ADU Rules in Washington DC, DC (2026)
ADU rules, permit requirements, size limits, and fees for Washington DC, DC. Source-cited from official municipal code.
Yes, ADUs are allowed in Washington DC, DC.
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: size varies by zoning — see official source (max height: 22 feet (detached verified 22 ft); attached unit ambiguous — zone-dependent height applies). Attached ADU: 35% of gross floor area of house.
| Type | Max Size | Max Height |
|---|---|---|
| Detached ADU | See official source | 22 feet (detached verified 22 ft); attached unit ambiguous — zone-dependent height applies · Verified June 4, 2026 · Source |
| Attached ADU | 35% of gross floor area of house · Verified June 4, 2026 · Source | See official source |
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: Varies.
| Fee Type | Amount |
|---|---|
| Plan Check | $300–$1,500 |
| Building Permit | $500–$3,000 based on construction value |
| Impact Fees | None |
| School Fees | None |
| Total Estimate | See official source |
Permit Timeline
Washington DC ADU Permit Timeline: No official statutory timeline in 11 DCMR § 301; DOB administrative guidance suggests 6-12 weeks for ADU projects but not verified from regulatory text. 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: no minimum. Rear setback: 7.5 ft from alley centerline.
Parking Requirements
Parking Requirements: No explicit ADU parking waiver found in fetched 11 DCMR § 253 cache. Parking exemption may exist in a separate parking subtitle not captured in the 2026-06-04 dcregs.dc.gov fetch.
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.
- Single-Family Lots
- 1
- Multifamily Properties
- Additional units per R-5 zone density provisions
Statewide Preemption
ADU Preemption
We could not confirm a statewide ADU preemption statute for District of Columbia.
View District of Columbia preemption detailsHistoric District Considerations
Historic District Requirements: Washington DC has 28 historic districts where additional design review may be required for ADU construction. Design review approval is required before obtaining a building permit for properties in historic overlay zones. Washington DC has one of the most extensive historic preservation systems in the US. The DC Historic Preservation Office (DCSHPO) oversees 28+ historic districts and approximately 15,000 historic properties in the DC Inventory of Historic Sites. Major districts include Georgetown (National Historic Landmark District), Capitol Hill Historic District, Dupont Circle Historic District, Logan Circle Historic District, Mount Pleasant Historic District, and many more. Certificate of Appropriateness (CoA) required from the DC Historic Preservation Review Board (HPRB) or the Mayor's Agent for exterior changes. This affects a very large proportion of DC residential properties, particularly in central neighborhoods. Source: https://historicpreservation.dc.gov/ Look up historic district boundaries at: https://historicpreservation.dc.gov/page/dc-inventory-historic-sites
Frequently Asked Questions
Can I build an ADU in Washington DC?
Yes. Washington DC, DC allows accessory dwelling units. On a single-family lot you can build 1.
How big can an ADU be in Washington DC?
The maximum size for a detached ADU in Washington DC is No explicit sqft cap found in 11 DCMR § 253.8 (accessory apartment in accessory building) in the fetched dcregs.dc.gov cache. Not applicable: attached uses GFA percentage; detached has no explicit sqft limit verified in fetched dcregs.dc.gov cache..
How long does it take to get an ADU permit in Washington DC?
The typical ADU permit timeline in Washington DC is No official statutory timeline in 11 DCMR § 301; DOB administrative guidance suggests 6-12 weeks for ADU projects but not verified from regulatory text.. Total estimated permit fees are No official fee total in fetched regulatory text; DC DOB fee schedules are administrative documents not in 11 DCMR zoning code..
Do I need extra parking for an ADU in Washington DC?
Washington DC parking rules for ADUs: No explicit ADU parking waiver found in fetched 11 DCMR § 253 cache. Parking exemption may exist in a separate parking subtitle not captured in the 2026-06-04 dcregs.dc.gov fetch.
Do I have to live on-site to have an ADU in Washington DC?
Owner-occupancy requirement in Washington DC: Either the principal dwelling or accessory apartment unit shall be owner-occupied for the duration of the accessory apartment use.
Source: 11 DCMR (DC Municipal Regulations, Title 11 — Zoning) — Accessory Dwelling Unit provisions; DC Home Rule Charter. Last verified April 6, 2026. View source