In plain words
In Washington, DC, many homeowners can add one accessory apartment without a public hearing. That holds only if the home and lot meet the rules. An accessory apartment is a small second home on the same lot as a house. It can be a basement unit, an addition, or a unit over a garage or in a carriage house.
DC has no towns or counties, so one set of zoning rules covers the whole city. Zoning is the set of rules about what you can build where. Since 2016, those rules allow an accessory apartment "as a matter of right" in most Residential House (R) zones. That means you need only a normal building permit, not a hearing, if you meet every standard.
Here are the main standards. The owner must live in the house or the apartment the whole time. No more than three people can live in the apartment. For a unit inside the house, the house must be a minimum size. The apartment can use no more than 35 percent of it. A unit in a backyard building needs permanent access to a street, such as a wide enough alley. If you miss a standard, you can ask for a "special exception." That means a hearing before the Board of Zoning Adjustment.
Rowhouse (RF) zones work differently. They allow two or more full homes on a lot by right. One can be in a backyard building with alley access.
In Georgetown's R zones, every accessory apartment needs a special exception.
Before renting, you need a rental business license and an inspection. Build only if the rules and your property allow it.
The rules at a glance
| State ADU law | Yes |
|---|---|
| Where the state rule applies | The whole District, which has no separate towns or counties. Accessory apartments are a matter-of-right use in Residential House (R) zones except R-1B/GT and R-3/GT in Georgetown (special exception there); rowhouse (RF) zones use a separate rule allowing two or more principal homes per lot. |
| Approved without a hearing? | Yes. Qualifying ADUs are approved by staff review, without a discretionary hearing. |
| Kinds of ADU the state protects | internal, attached, detached |
| ADUs per lot | 1 accessory apartment per R-zone lot; in RF zones 2 to 4 principal dwelling units depending on the zone (RF-1: 2). |
| Owner living on site | State law requires the owner to live on the property. |
| Parking | No added space for the accessory apartment: the parking table counts 1 space per principal dwelling for single-unit homes, and an accessory apartment is not a principal dwelling (our reading of 11 DCMR Subtitle C § 701.5). |
| Size | Inside the house: the house must have at least 2,000 sq ft of floor area in R-1 or 1,200 sq ft in R-2 and R-3 (garage excluded), and the apartment may use no more than 35% of it. In a backyard building: max 2 stories and 22 feet, footprint up to the larger of 30% of the required rear yard or 650 sq ft (R-1, R-2) or 550 sq ft (R-3). Max 3 occupants in the apartment. |
| Lot size and setbacks | No minimum lot size for the apartment itself. A detached apartment needs permanent access: an open passage at least 8 feet wide to a street, a 24-foot alley to a street, or a spot within 300 feet of a street by a 15-foot alley; otherwise a special exception. Backyard buildings sit at least 3 feet from the rear line (none if it abuts an alley or street) and 7.5 feet from an alley centerline, together take no more than 30% of the required rear yard, and in side yards keep the full side setback and 10 feet from the house; in R-1 and R-2 zones they also sit at least 3 feet from a side lot line (none if it abuts an alley or street). A new entrance on the house cannot face the street, except below the main level in R-3 zones (with a historic-district compatibility finding where applicable). No roof deck on a building with an apartment. |
| Fees | No ADU-specific fee rule; normal building permit fees and a Residential Rental Business License apply. |
| Short-term rentals | State law doesn’t set this. Before renting, the owner must get a Residential Rental Business License and a housing code inspection (11 DCMR Subtitle U § 253.13). DC's separate short-term rental licensing law was not reviewed here. |
What to do next
- Look up your lot's zone (R, RF or a Georgetown /GT zone) on the DC Office of Zoning map.
- Check the 11 DCMR Subtitle U § 253 standards: owner occupancy, the minimum house size and 35% cap for inside units, entrance placement, and street access for backyard units.
- If your home is in a historic district, plan for a compatibility review of any new street-facing door or exterior change.
- Apply for a building permit with DC's Department of Buildings; if you cannot meet a standard, plan for a BZA special exception (up to two standards can be relaxed, never owner occupancy).
- Before renting the unit, get a Residential Rental Business License and pass the housing code inspection.
- Read any condo or HOA covenants on your property before you design.
Grants, loans and tax breaks
- Residential Accessory Apartment Program (RAAP) pilot, DC DHCD (closed): A DHCD pilot run by The Roz Company that paid toward creating accessory apartments. About $1.65 million in FY22-FY23 funds produced five units. Homeowners earning above 120% of median family income had to rent to households below 60% of median income. It no longer accepts applications. Program page
What your town still decides
DC acts as both state and city. Its Zoning Commission writes the zoning regulations (Title 11 of the DC Municipal Regulations), and the Board of Zoning Adjustment (BZA) hears special exceptions and variances. A homeowner who meets every § 253 standard needs only a building permit. The BZA may modify or waive up to two standards, but never the owner-occupancy rule; asking to change three or more is treated as a variance, which is harder to win. The rental license rule in § 253.13 still names the Department of Consumer and Regulatory Affairs, whose licensing duties moved to the Department of Licensing and Consumer Protection in 2022. The accessory-building limits in Subtitle D were amended in 2021, 2025 and 2026, so check the current text before drawing plans.
