How Washington Handles Accessory Structures: A Practical Guide

Washington maintains 161 local ordinances across all categories, and 4 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Washington falls on the strict-to-permissive spectrum compared to other cities.

ADU Rental Restrictions

Before an owner can rent out an accessory apartment anywhere in the District, 11 DCMR-U § 253.13 requires a Residential Rental Business License from the Department of Consumer and Regulatory Affairs plus a housing-code inspection of the property, on top of the zoning conditions that already govern the unit itself.

Key details: License required: Residential Rental Business License, before renting. Issuing agency: Dept. of Consumer and Regulatory Affairs. Inspection required: Yes, for housing code compliance. Applies to: Any zone, in-house or detached-building units.

Renting an accessory apartment without first obtaining the Residential Rental Business License and passing the required housing-code inspection violates 11 DCMR-U § 253.13. As a zoning violation it is subject to the § 305.1 fine of up to $100 per day it continues, and the Department of Consumer and Regulatory Affairs' licensing enforcement can separately bar the rental from proceeding until the license and inspection are obtained.

ADU Owner Occupancy

An accessory apartment in the District only stays legal as long as an owner lives on the property. 11 DCMR-U § 253.5 requires either the principal dwelling or the accessory apartment to be owner-occupied for as long as the accessory unit is in use, and § 253.10(a) blocks the Board of Zoning Adjustment from waiving that requirement in any residential zone.

Key details: Core requirement: Owner must occupy dwelling or accessory unit. Waivable by BZA?: No, per § 253.10(a). Applies in: All R zones with accessory apartments. Related non-waivable rule: §253.10(b): R-1B/GT, R-3/GT occupancy cap.

Renting out both the principal dwelling and the accessory apartment with no owner living in either violates the owner-occupancy requirement of § 253.5, and because § 253.10(a) bars the Board of Zoning Adjustment from waiving that condition, there is no special-exception path around it. Under 11 DCMR § 305.1, the violation carries a fine of up to $100 per day it continues, and § 305.2 authorizes an injunction to stop the unlawful use.

Compared to other cities, Washington takes a harder line on adu owner occupancy. The enforcement and penalty structure reflects that.

Shed & Carport Rules

DC zoning caps a shed at 50 square feet and 10 feet in height under its own definition, and gives sheds a setback exemption other accessory buildings don't get: a shed can sit inside a required rear or side yard where larger accessory structures cannot.

Key details: Maximum shed area: 50 sq. ft.. Maximum shed height: Under 10 ft.. Shed rear/side yard placement: Allowed inside required yard. Other accessory building max size (R zone): Greater of 30% rear yard or 450 sq. ft.. Other accessory building max height (R zone): 2 stories / 22 ft..

A structure exceeding the 50-square-foot/10-foot shed threshold but placed in a required rear or side yard as though it were a shed is treated as a non-conforming accessory building, subject to a Department of Buildings stop-work order and required relocation or removal, or a variance/special exception application to the Board of Zoning Adjustment for relief from the setback.

ADU Rules

The District allows one accessory apartment per lot in residential zones under 11 DCMR-U § 253, capped at 35% of the house's gross floor area and three occupants (six if it's in the R-1B/GT or R-3/GT zone), with size and access conditions that differ for units inside the main house versus a separate accessory building.

Key details: Apartments allowed per lot: 1, matter of right in most R zones. Occupancy cap: 3 people (6 combined in R-1B/GT, R-3/GT). Floor-area cap: 35% of house's gross floor area. Min. house size, in-house unit: 2,000 sq ft (R-1), 1,200 sq ft (R-2). Detached-building units: Need permanent code-specific access, no roof deck.

Building or renting an accessory apartment that exceeds the 35% floor-area cap, the three or six-person occupancy limit, or the access standards of § 253.8 without an approved special exception is a zoning violation. Under 11 DCMR § 305.1, the owner faces a fine of up to $100 per day the violation continues, and § 305.2 lets the Attorney General or a specially harmed neighbor seek an injunction against the unlawful use.

The Bottom Line

Washington's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Washington is broadly strict or permissive.

All of the above reflects Washington's municipal code as of our last review. If you need specifics on fines, exemptions, or filing requirements, the detailed ordinance pages linked above have the full breakdown.