Everything homeowners ask about building an ADU in Durham — answered with 2026 data.
Yes, ADUs are allowed in All residential districts (RR, RS-20, RS-10, RS-8, RS-M, RU-5, RU-5(2), RU-M, RC) and any other district where household living is a permitted use: an ADU is an accessory use to Household Living (UDO Sec. 5.2.3) on a lot developed with one or two primary dwelling units (Sec. 5.4.2.B.1.a). Not permitted in Special Flood Hazard Areas or Future Conditions Flood Hazard Areas (Sec. 5.4.2.A). in Durham, NC. The maximum size for a detached ADU is 1,000 sq ft of heated floor area on a single storey, or 1,200 sq ft total across two storeys (UDO Sec. 5.4.2.B.4), and in every case less than the floor area of the primary house. RR District lots of 4 acres or more use a different cap: 50% of the house's heated floor area. On a single-family lot the detached accessory structure may be built as a two-unit duplex ADU as long as both units total no more than 1,200 sq ft (Sec. 5.4.2.B.1.d). Attached ADUs can be up to Same caps as detached: 1,000 sq ft on one storey, 1,200 sq ft total, and never equal to or larger than the primary structure. Durham has an ADU-friendliness score of 8/10. Check our full Durham ADU rules page for complete zoning details.
ADU construction in Durham typically costs $150,000-$400,000. The cost per square foot averages $250-$400+. Garage conversions are more affordable at $65,000-$140,000, while prefab ADUs cost $80,000-$137,000. Permit fees add Building & Safety schedule (effective 7/1/2018, still the posted schedule): new dwelling up to 1,200 sq ft $146 building permit + $146 plan review; electrical 100-200 amp service $156; mechanical heating/cooling system $125; plumbing for a new dwelling $170; Homeowner's Recovery Fund $10. Plus Planning review of the building permit $110 and Infrastructure Residential Building Permit Review $436.80 (Development Services fee menu, July 2026). About $1,300 in City fees for a new detached unit; a conversion or addition is priced as a residential addition/renovation ($125-$250 permit + $125 plan review, plus trade permits). to your budget. See our detailed Durham ADU cost guide.
Detached ADUs in Durham can be up to 1,000 sq ft of heated floor area on a single storey, or 1,200 sq ft total across two storeys. Attached ADUs are limited to Same caps as detached: 1,000 sq ft on one storey, 1,200 sq ft total, and never equal to or larger than the primary structure. Junior ADUs (JADUs) have a cap of No junior-ADU category in the Durham UDO. An internal conversion (basement, attic, attached garage) is simply an attached ADU under the same 1,000 / 1,200 sq ft caps. Maximum height is Detached: the accessory-structure limit, the greater of 2 storeys and 32 ft or the height of the primary house (Sec. 5.4.1.C); in Design Districts the lesser of 3 storeys or 40 ft and never taller than the house (Sec. 5.4.1.E). An attached addition follows the district limit for the house, 3 storeys / 40 ft in the RS and RU-5 districts (Secs. 6.3.1, 6.4.1). Interior conversions have no height test (Sec. 5.4.2.B.7.c). You are allowed up to One ADU per lot, on lots with one or two primary dwelling units on a qualifying lot.
Rear setback: 5 ft for a detached ADU in most residential districts; 3 ft in the RU and RC districts (UDO Sec. 5.4.1.B.1.a-b). An attached ADU (addition) must meet the house's rear yard, which is 25 ft in every RS, RU and RC district (Sec. 7.1.2). Side setback: 5 ft for a detached ADU; 3 ft in the RU and RC districts (Sec. 5.4.1.B.1.a-b). An addition follows the district side yard for the house: 12 ft in RS-20, 10 ft in RS-10, 9 ft in RS-8, 5 ft in RS-M, RU-5, RU-M and RC (Sec. 7.1.2). Front setback: A detached ADU must sit behind the front building line of the house (Sec. 5.4.1.B.1); beside the house is fine as long as it does not project past the front facade. On corner lots one of the two street yards may use the side-yard standard (Sec. 5.4.1.B.5); on flag lots the unit may be in front of the house (Sec. 5.4.1.B.6); RR lots of 2 acres or more may place it in front of the house outside the street yard (Sec. 5.4.1.B.1.c). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None: 'No parking is required for an accessory dwelling' (UDO Sec. 5.4.2.B.6; the ADU parking requirement was removed by a 2017 text amendment). The house keeps its own 2-space minimum under Sec. 10.3.1, which a driveway satisfies (Sec. 10.2.3). Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required. The 2006 UDO's owner-occupancy condition was removed by text amendment after a 2012 City Attorney opinion that it conflicted with state law (NC Court of Appeals, City of Wilmington v. Hill); Sec. 5.4.2 contains no occupancy, deed-restriction or rental condition. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Durham is typically No turnaround time is published. The plan-review fee is paid at submittal and status is tracked in Dplans / LDO; the first re-review is free, the second costs $200; an application with no activity for six months is voided and the plan-review fee is forfeited. Plan check: Digital plan review through Dplans: drawings split by trade as flattened PDFs under 200 MB, plan-review fee credited against the permit fee at issuance, sealed plot plan required for any new or changed footprint. An optional Enhanced Plan Review (face-to-face, $600 per hour) is available after one standard review round. Pre-approved plans availability: None. The City's Affordable ADU Pilot Program (Housing & Neighborhood Services with Coram Houses) offered 2% fixed 30-year construction loans of up to $80,000 to 20 homeowners who rent the unit to tenants at or below 80% of Area Median Income for 30 years; all 20 slots are filled and applications are closed.
Average ADU rental income in Durham: 1-bedroom units rent for $1,200-$1,550 (Zillow Sept 2026 average $1,195; RentCafe Aug 2026 $1,414; HUD FY2027 Fair Market Rent $1,554 for Durham-Chapel Hill)/month, 2-bedroom units for $1,550-$1,750 (Zillow $1,560; RentCafe $1,632; HUD FY2027 FMR $1,745). Durham rents were flat to slightly down year over year in 2026/month. Short-term rentals: The UDO (amended through June 2026) has no short-term-rental use category and Sec. 5.4.2 puts no rental or occupancy condition on ADUs, so zoning does not bar nightly rental; verify current City Code and any HOA covenants before listing. Expected ROI: Gross yield roughly 5-9% before expenses: $1,400-$1,550/mo ($17,000-$18,600 a year) on a $200,000-$300,000 build; net return is lower after property tax, insurance, vacancy and maintenance.
The minimum lot size for an ADU in Durham is No minimum lot size in Sec. 5.4.2 and density limits do not apply to ADUs (Sec. 5.4.2.B.1.c). The only lot-size trigger is the RR District, where 4 acres or more switches the size cap to 50% of the house. A legal nonconforming lot at least 30 ft wide may still be developed with a house under Sec. 14.3.2. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Durham, a garage conversion typically costs $65,000-$140,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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