Can This Go Here?

Chapel Hill ADU rules: accessory apartments and second units

Chapel Hill recognizes second units through its two-family dwelling provisions — commonly called accessory apartments or ADUs. They are possible in most residential districts, but size caps, appearance rules and the lot's own constraints decide whether a specific property can host one.

Checking a specific Chapel Hill property?

Get the zoning, setbacks, impervious budget and environmental constraints for any address — one property, the full picture, $25.

Check an address

The basic allowance

A two-family dwelling that includes an accessory apartment is a recognized use in Chapel Hill's residential districts. In practice that means a second, smaller dwelling unit associated with a single-family home.

Two limits do most of the work: the second unit may not exceed 50% of the floor area of the main dwelling or 750 square feet, whichever is smaller — and the building must still read as a single-family home from the street.

  • Size cap: the lesser of 750 sq ft or 50% of the main dwelling's floor area.
  • Appearance: the property must keep the character of a single-family home from the street.
  • Owner occupancy and permitting requirements are administered by the Town's planning department; confirm current conditions before design work.

The lot still has to cooperate

Even where an accessory apartment is allowed, the parcel decides. An attached or detached second unit must fit inside the district's street and interior setbacks, under its height limit, and within the lot's impervious surface budget — Chapel Hill caps low-density lots at 24% impervious surface unless a higher-intensity standard applies.

Detached backyard cottages face the strictest test: accessory structures carry their own placement rules, and stream buffers or the Resource Conservation District can remove the only open corner of a lot from consideration.

What to check before you spend on design

Our $25 property report answers the zoning, setback, impervious and environmental-constraint questions for your exact address — the due-diligence step before you pay an architect.

  • Your zoning district and its setbacks, height and impervious limits.
  • Whether a stream buffer, floodplain or conservation overlay crosses the buildable part of the lot.
  • Whether the existing house plus a second unit stays under the impervious cap.
  • Parking, utility and septic or sewer capacity for a second unit.

Sources

This guide is general information about Chapel Hill rules, not legal advice or a determination about any specific property. Rules change — confirm current requirements with the Town of Chapel Hill before building.

More Chapel Hill guides