Arlington Accessory Dwelling Unit and Secondary Living Unit Requirements
In the City of Arlington, Secondary Living Units (commonly known as ADUs) are permitted in all residential zoning districts but are strictly reserved for use by family members or relatives and may not be rented or leased. These units are limited to a maximum of one bedroom and one kitchen, and if detached, the structure's floor area cannot exceed 50 percent of the primary residence’s floor area [Section 12.3.5.N]. Additionally, the City of Arlington Unified Development Code requires that any attached unit must have a separate independent entrance not connected to the primary structure [Section 12.3.5.N].
Authorized Districts
The City of Arlington allows different types of accessory residential units depending on the specific zoning of the property. The most common form is the "Secondary Living Unit," which is permitted subject to supplemental standards in most residential areas.
| District Type | District Names | Secondary Living Unit | Garage Apartment |
|---|---|---|---|
| Residential | RE, RS-20, RS-15, RS-7.2, RS-5, RM-12, RMF-22, VG | Permitted* | Permitted* (RM/RMF only) |
| Mixed-Use | DB, NMU, RMU | Not Listed | Permitted |
| Non-Residential | LO, OC, NC, CC, GC, HC, BP, FH, LI, IM | Not Permitted | Not Permitted |
*Permitted subject to Supplemental Use Standards in Article 3. [Section 3.3.4].
Secondary Living Unit (SLU) Requirements
The City of Arlington Unified Development Code defines a Secondary Living Unit as a second single-family residential unit located on the same lot as the primary unit. It must provide independent provisions for living, sleeping, cooking, and sanitation [Section 12.3.5.N].
Occupancy and Use Restrictions
- Family Only: The unit is strictly for use by family members or relatives of the occupants of the primary unit [Section 12.3.5.N].
- No Rentals: The unit shall not be rented or leased to any party [Section 12.3.5.N].
- Prohibited Structures: Mobile homes and HUD-Code manufactured homes are not considered accessory secondary living units in the City of Arlington [Section 3.3.6.L].
- Short-Term Rentals: In the City of Arlington, units located within a Cottage Community are specifically prohibited from being used as short-term rentals [Section 5.11.20].
Development Standards
- Unit Size: The structure must not contain more than one bedroom, one kitchen, and one bathroom [Section 3.3.6.L.2].
- Construction Timing: Accessory structures cannot be constructed or established until the construction of the primary structure is complete [Section 3.3.5.C].
- Parking and Area: The Secondary Living Unit must meet all standards applied to the primary structure, with the exception of minimum gross living area and off-street parking requirements, from which it is exempt [Section 3.3.6.L.1].
- Building Count: Only one secondary living unit is allowed per lot. This unit counts toward the total number of allowed accessory buildings on a property [Section 3.3.6.L.3].
General Standards for Accessory Structures
All accessory buildings in the City of Arlington, including detached ADUs, must comply with the following bulk and density requirements.
| Standard | Requirement |
|---|---|
| Maximum Height | 24 feet (unless otherwise exempted) |
| Maximum Floor Area | 50% of the floor area of the principal structure |
| Maximum Building Count (< 1 acre) | 3 total accessory buildings |
| Maximum Building Count (≥ 1 acre) | 5 total accessory buildings |
| Required Setback (Side/Rear) | Minimum 5 feet from property lines |
[Section 3.3.5 and Section 3.3.6.A].
Design and Aesthetics
The City of Arlington requires all accessory structures to be designed to be aesthetically compatible with the principal structure. Compatibility is measured based on:
- Building materials and colors;
- Building orientation and massing;
- Roof form and pitch;
- Window style and placement [Section 3.3.5.F and Section 3.3.6.A.2].
Setback Requirements
Secondary Living Units must adhere to specific placement rules on the lot to ensure safety and neighborhood character.
- Front Yard Placement: Enclosed accessory buildings (including SLUs) shall not be located between the front property line and an imaginary line drawn from the front corners of the main building to the side property lines [Section 3.3.6.A.3].
- Side Street Setbacks: On corner or reverse corner lots, a minimum setback of 15 feet is required from the side property line adjacent to the street. This may be reduced to 10 feet if a side screening fence is installed [Section 3.3.6.A.3.b].
- Arterial/Collector Adjacency: A minimum setback of 20 feet is required from the rear property line if it is adjacent to an arterial or collector street [Section 3.3.6.A.3.b].
Sections Cited
- Section 3.3.4: Use Tables for Accessory Uses and Structures
- Section 3.3.5: General Standards for All Accessory Uses and Structures
- Section 3.3.6: Supplemental Accessory Use Standards
- Section 5.11.20: Additional Standards (Cottage Communities)
- Section 12.3.5: Accessory Uses and Structures (Definitions)