Arlington County ADU rules — what you can build and when.
Detached ADUs allowed since 2019 — one of Virginia's most established programs.
Verify locally — rules are changing ahead of July 1, 2027. This page reflects our working understanding at publication. Always confirm with the Arlington County zoning department before you design or file. We handle that verification as part of every Readiness Assessment.
Arlington in one screen.
- Detached ADUs allowed by administrative permit since 2019
- Size ~750 sf detached / 35% of combined floor area
- Owner-occupancy required today (preempted by SB 531)
- Lot coverage, tree preservation and parking often the binding constraints
Reading between the lines.
Arlington County has one of the most mature ADU programs in Virginia. Since the 2019 zoning update, homeowners have been able to add a detached backyard unit by administrative permit — a functional by-right process — in addition to interior conversions.
The county's constraints tend to be dimensional rather than procedural: dense lots, tight setbacks, tree preservation, lot-coverage limits, and parking requirements. Careful site planning matters more here than in most Virginia jurisdictions.
Owner-occupancy is currently required, which SB 531 preempts on July 1, 2027. Beyond that, SB 531's most tangible effect in Arlington will be locking in the $500 local permit-fee cap.
Arlington answers.
Are detached ADUs allowed in Arlington County?
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Yes. Arlington has allowed detached accessory dwellings by administrative permit since 2019, making it one of Virginia's most established ADU jurisdictions.
How big can an Arlington ADU be?
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Detached units are generally capped at about 750 square feet, or 35 percent of the combined floor area of the primary dwelling and ADU — whichever is less.
Do I have to live on-site to have an Arlington ADU?
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Yes, owner-occupancy of the primary dwelling is currently required. SB 531 preempts that requirement on July 1, 2027.
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