ADU Rules in Washington DC, DC (2026)

Washington DC, DC permits accessory dwelling units (ADUs) on residential properties. ADUs — also called granny flats, in-law units, backyard cottages, or secondary suites — are secondary housing units on a single-family or multifamily lot. State and local law governs the approval process. In Washington DC, the DC Department of Buildings (DOB) handles ADU permit applications. Below you will find the current size limits, setbacks, fees, and timeline for building an ADU in Washington DC.

ADU Size Limits

ADU Size Limits in Washington DC: Detached ADU: up to 1000 sq ft (max height: 20 feet). Attached ADU: Up to 35% of primary dwelling gross floor area. 11 DCMR 1000 series (Accessory Dwelling Units). Detached ADUs limited to 1,000 sqft or 35% of primary dwelling floor area, whichever is less. Internal/attached ADUs allowed up to 35% of primary unit floor area. DC does not use the California JADU concept. DC Zoning Commission has expanded ADU provisions through recent zoning amendments to address housing supply in the District.

Permit Fees

ADU Permit Fees in Washington DC: Plan check fee: $300–$1,500. Building permit fee: $500–$3,000 based on construction value. Impact fees: None. School fees: None or N/A. Total estimated permit cost: $1,000–$6,000 total fees. Washington DC does not impose development impact fees. DC Water (WASA) charges connection and capacity fees for new water/sewer connections. DC DHCD (Department of Housing and Community Development) offers affordable housing programs that may offset costs for income-restricted ADUs. No school development fees.

Permit Timeline

Washington DC ADU Permit Timeline: DC Department of Buildings (DOB) issues building permits. DC Access online portal for permit applications. Typical timeline: 4-8 weeks for building permit. Complex ADU projects may require DCOZ pre-application meeting. DC has a Fast Track building permit program for qualifying residential projects. Apply through the DC Department of Buildings (DOB) online permit portal. Phone: (202) 671-3500.

Setback Requirements

ADU Setback Requirements in Washington DC: Front setback: follows zone standard. Side setback: 3 feet. Rear setback: 12 feet. 11 DCMR 1000 series. Rear setback minimum 12 ft for detached ADUs. Side yard setback 3 ft. DC's row home neighborhoods (common in Capitol Hill, Columbia Heights, Shaw) have zero side setbacks for primary dwelling — ADUs sited in rear yards. DC has extensive alley network — many properties have alley access enabling rear-loading ADU placement.

Parking Requirements

Parking Requirements: No minimum parking required for ADUs in Washington DC. DC's outstanding transit network (Metro rail system, Circulator bus, Capital BikeShare) and walkability make parking requirements unnecessary. 11 DCMR explicitly waives parking for ADUs.

Restrictions & Requirements

• •ADU must be on same lot as primary residential dwelling
• •One ADU per lot in R-1-A through R-3 zones (detached or attached)
• •ADU cannot be separately subdivided and sold from primary lot except under specific condo conversion provisions
• •Historic preservation review required for properties in DC historic districts (extensive — approximately 30% of DC residential properties are in historic districts)
• •Rear yard open space minimums must be maintained per 11 DCMR by zone
• •ADU must have separate entrance from primary dwelling

How Many ADUs Are Allowed?

Number of ADUs Allowed in Washington DC: Single-family lots: 1. Multifamily properties: Additional units per R-5 zone density provisions. DC allows one ADU per single-family lot in R-1 through R-4 zones. DC has been expanding ADU provisions to address the District's severe housing affordability crisis. DC's high land costs make ADUs economically attractive for both owners and tenants. Second ADU may be allowed in R-5 zones.

Historic District Considerations

Frequently Asked Questions