Arlington, TX Accessory Structures: ADU Rules (2026)
ADU rules in Arlington, TX, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Maximum ADU size
- 800 square feet or less
- Density treatment
- Counts toward lot's max dwelling units
- Parking requirement
- 1 space per ADU
- Allowed placement
- Attached, detached, or with a garage
- Garage apartment density rule
- Counts as a unit in RM-12, RMF-22, NMU, RMU
Summary
Arlington caps accessory dwelling units at 800 square feet and counts each toward the lot's maximum dwelling-unit total, but only requires one parking space per ADU. Units can sit inside, attached to, or detached from the primary home, including above or beside a garage.
3. Additional Standards for Specific Neighborhood Building Types a. Accessory Dwelling Unit (ADU): (i) ADUs shall be any dwelling unit 800 sq.ft. or under in conjunction with a primary dwelling unit on the same lot. (ii) It shall be counted towards the maximum number of dwelling units permitted on the lot; however, for the purposes of calculating number of parking spaces required, only one (1) parking space shall be required per each ADU. (iii) Accessory dwelling units may be located within or attached to the main structure on the lot or in a detached structure on the lot or with a garage.
Full Breakdown
a, part of the Neighborhood Building Type standards adopted under the UDC rewrite (Ord. 26-019, effective June 1, 2025), defines an ADU as any dwelling unit of 800 square feet or less built in conjunction with a primary dwelling on the same lot. That unit counts toward the maximum number of dwelling units allowed on the lot under the applicable sub-district's density rules, but the parking calculation is lighter: the code requires only one parking space per ADU regardless of how many bedrooms it has.
Placement is flexible by design: an ADU may be located within the main house, physically attached to it, built as a fully detached structure elsewhere on the lot, or combined with a garage (a garage apartment). F, adds that in the RM-12, RMF-22, NMU, and RMU districts specifically, an accessory garage apartment is counted as a full dwelling unit for density calculations on the site, the same treatment as any other ADU. 7-3, they must also meet whatever setback and build-to standards apply to accessory buildings in that lot's base sub-district (TN, UN, CMU or Core), since the 800-square-foot cap governs size, not placement.
Violations & Fines
Development Services reviews ADU square footage and unit-count compliance at building permit application; an ADU built over 800 square feet, or one that pushes total units on the lot past the sub-district's density cap, can be denied a certificate of occupancy until the floor area is reduced or the unit is reclassified and brought into compliance with the applicable density limit.
Frequently Asked Questions
How big can an accessory dwelling unit be in Arlington?
Does building an ADU reduce how many units I can put on my lot?
Can my ADU be a garage apartment?
Sources & Official References
Other rules in Arlington
How Arlington compares: Easiest Cities to Build an ADU·Texas rules heatmap·Compare Arlington to another location·View the Texas accessory structures overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.
ADU Rules in Nearby Cities
How other cities in Tarrant County handle adu rules.