Build Your ADU in Arlington County, VA
Design, permits and construction of accessory dwelling units, built to Arlington County’s rules by a contractor that builds nothing else.
- ADU max size
- 35% of the combined floor area of the house and the unit, up to 750 sq ft · 45% up to 500 sq ft where the house is under 1,000 sq ft
- Minimum lot size
- 5,000 sq ft
- Owner occupancy
- Required
- Off-street parking
- One off-street space where the property already has parking · waived if a county parking study shows the block below 65% capacity
- Allowed by
- Case-by-case review
- Rules current as of
- 2026-01-01
Can you build an ADU in Arlington County, Virginia?
Arlington County ADU Guidelines
The rules that decide whether, and what, you can build. The table below carries the specifics.
Up to 750 Sq Ft
ADUs cannot exceed 750 sq ft or 35% of the combined floor area of the main home and ADU — whichever is smaller. If the main home is under 1,000 sq ft, the cap is 45% up to 500 sq ft. Attached interior ADUs follow the same size formula.
All Residential R Zones
ADUs are permitted by-right in all Arlington residential zones: R-20, R-10, R-8, R-6, R-5, R-10T, R-15-30T, and R2-7. Only one ADU is allowed per property, and it cannot coexist with an existing family or caregiver suite on the same lot.
5 ft Side & Rear
Detached ADUs on interior lots must maintain at least 5 feet from side and rear property lines. On corner lots, the rear yard setback increases to 10 feet. The ADU must also be at least 8 feet from the main dwelling and no closer than 25 feet to any street.
560 or 650 Sq Ft
The maximum detached ADU footprint depends on your zoning district: 560 sq ft in R-5 and R-6 zones; 650 sq ft in R-20, R-10, R-8, R-10T, R-15-30T, and R2-7 zones. Height is capped at 1.5 stories or 25 feet, whichever is less.
Required by County
The property owner must live in either the primary home or the ADU as their principal residence. Rentals are permitted for terms of 30 days or more — short-term rentals (e.g., Airbnb) are not allowed on a property with an ADU. The ADU cannot be sold separately from the main home.
Administrative Approval
ADUs in Arlington require a full building permit plus any applicable trades permits (electrical, plumbing, mechanical). Design review ensures the unit is compatible with neighborhood character. Makara ADU manages the entire application process on your behalf.
| Requirement | Arlington County Standard |
|---|---|
| Maximum ADU size | 35% of combined floor area, up to 750 sq ft (45% up to 500 sq ft if main dwelling is under 1,000 sq ft) |
| Detached footprint — R-5 / R-6 zones | 560 sq ft maximum |
| Detached footprint — other R districts | 650 sq ft maximum |
| Units allowed per lot | One ADU per residential property |
| Eligible zones | All residential R zones (R-20, R-10, R-8, R-6, R-5, R-10T, R-15-30T, R2-7) |
| Side & rear setback (interior lots) | 5 ft minimum (10 ft rear on corner lots) |
| Separation from main dwelling | 8 ft minimum |
| Maximum height | 1.5 stories / 25 ft, whichever is less |
| Owner occupancy | Required — owner must occupy main home or ADU (under SB 531, from July 1, 2027, verified only at the time of application) |
| Rental rules | Leases of 30+ days permitted; short-term rentals (e.g. Airbnb) not allowed; ADU cannot be sold separately |
| Approval type | Full building permit plus trades permits (electrical, plumbing, mechanical) |
| Typical build time | Move-in ready in as little as 120 days from permit approval |
| Item | Arlington Standard (Zoning Ordinance §12.9.2) |
|---|---|
| What it is | An Accessory Dwelling (AD) Permit issued by the Arlington Zoning Division, required in addition to a Residential Building Permit |
| Sequence | The AD Permit comes first — the building permit can't be issued until the AD Permit is issued and the covenant is recorded |
| Eligible lots | One-family detached homes in the R-20, R-10, R-8, R-6, R-5, R-10T, R-15-30T, or R-2-7 districts; one AD per lot, with no existing AD or family/caregiver suite |
| Owner occupancy | The owner must occupy the main home or the AD as a primary residence; a Declaration of Covenants is recorded before the building permit issues |
| Occupancy limit | No more than three persons |
| What you submit | Floor plans of the main dwelling and AD, a scaled site plan, a certified plat, the covenant, and an acknowledgement of AD conditions |
| Pre-submission meeting | Recommended with the Zoning Division (zoningadmin@arlingtonva.us) before drawing plans |
| AD Permit review time | About 30 days after the application is accepted as complete by the Zoning Division |
| After construction | An Affidavit of Compliance is filed and a Certificate of Occupancy issued; the Zoning Administrator may inspect annually for ongoing compliance |
Regulations summarized from the Arlington County accessory dwelling program and the Arlington County Zoning Ordinance (ACZO). Last verified August 2026. Zoning rules change — confirm current requirements with Arlington County before finalizing your project.
Source: Arlington County Zoning Ordinance §12.9.2 and the county's Accessory Dwelling Permit program. Makara ADU manages the full process; confirm current requirements and fees with the Arlington Zoning Division before finalizing.
The Arlington County ADU Permit Process
- 01
Zoning & Eligibility
Confirm your R district, lot eligibility, size caps, and setbacks. Arlington recommends a pre-submission meeting with the Zoning Division — Makara ADU handles it, free.
