The ADU cannot exceed 33% of the heated square footage of the main dwelling or 800 square feet, whichever is smaller.

Additionally, the combined floor area of all detached buildings on the lot cannot exceed 33% of the heated square footage of the main dwelling. The square footage of a detached garage, shed, etc. will be included in this calculation.

Detached ADUs are allowed in the following zoning districts:

• Residential 80 (R-80)
• Residential 40 (R-40)
• Residential 20 (R-20)
• Mixed Use Overlay District with an approved plan
• Town Center Medium Density Residential (TC-MDR)
• Town Center Low Density Residential (TC-LDR)
• Town Center Low Density Residential (TC-LDR12)
• Cottage Business & Residential (CB&R)

ADUs within or attached to the primary dwelling (called “Utility Dwelling Units” or UDUs in Cary’s Land Development Ordinance) are allowed in all residential zoning districts except Residential Multi-Family (RMF).

Locate your site’s zoning by using the Property Research Map.

• Enter the address of the proposed ADU (upper left corner of the map)
• Click on the “i” (upper right corner of the map)
• Click on the parcel on the map
• Information about your property will populate on the right side of the map. Locate your zoning district.

ADUs must meet setback, buffer and easement requirements which vary from lot to lot. A survey or plot plan is required when applying for your building permit and an “as built survey” may be required after construction to confirm you are following your building setbacks.

There may be limitations of the lot that prohibit the construction of the ADU in a preferred location.

The ADU is included as part of the principal parcel and cannot be sold apart from the primary dwelling.  

The process for assigning an address to an ADU is initiated when the building permit application has been submitted for review.  An applicant may request a separate address.   

You may request a separate water and electric meter, but you will need to pay for the development of those costs. 

Cary does not regulate owner occupancy of the principal dwelling or the ADU. 

No. Manufactured homes, recreational vehicles, and travel trailers cannot be used as an ADUs.   

Fees are calculated after the review has been completed and approved.  There is a $50 processing fee for the Accessory Use Permit in addition to the building permit fee.   

Only residential uses are allowed in an ADU.   

Application Process

Permits are processed through Cary’s electronic plan review portal. 

Create user account in the electronic plan review portal.

• Click the “Register” button located in the upper right-hand corner of the home page

• Confirm your email address by clicking the link in your email after you create the account

Complete the application online and upload documents

• Select “Submit a Project for Review” (yellow button located mid-page)

• For Application Category select “Accessory Use Permits”

• Application Type “Accessory Use – Dwelling Unit”

• Project Title: Enter your address and the permit type ADU or UDU

Upload Documents Required documents

All required documents shall be uploaded as individual PDFs and named accordingly (i.e. site layout, property owner approval, etc.)

Required documents for an ADU permit application

• Property Information (Heated square footage of residence and proposed square footage for the ADU.)

• Property Owner Authorization (If applicant is not the property owner on the county record, include a signed authorization for the work by the property owner.)

• Floor plan of ADU (Highlight the area of the ADU and include the square footage for the ADU.)

• Property plot plan or survey (Sample Plot Plan)

• Contractor information and license numbers
• Accessory/Utility Dwelling Unit Application (Complete this form and upload it when you apply for your building permit.)

If you have additional questions, email 311@carync.gov include your address, the scope of work you are proposing, and the additional information needed.  Allow staff 3 to 5 business days to respond.