Washington

DC functions as both state and city for ADU regulation. The District's Zoning Regulations of 2016 (ZR16, Title 11 DCMR), adopted by the DC Zoning Commission in Case 08-06A and effective September 6, 2016, established 'Accessory Apartment' as a use category permitted as a MATTER OF RIGHT in most R (Residential House) zones — with the conspicuous exceptions of R-19 and R-20, where an accessory apartment requires Board of Zoning Adjustment special-exception approval. The matter-of-right pathway is the District's by-right ADU regime; it covers accessory apartments inside the principal dwelling and accessory apartments in detached accessory buildings. Key constraints: (i) owner-occupancy of either the principal dwelling OR the accessory apartment for the duration of the use; (ii) the accessory apartment may not exceed 35% of the gross floor area of the house; (iii) any new external entrance may not be on a wall facing a street; (iv) max occupancy 3 persons in the accessory apartment (combined 6 in R-19/R-20); (v) minimum gross floor area for the principal dwelling per a table in 11 DCMR § U-253.7(a). RF (Residential Flat) zones do NOT permit accessory dwelling units in a dwelling unit in the RF-1 zone, which is a meaningful exclusion across DC's row-house neighborhoods.

The District's by-right zoning pathway operates against PUBLIC zoning — it does not vacate private contractual restrictions in condominium declarations. In DC's row-house neighborhoods, where many properties are organized as condominiums (RF-1 zone exclusion of accessory units in dwelling units further compounds this), the practical ADU pathway requires both the zoning right AND the absence of a CC&R prohibition.

DC operates a dedicated CONSUMER ACCESSORY APARTMENT FINANCING PROGRAM — the Residential Accessory Apartments Program (RAAP), administered by the DC Department of Housing and Community Development (DHCD). RAAP supports the creation of residential accessory apartments at existing residential properties throughout the District. This is genuinely an ADU-specific public financing program (one of the few in the country at the state/equivalent level). Separately, DHCD administers the Home Purchase Assistance Program (HPAP), which provides interest-free loans of up to $202,000 in gap financing plus $4,000 in closing-cost assistance for qualified DC homebuyers — useful for ADU-builders acquiring with intent to add, but HPAP itself does not fund the ADU buildout. The DC Housing Finance Agency (DCHFA) co-administers HPAP and issues mortgage-revenue-bond first mortgages through its DC Open Doors program for first-time and qualified non-first-time buyers.

• Residential Accessory Apartments Program (RAAP)
• Home Purchase Assistance Program (HPAP)
• DC Open Doors (DCHFA first-mortgage program)
• Employer Assisted Housing Program (EAHP)

DC's most important ADU-relevant program is RAAP (covered in stateFinancing). On the regulatory side, ZR16's matter-of-right § U-253 accessory-apartment pathway functions as a District-wide streamlined-review mandate — accessory apartments in qualifying R zones move on the standard ministerial-permit track without conditional-use or special-exception review (except in R-19/R-20). DC has no statewide impact-fee waiver because DC has no impact-fee regime in the conventional sense; DC's permit-fee schedule is set by DOB and applies uniformly. The Office of Zoning maintains the Zoning Handbook as the authoritative interpretive resource, and the Coalition for Smarter Growth's ADU DC Homeowner's Manual is the de facto consumer pre-permit guide.

• Matter-of-right accessory-apartment pathway (ZR16 § U-253) — The District's by-right ADU pathway. Eliminates conditional-use/special-exception review in qualifying R zones (everything except R-19/R-20). ADU permits processed ministerially against the limited list of statutorily-allowed restrictions.
• Office of Zoning (DCOZ) Zoning Handbook — DC Office of Zoning's authoritative interpretive resource for ZR16, including the accessory-apartment pathway. Practitioners rely on the Handbook for current Zoning Administrator interpretations.