Can you build an ADU in Washington, DC?
Accessory apartments appear broadly possible in many R zones, but the provided evidence indicates owner-occupancy is required and R-19/R-20 need BZA special exception approval. For non-owner investors, the strategy is materially constrained.
Confidence: medium · Last researched May 2026
Accessory apartment / ADU in R zones rules
A secondary source states that one accessory apartment is allowed as matter-of-right in most R zones if the project meets Subtitle U §253 conditions.
- Owner-occupancy required: the owner must live in either the main house or the accessory apartment
- Maximum unit size of 35% of total home gross floor area
- Maximum occupancy of 3 persons in the accessory apartment
- Minimum house size thresholds vary by R zone
- Street-facing entrance restrictions vary by zone
Related questions
Are ADUs allowed in Washington, DC?
A secondary source states that one accessory apartment is allowed as matter-of-right in most R zones if the project meets Subtitle U §253 conditions.
Full investor analysis
You've seen the general rule. The full Washington, DC report shows which districts allow ADUs by-right vs. by special permit, the approval path and timeline, and the overlay/flood constraints that quietly kill ADU projects here. First town report is free.
Get the full Washington, DC report free →More about Washington, DC zoning
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This summary is AI-generated from public municipal sources and is not legal, engineering, or land-use advice. Always verify zoning with Washington, DC officials before making decisions.
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