- 02
Design & Drawings
Floor plans of the main dwelling and the accessory dwelling, a scaled site plan, and a certified plat — prepared to §12.9.2 and building-code standards.
- 03
AD Permit (Zoning)
File the Accessory Dwelling Permit with the Zoning Division. About 30 days after it's accepted complete, the Zoning Administrator issues it — and the Declaration of Covenants is recorded with the Circuit Court.
- 04
Building Permit (ISD)
Apply for the Residential Building and trades permits with Inspection Services. The building permit can't be issued until the AD Permit is issued and the covenant is recorded.
- 05
Build & Certificate
Construction, county inspections, the Affidavit of Compliance, and the Certificate of Occupancy — keys in hand, ready to occupy or rent.
Arlington County’s ADU Specialists
We don't build everything. We build ADUs. Based in Gaithersburg, we work with local permitting offices every week and know how each jurisdiction's rules shape what can be built.
Deep Arlington Knowledge
We know Arlington's zone-by-zone footprint limits, the 5-foot setback rules, and the county's design compatibility expectations inside and out. Our familiarity with the permitting office means fewer revision cycles and faster approvals.
One Contractor, Start to Finish
Architecture, permits, foundation, framing, MEP, finishes — Makara ADU manages the entire project under one contract. No coordinating between separate architects, engineers, and builders on a project this complex.
Fixed-Price Proposals
We quote your project in full before a shovel goes in the ground. No surprise change orders mid-construction. Arlington ADU projects have tight lot constraints — we plan for every variable upfront.
Built for Aging in Place
Many of our Arlington clients build ADUs to bring aging parents closer or to plan for their own future. We design single-floor, accessible units that work beautifully today and adapt gracefully over time.
ADU Types We Build in Arlington County
Most jurisdictions allow more than one ADU configuration. We help you choose the right one for your lot, your zone and your goals.
Detached Backyard Cottage
A fully independent structure in your backyard with its own entrance, kitchen and bath. The most flexible option, and the one most people picture. Size and placement follow the rules in the table above.
Attached & Basement ADU
A self-contained unit inside or attached to the house: a finished basement, a new wing, or a second-storey addition with its own entrance. Shares structure with the main home, which usually lowers cost.
Garage & Accessory Conversions
Turning an existing garage or outbuilding into a dwelling. Often the fastest and least expensive route, and frequently the easiest to approve.
What a Arlington County ADU Costs
Turnkey pricing depends on size, site conditions and finishes. The ranges below are typical all-in costs for a detached Makara ADU: design, permits and construction through certificate of occupancy. Basement and garage conversions cost less than new detached construction.
| Size | Typical layout | Turnkey price range |
|---|---|---|
| ~400 sq ft | 1 bed / 1 bath | $250,000–$295,000 |
| ~600 sq ft | 1 bed / 1 bath | $300,000–$350,000 |
Arlington County ADU FAQ
Can I build an ADU in Arlington County, Virginia?
Yes. Arlington County permits one accessory dwelling per residential lot in all R zoning districts, either attached to or detached from the main home. The property owner must occupy either the main dwelling or the ADU as their primary residence.
How big can an ADU be in Arlington County?
An Arlington ADU is limited to 35% of the combined floor area of the main home and the ADU, up to a maximum of 750 sq ft (or 45% up to 500 sq ft when the main dwelling is under 1,000 sq ft). New detached units are also footprint-capped at 560 sq ft in R-5 and R-6 zones and 650 sq ft in other R districts.
Are detached ADUs and backyard cottages allowed in Arlington?
Yes. Detached ADUs are allowed in Arlington's residential zones. A detached unit must sit at least 8 feet from the main dwelling, meet a 5-foot side and rear setback on interior lots, and stay within 1.5 stories or 25 feet in height.
Do I have to live on the property to have an ADU in Arlington?
Yes. Arlington currently requires owner-occupancy — the owner must live in either the main home or the ADU as their principal residence, recorded as a covenant. Under Virginia SB 531, effective July 1, 2027, a locality may require owner-occupancy only at the time of application, not on an ongoing basis.
Can I rent out my Arlington ADU or use it for Airbnb?
You can rent an Arlington ADU on leases of 30 days or longer. Short-term rentals such as Airbnb are not permitted on a property that has an ADU, and the ADU cannot be sold separately from the main house.
How much does it cost to build an ADU in Arlington, VA?
A turnkey detached ADU in Arlington typically runs from about $250,000 to $300,000 depending on size, site conditions, and finishes. Basement and garage conversions cost less. Makara ADU provides a fixed-price proposal before construction begins.
How long does it take to build an ADU in Arlington?
A Makara ADU can be move-in ready in as little as 120 days from permit approval . The full timeline — eligibility review, design and engineering, and county permitting — depends on Arlington review times and project scope.
Will Virginia's new ADU law (SB 531) change the rules in Arlington?
Virginia SB 531 requires localities to allow ADUs by-right in single-family zones beginning July 1, 2027, and caps ADU permit fees at $500. Arlington already allows accessory dwellings today through its AD Permit process, so homeowners can build now; SB 531 adds a statewide floor — including the $500 fee cap, no special-use-permit requirement, and no family-relation rule — beginning July 1, 2027.
Is Your Arlington County Property Eligible for an ADU?
Use our free eligibility checker to find out in about a minute, and get a personalised report sent to your inbox.