessory Structure and Addition process.

If your principal dwelling is part of a duplex, the attached ADU addition will be reviewed under the NC Commercial Code.

Converting an Internal Space

ADU rendering of finished and unfinished spaces

If you are converting an finished or unfinished space in your single-family home, you must follow the ADU Change-of-Use process.

If you are converting an internal space and are part of a duplex, only one of the two units may build an ADU. The ADU would be reviewed under NC Commercial Code.

Two ADUs on One Parcel (Frequent Transit Areas Only)

Two ADUs may be built only on parcels designated as being in a Frequent Transit Area. Please refer to UDO Section 2.6.3 for parcels in residential districts, and Section 3.6.2 for all others.

If two internal spaces in a single principal dwelling are converted into two ADUs, or if two ADUs are added to a duplex, they will be reviewed under NC Commercial Code.

Fast Track Program

The City of Raleigh is excited to launch the first ADU Fast Track program and online gallery in NC.  The Fast Track program makes constructing an ADU more accessible for Raleigh homeowners. Fast Track plans have be pre-reviewed for building code compliance before becoming part of an online gallery. Residents can view the gallery and purchase plans (from the designer) at a fee far below the typical design cost.

Visit the ADU Fast Track Online Gallery and learn more about the program.


ADUs can fill a small but important niche in equitable housing supply. They offer a range of benefits for Raleigh residents. ADUs can:

  • Increase the supply of relatively more affordable housing wherever they are built. The small size and absence of land costs often lead to the units renting at lower rates than apartments in the same neighborhood.
  • Offer a more desirable housing type for renters who don’t want to live in larger, multi-family communities.
  • Provide aging homeowners the opportunity to move into a smaller, more accessible home in their backyard while retaining their larger, main house for family or renters. This is often referred to as "aging in place."
  • Be ideal homes for people with disabilities or medical challenges for whom closer family attention and care are necessary.
  • Be a source of needed additional income for many types of households. Over time, most ADUs will deliver a significant return on investment. 

NC Building Code

Image of plans, ruler, level, drill and screws on a wooden table

Learn more about the 2018 NC Residential Building Code requirements for ADUs in Raleigh.


White ADU

The ADU FAQs page answers a lot of common questions about building an ADU in Raleigh. 



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