5 county-level rules, plus city-specific rules for 1 city in District of Columbia, District of Columbia.
Verified from official government sources
DC allows accessory dwelling units (called 'Accessory Apartments') in most residential zones under 11 DCMR. Detached ADUs have a max footprint of 450 sq ft or 30% of rear yard. Attached ADUs are limited to 35% of the principal residence's gross floor area. Maximum 3 occupants per unit.
DC exempts a single storage shed up to 10 feet high and 6x8 feet from building permits. Sheds over 50 sq ft are classified as accessory buildings with additional requirements. Sheds may be placed in required rear and side yards under 11 DCMR.
Garage conversions in DC require DOB building permits and must comply with 11 DCMR zoning regulations. Converting a garage to habitable space triggers building code requirements including fire sprinklers for new construction, egress, electrical, and plumbing upgrades.
Carports in DC are treated as accessory structures under DCMR Title 11 Subtitle D and require a Department of Buildings building permit. Typical rear yard setbacks are 5 feet from side and rear property lines, with maximum accessory structure height of 20 feet and lot coverage caps based on zone. Historic districts require HPRB approval for any visible carport.
DC does not have a dedicated tiny home zoning category. Foundation-built tiny homes must meet the 2017 DC Construction Codes (IRC with DC amendments) and the Zoning Regulations' minimum dwelling standards. Tiny Homes on Wheels (THOWs) are classified as RVs under DC Code section 50-101 and cannot be used as permanent residences. ADU pathways offer a limited route.
1 cities in District of Columbia have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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