Within the principal dwelling or in an accessory building
All ADU guides District of Columbia ADU code path
Can you build an ADU in District of Columbia?
Washington, DC allows one accessory apartment as a matter of right in most R zones, but the principal-house size, zone, unit location, lot occupancy, alley access, and building permits still matter.
District-wide zoning rightJurisdiction posture
One in qualifying R zonesProtected or locally permitted count
Jurisdiction guide liveLocal brief coverage is still expanding
The jurisdiction-wide starting point.
These fields stay separate because a broad jurisdiction policy, a limited geographic mandate, and a property-specific approval are not the same answer.
One in qualifying R zones
Must remain secondary to the principal dwelling and meet zone/building standards
Zone-specific parking rules apply
The official guide describes owner and occupancy conditions by configuration
Certificate-of-occupancy and rental requirements may apply
What the headline does not settle.
These are the common edges that can move a project outside the protected or simplest path.
R-19 and R-20 follow different rules.
Accessory-building siting and principal-dwelling floor area can change matter-of-right eligibility.
Historic review, building code, fire separation, lot occupancy, and covenants remain separate checks.
What decides the actual lot.
Jurisdiction law is one layer. These checks turn it into a parcel-specific feasibility answer.
- Zoning district, legal principal dwelling, and the municipality's current ADU ordinance
- Lot coverage, setbacks, height, access, parking, and any nonconforming structures
- Sewer or septic capacity, water service, utilities, and fire access
- Wetlands, flood hazard, coastal, wildfire, historic, HOA, deed, and condominium restrictions
A practical verification path.
Stop at the first unresolved layer rather than designing past a constraint.
Confirm the parcel, governing municipality, zoning district, and legal use of the primary home.
Choose an internal, attached, or detached concept and test it against the controlling size and dimensional rules.
Retrieve the current zoning text, permit checklist, utility records, and every overlay that applies to the site.
Resolve wastewater, building, fire, access, environmental, and private-title constraints before final design.
Submit the required plans, complete inspections, and obtain every approval and occupancy document before use.
Sources behind this guide.
Official sources support published legal claims. Comparison sources are labeled and used for orientation only.
Reviewed August 6, 2026.
Jurisdiction rules are the start, not the verdict.
The free guide is live. Property-specific paid briefs will open only after local source coverage is verified.
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