Everything homeowners ask about building an ADU in Arlington — answered with 2026 data.
Yes, ADUs are allowed in Single-family residential zones in Arlington, VA. The maximum size for a detached ADU is 35% of combined floor area up to 750 sq ft (45% up to 500 sq ft if the main dwelling is under 1,000 sq ft); new detached accessory buildings are also footprint-capped at 560 sq ft (R-5/R-6) or 650 sq ft (other R districts). Attached ADUs can be up to Same 750/500 sq ft rule as detached; basement ADUs have no size cap. Arlington has an ADU-friendliness score of 6/10. Check our full Arlington ADU rules page for complete zoning details.
ADU construction in Arlington typically costs $170,000-$340,000. The cost per square foot averages $170-$340. Garage conversions are more affordable at $90,000-$200,000, while prefab ADUs cost $130,000-$290,000. Permit fees add $2,800-$4,500 to your budget. See our detailed Arlington ADU cost guide.
Detached ADUs in Arlington can be up to 35% of combined floor area up to 750 sq ft (45% up to 500 sq ft if the main dwelling is under 1,000 sq ft); new detached accessory buildings are also footprint-capped at 560 sq ft (R-5/R-6) or 650 sq ft (other R districts). Attached ADUs are limited to Same 750/500 sq ft rule as detached; basement ADUs have no size cap. Junior ADUs (JADUs) have a cap of Not allowed. Maximum height is Lesser of 1.5 stories or 25 ft for a detached accessory dwelling (standard since the May 2019 ordinance). You are allowed up to 1 ADU per lot on a qualifying lot.
Rear setback: 5 ft (interior lots); 10 ft (corner lots). Side setback: 5 feet (to the wall). Front setback: A detached accessory dwelling must be at least 25 ft from any street and 8 ft from the main dwelling. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
No new space required if the lot already has any off-street parking; lots with none need 1 space only if a county study finds the block 65%+ parked. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Required - the owner must occupy the main dwelling or the accessory dwelling as their primary residence (recorded covenant; SB 531's changes arrive July 1, 2027). Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Arlington is typically 50-75 days. Plan check: 2-3 weeks. Pre-approved plans availability: Available.
Average ADU rental income in Arlington: 1-bedroom units rent for $1,700-$2,200/month, 2-bedroom units for $2,100-$3,000/month. Short-term rentals: Not permitted. Expected ROI: 5-7% annual return.
The minimum lot size for an ADU in Arlington is None specified - eligibility is by zoning district (R-20 through R2-7) with a one-family dwelling. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Arlington, a garage conversion typically costs $90,000-$200,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.