Build Your ADU in City of Alexandria, VA
Design, permits and construction of accessory dwelling units, built to City of Alexandria’s rules by a contractor that builds nothing else.
- ADU max size
- The greater of one third of the house floor area, or 350 sq ft on lots up to 2,500 sq ft and 500 sq ft on larger lots
- Minimum lot size
- No minimum
- Owner occupancy
- Required
- Off-street parking
- The lot must have at least two off-street driveway spaces
- Allowed by
- Right, in permitted zones
- Rules current as of
- 2021-12-01
Can you build an ADU in the City of Alexandria, VA?
City of Alexandria ADU Guidelines
The rules that decide whether, and what, you can build. The table below carries the specifics.
Up to 500 Sq Ft Detached
For detached ADUs, the maximum first-floor footprint is 350 sq ft on lots of 2,500 sq ft or less, and 500 sq ft on larger lots — or one-third of the primary home's first-floor area, whichever is greater. Attached interior ADUs cannot exceed one-third of the principal dwelling's total gross floor area.
Citywide — All R Zones
ADUs are permitted as an accessory use to single-unit, two-unit, or townhouse dwellings throughout Alexandria. Only one ADU is allowed per recorded lot. An administrative permit from the Department of Planning & Zoning is required — staff review is completed within 10 business days of a complete application.
As Low as 1 Foot
Alexandria has some of the most flexible setbacks in the region. Detached ADUs require just a 1-foot setback from side and rear lot lines — increasing to 3 feet if the wall has windows or doors. Portions exceeding 13.5 ft in height require 2.5 ft setbacks, and portions above 16 ft require 5 ft setbacks.
Up to 20 Feet
The detached ADU cannot exceed the lesser of 20 feet or the height of the primary dwelling. Note that height thresholds of 13.5 ft and 16 ft trigger increased setback requirements, so taller ADUs need to be sited carefully on the lot. All rooftop appurtenances count toward the height calculation.
Live on Site Required
The property owner must maintain the property as their primary residence at the time the ADU permit is issued. Long-term rentals of the ADU are permitted. Short-term rentals (e.g., Airbnb) are allowed for up to 120 days per calendar year — but the main house and ADU cannot both be short-term rented simultaneously.
No Parking Required
Alexandria exempts ADUs from any off-street parking requirement — a major advantage over many neighboring jurisdictions. No existing required parking spaces may be removed to accommodate ADU construction, but no new space needs to be added either. This makes ADUs viable on nearly any lot in the city.
| Requirement | Alexandria Standard (Zoning Ordinance §7-203) |
|---|---|
| Detached ADU footprint — lots ≤ 2,500 sq ft | 350 sq ft maximum |
| Detached ADU footprint — lots > 2,500 sq ft | 500 sq ft maximum (or 1/3 of primary home's first-floor area, whichever is greater) |
| Attached / interior ADU size | Up to 1/3 of the principal dwelling's gross floor area |
| Units allowed per lot | One ADU per recorded lot |
| Eligible properties | Single-unit, two-unit, and townhouse dwellings citywide |
| Side & rear setback | 1 ft minimum (3 ft where the wall has windows or doors) |
| Maximum height | Lesser of 20 ft or the primary dwelling's height (larger setbacks required above 13.5 ft and 16 ft) |
| Off-street parking | None required |
| Maximum occupants | 3 persons (one family) |
| Owner occupancy | Required — owner must reside in main house or ADU; units stay in common ownership |
| Short-term rental | Permitted within city limits; main house and ADU cannot both be short-term rented at once; no exclusive STR use |
| Historic districts (Old Town, Parker-Gray) | Board of Architectural Review (BAR) approval required — adds review time |
| Approval path | Administrative ADU permit (Planning & Zoning, ~10 business days) + building permit (Code Administration) |
| Typical build time | Move-in ready in as little as 120 days from permit approval |
Regulations summarized from the City of Alexandria accessory dwelling unit program and Zoning Ordinance §7-203 (ADU policy adopted January 23, 2021). Last verified August 2026. Zoning rules change — confirm current requirements with the City of Alexandria before finalizing your project.
