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 local building department 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: Varies. Building permit fee: Varies. 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: Permit timeline has not been confirmed — contact the department for current processing times. Apply through the local building department 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: Parking requirements have not been confirmed — see official source.
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: not confirmed — see official source. Multifamily properties: not confirmed — see official source.
- 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 detailsFrequently 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