Examples of local rules
- Georgetown R zones (R-1B/GT and R-3/GT): Every accessory apartment needs a BZA special exception. It is allowed only on the second story of a detached backyard building, balconies and projecting windows cannot face a neighboring single-family house, and the main house plus the apartment together are capped at 6 occupants. Source
- Residential Flat (RF) zones (rowhouse areas): No accessory apartment category. Instead 2 to 4 full homes are allowed per lot by right depending on the zone, including one in a backyard building with an 8-foot recorded passage to a street or a 15-foot alley route, no roof deck, and a 5-year wait for setback-area buildings built after January 1, 2013. Source
What we’re still confirming
- In RF zones, a rule bars turning certain backyard buildings built after 2013 into a home for five years; a recent zoning case proposed dropping it, so confirm with the Office of Zoning.
- Zoning commissioners asked the Office of Planning in late 2025 to study the owner-occupancy rule; we haven't found a formal proposal to change it.
Laws, bills and citations
The laws behind this (3)
- Accessory building rules for Residential House (R) zones (11 DCMR Subtitle D, Chapter 50 (§§ 5000-5005), Zoning Regulations of 2016; latest amendments ZC Order 24-20 (72 DCR 9494, Sept 5, 2025) and ZC Order 25-12 (73 DCR 9999, July 10, 2026), signed July 10, 2026, in effect July 10, 2026). Sets the size and placement limits for backyard buildings, which govern any detached accessory apartment. A lot may have only one accessory apartment; accessory buildings can be up to 2 stories and 22 feet tall, with a footprint up to the larger of 30% of the required rear yard or 650 sq ft (R-1, R-2) or 550 sq ft (R-3), and must keep small setbacks from lot lines and alleys. The Office of Planning's omnibus amendment (ZC Case 25-12, published July 10, 2026) raised the footprint caps from 450 sq ft; the 3-foot rear and side setbacks carry source notes for Orders 24-20 (2025) and 25-12 (2026). Read it
- Accessory apartments in Residential House (R) zones (11 DCMR Subtitle U § 253 (Accessory Apartment, R zones); Final Rulemaking & Order No. 08-06A (63 DCR 2447, March 4, 2016), amended by Order No. 18-16/19-27-19-27B (70 DCR 11297, Aug 25, 2023), signed March 4, 2016, in effect September 6, 2016). Allows one accessory apartment per lot as a matter of right (staff-reviewed building permit, no hearing) in R zones, either inside the house or in a backyard building with permanent street access. The owner must live in one of the two units, and no more than 3 people may live in the apartment. Units that miss a standard, and all units in Georgetown's R zones, need a special exception from the Board of Zoning Adjustment. Read it
- Second (and more) homes in Residential Flat (RF) zones (11 DCMR Subtitle U § 301.1 (Matter-of-right uses, RF zones); Final Rulemaking & Order No. 08-06A (63 DCR 2447, March 4, 2016), signed March 4, 2016, in effect September 6, 2016). In rowhouse (RF) zones, accessory apartments are not used; instead each lot may hold 2 (RF-1), 3 (RF-4) or 4 (RF-5) full principal homes by right, including one in a backyard building with an open passage or alley access. A backyard building built by right after January 1, 2013 inside a required setback cannot become a home for 5 years after its permit without a special exception. Read it
Sources
- 11 DCMR Subtitle D, Chapter 50 (§§ 5000-5005), Zoning Regulations of 2016; latest amendments ZC Order 24-20 (72 DCR 9494, Sept 5, 2025) and ZC Order 25-12 (73 DCR 9999, July 10, 2026) · official source
- 11 DCMR Subtitle U § 253 (Accessory Apartment, R zones); Final Rulemaking & Order No. 08-06A (63 DCR 2447, March 4, 2016), amended by Order No. 18-16/19-27-19-27B (70 DCR 11297, Aug 25, 2023) · official source
- 11 DCMR Subtitle U § 301.1 (Matter-of-right uses, RF zones); Final Rulemaking & Order No. 08-06A (63 DCR 2447, March 4, 2016) · official source
- DC Zoning Regulations, 11 DCMR Subtitle C Chapter 7 (vehicle parking), Table C § 701.5 · official source · checked 2026-10-03
- DC DHCD, Residential Accessory Apartment Program (RAAP) · official source · checked 2026-10-03
- DC Office of Planning, ZC Case 25-12 Omnibus Text Amendment setdown report (accessory building changes) · official source · checked 2026-10-03
- DC Office of Zoning, View Zoning Regulations (ZR16 effective September 6, 2016) · official source · checked 2026-10-03
- Citizen Portal, Zoning Commission debates larger accessory-building footprints and ADU rules (Nov 26, 2025) · checked 2026-10-03
This is general information, not legal advice. Your town, village, city or county decides what can be built on your property. If something here looks out of date, email the team.