Washington DC allows ADUs in most residential zones as matter-of-right (2016 change). Size limited to 35% of primary dwelling (attached) or 450 sq ft (detached). Owner-occupancy required. Historic district considerations.
Zoning & Size Requirements [1]
| Allowed Zones | Most R (residential) zones; varies by specific district |
| Max Size (Detached) | Greater of 30% of required rear yard OR 450 sq ft |
| Max Size (Attached) | 35% of gross floor area of primary dwelling; maximum 1,000 sq ft total |
| Max Size (JADU) | N/A (DC uses basement apartments/ADUs) |
| Max Height | 2 stories; 22 ft maximum (detached) |
| Max Units | 1 accessory apartment per lot only |
Setback Requirements [1]
| Rear Setback | Minimum 7.5 ft from alley centerline (if applicable) |
| Side Setback | Standard zone requirements |
| Front Setback | Standard zone requirements |
| Parking Required | Not required for ADU (only primary dwelling) |
| Owner Occupancy | Required - either main house or ADU must be owner-occupied |
| Min Lot Size | 1,200 sq ft gross land area minimum for detached |
Permit Process & Fees [2]
| Approval Process | DCRA (Department of Consumer and Regulatory Affairs) issues permits. Optional Preliminary Design Review Meeting (PDRM) recommended. |
| Review Timeline | 6-12 months total (planning through final inspection); 8-12 months typical |
| Permit Fees | $1,000-$3,000 building permits; additional utility costs |
| Impact Fees | Utility connection fees apply |
| Plan Check | 4-6 weeks; longer for complex projects |
| Pre-Approved Plans | Standard basement conversion and detached plans available |
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Construction Costs
| Average Build Cost | $150,000-$250,000 |
| Cost per Sq Ft | $300-$400 |
| Garage Conversion | $0-$0 |
| Prefab ADU (Installed) | $100,000-$150,000 |
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Rental Income Potential
| Avg Rent (1 Bedroom) | $1,400-$2,000 |
| Avg Rent (2 Bedroom) | $1,800-$2,800 |
| Short-Term Rental | Rental license required if renting; 30-day minimum suggested but not mandated |
| Est. Annual ROI | 10-15 year payback; strong appreciation in DC market |
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Recent Law Changes
What's Changed Recently
- 2016 zoning update made ADUs matter-of-right
- Owner-occupancy requirement remains (Subtitle U §253)
- Rental licensing required for renting ADU
- Historic district overlays add complexity to some properties
Tips for Building an ADU in Washington
- PDRM meeting strongly recommended to clarify requirements
- Basement conversions most common (cheaper than detached)
- Owner-occupancy is mandatory; cannot be absentee landlord
- Rental license required if renting; obtain from DCRA
- Plan for 6-12 month timeline
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Washington Planning Department — ADU Information Planning Department — Accessed 2026-03-15
- Washington Building Department — Permit Information building_dept — Accessed 2026-03-15
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