The City of Alexandria ADU Permit Process
- 01
Zoning & Eligibility Check
Confirm lot size, setback options, and size limits. Makara ADU does this free with our property eligibility checker — results in seconds.
- 02
ADU Permit Application
Submit administrative permit application to Alexandria's Dept. of Planning & Zoning via the APEX portal. Staff review completed within 10 business days.
- 03
Building Permit & Design
After ADU permit approval, a full building permit with architectural plans is filed with the Dept. of Code Administration. Trades permits (electrical, plumbing, mechanical) follow.
- 04
Build & Certificate
Construction, city inspections, and certificate of occupancy — your ADU is ready to occupy or rent to long-term or (within limits) short-term tenants.
City of Alexandria’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.
Alexandria-Specific Knowledge
We know the nuances of Alexandria's two-step permitting process — the ADU permit through Planning & Zoning and the building permit through Code Administration. We know which neighborhoods have unique flooding, density, or historic district constraints, and how to design around them.
One Contractor, Start to Finish
Architecture, both permit applications, foundation, framing, MEP, finishes — Makara ADU manages everything under one contract. No juggling separate architects, engineers, and builders across a two-agency permitting process.
Fixed-Price Proposals
We quote your Alexandria project in full before construction begins. Alexandria's small urban lots require precise planning around setbacks, height, and existing structures — we design for every constraint upfront so there are no surprises.
Built for Every Reason
Aging parents nearby, adult children returning home, rental income to offset a mortgage, or a private home office — Makara ADU designs flexible spaces that serve your life now and adapt as needs change. We design for the long term, not just the permit.
ADU Types We Build in City of Alexandria
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 City of Alexandria 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 |
City of Alexandria ADU FAQ
Can I build an ADU in the City of Alexandria, VA?
Yes. Alexandria permits one ADU per lot on single-unit, two-unit, and townhouse properties citywide, under Zoning Ordinance §7-203. ADUs may be detached, attached, or interior conversions, and are approved through an administrative permit from the Department of Planning & Zoning.
How big can an ADU be in Alexandria?
A detached ADU's first-floor footprint is capped at 350 sq ft on lots of 2,500 sq ft or less and 500 sq ft on larger lots, or one-third of the primary home's first-floor area, whichever is greater. An attached or interior ADU cannot exceed one-third of the principal dwelling's gross floor area.
What are the setback and height rules for an Alexandria ADU?
Detached ADUs require just a 1-foot side and rear setback, increasing to 3 feet where the wall has windows or doors. Height is capped at the lesser of 20 feet or the primary home's height, with larger setbacks required above 13.5 feet and 16 feet.
Does Alexandria require off-street parking for an ADU?
No. Alexandria exempts ADUs from any off-street parking requirement, though existing required parking for the main home cannot be removed to build the ADU. This makes ADUs feasible on nearly any lot in the city.
Do I have to live on the property to have an ADU in Alexandria?
Yes. Alexandria requires owner-occupancy — the owner must reside in either the main house or the ADU at the time the ADU permit is issued. The ADU and main house must remain in common ownership and cannot be sold separately.
Can I rent out my Alexandria ADU or use it for Airbnb?
Long-term rental is permitted. Short-term rental is allowed only within the city's limits, and the main house and the ADU cannot both be short-term rented at the same time — exclusive short-term rental use of the ADU is prohibited.
What about ADUs in Old Town or other Alexandria historic districts?
ADUs in the Old and Historic Alexandria and Parker-Gray districts require Board of Architectural Review (BAR) approval on top of the standard ADU and building permits. This design review adds time, so historic-district projects should plan for a longer permitting timeline.
How much does an Alexandria ADU cost, and how long does it take?
A turnkey detached ADU in Alexandria typically runs from about $250,000 to $300,000 depending on size, site, and finishes; conversions cost less. The administrative ADU permit is reviewed in about 10 business days, and a Makara ADU can be move-in ready in as little as 120 days from permit approval.
Is Your City of Alexandria 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.