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Alexandria, VA Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

ADU rules in Alexandria, VA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Eligible lots: Single-unit, two-unit, or townhouse dwellings only
ADUs per lot: One accessory dwelling per recorded lot
Detached ADU max size: 1/3 of home's 1st floor, or 350-500 sq ft
Max height: Lesser of home's height or 20 feet
Min side/rear setback: 1 foot, more for taller or windowed walls
Off-street parking: Not required for the ADU itself

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Virginia under recent ADU streamlining laws. The Alexandria, VA rules below cover local size, height, and setback requirements.

Summary

Alexandria's Zoning Ordinance lets homeowners add one accessory dwelling unit to a single-unit, two-unit, or townhouse property under Section 7-203. A detached ADU tops out at one-third of the principal home's first-floor area or 350 to 500 square feet, whichever is greater, capped at 20 feet in height, with no off-street parking required.

(B)Use limitations.(1)An accessory dwelling shall be permitted as an accessory use to a single-unit, two-unit, or townhouse dwelling only.(2)Only one accessory dwelling shall be permitted on any recorded lot including properties subject to section 7-103(D).(3)The gross floor area of an accessory dwelling within a principal dwelling shall not exceed one-third of the principal dwelling's gross floor area.(5)The accessory and principal dwelling shall remain under common ownership.(C)Bulk and setback requirements for a detached accessory building...(1)Size. The maximum floor area of the accessory building's first floor shall not exceed the greater of:(a)One-third of the floor area of the principal dwelling's first floor; or(b)Three hundred fifty square feet for lots 2,500 square feet or less and 500 square feet for lots larger than 2,500 square feet.(2)Height. The maximum height of the accessory building shall not exceed the lesser of the following:(a)The height of the principal dwelling; or(b)Twenty feet.

View official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 156 | Zoning: Supplement 103).

Full Breakdown

Section 7-203(B) limits an accessory dwelling to lots holding a single-unit, two-unit, or townhouse dwelling, with only one accessory dwelling allowed per recorded lot no matter how many principal units already sit there. If the ADU is built inside the main house, its floor area cannot exceed one-third of the principal dwelling's gross floor area, and its kitchen must include a sink, cooking appliance, food-preparation counter, storage cabinets, and a refrigerator. A detached accessory building housing the ADU is capped, under Section 7-203(C), at the greater of one-third of the principal dwelling's first-floor area or 350 square feet on lots of 2,500 square feet or less (500 square feet on larger lots), and its height cannot exceed the lesser of the principal dwelling's height or 20 feet, including rooftop appurtenances.

5 and 16 feet tall and five feet for anything taller. Section 7-203(B)(5) requires the accessory dwelling and the principal dwelling to stay under common ownership, and Section 7-203(D) exempts the ADU from the off-street parking rules that apply to other residential uses, though garage access is still governed by Section 7-2501(B)(3).

Violations & Fines

An accessory dwelling built or used outside these limits is a use, height, or coverage violation of the zoning ordinance under Section 11-207(A), punishable as a class five civil violation: $200 for a first offense and $500 for each later violation of the same requirement, up to $5,000 total for a repeated series arising from the same facts. The director can also issue a written notice under Section 11-204 ordering the illegal structure or use corrected within ten days before pursuing court action to restrain or abate it.

Frequently Asked Questions

Can I build an ADU on any residential lot in Alexandria?

Only if the lot holds a single-unit, two-unit, or townhouse dwelling, per Section 7-203(B)(1). Multi-unit apartment lots do not qualify, and only one accessory dwelling is allowed per recorded lot regardless of how many principal units already sit there.

How tall can a detached ADU be in Alexandria?

Section 7-203(C)(2) caps it at the lesser of 20 feet or the height of the principal dwelling, measured to include rooftop appurtenances covered by Section 6-403(B). A one-story main house limits the detached ADU to that same lower height.

Does my Alexandria ADU need its own parking space?

No. Section 7-203(D) exempts accessory dwellings from the off-street parking requirements that apply to other residential uses, though access to a garage-based ADU is still governed by Section 7-2501(B)(3).

Can I sell my Alexandria ADU separately from the main house?

No. Section 7-203(B)(5) requires the accessory dwelling and the principal dwelling to remain under common ownership, so the ADU cannot be subdivided off or sold apart from the main property while it operates as an accessory dwelling.

Sources & Official References

[1]Alexandria Zoning Ordinance § 7-203, Accessory Dwellings

Other rules in Alexandria

Fence Regulations: Height LimitsSome Restrictions Shed & Carport RulesSome Restrictions Parking Rules: RV & Boat ParkingSignificant Restrictions Parking Rules: Driveway RulesSome Restrictions Fence Regulations: Retaining WallsSome Restrictions Animal Ordinances: Pet Groomer RulesSome Restrictions Landscaping Rules: Tree Removal & Heritage TreesSome Restrictions

All Alexandria rules

How Alexandria compares: Easiest Cities to Build an ADU·Compare Alexandria to another location·View the Virginia accessory structures overview

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