Yes: Alexandria allows one accessory dwelling per lot on any lot with a single-unit, two-unit or townhouse dwelling, citywide, under Zoning Ordinance Sec. 7-203 (adopted 2021). Since June 14, 2025 (Ord. No. 5593) there is no separate ADU permit and no owner-occupancy rule: you apply straight for a building permit. An ADU inside the house may be up to one-third of the house's gross floor area; a detached ADU's first floor is capped at the greater of one-third of the house's first floor or 350 sq ft (lots of 2,500 sq ft or less) / 500 sq ft (larger lots), with a 20 ft height limit and 1 ft side/rear setbacks (3 ft where windows face the line). No parking is required. Short-term rental of an ADU is allowed with a city STR permit (Sec. 7-1400, since Sept 1, 2025).
Zoning & Size Requirements [1][2][3][4][5][6][7]
Yes — Alexandria allows ADUs. The size limit is a formula rather than one figure — see the size rule in the table below — under current Virginia and Alexandria zoning rules.
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| Allowed Zones | Citywide: an accessory dwelling is a permitted accessory use on any recorded lot developed with a single-unit, two-unit or townhouse dwelling (Sec. 7-101(N), 7-203(B)(1)); no zoning district is excluded. Exterior work in the Old and Historic Alexandria or Parker-Gray districts also needs a Board of Architectural Review approval under Article X (BAR fees in the FY2027 P&Z schedule). 96 ADUs approved from 2021 to Feb 20, 2026 (city Zoning for Housing implementation page). |
| Max Size (Detached) | First floor of the detached accessory building may not exceed the greater of (a) one-third of the floor area of the principal dwelling's first floor or (b) 350 sq ft on lots of 2,500 sq ft or less / 500 sq ft on lots larger than 2,500 sq ft (Sec. 7-203(C)(1)). Only the first floor is capped; an upper floor is allowed within the 20 ft height limit. For this test, floor area includes space otherwise excluded by Sec. 2-145(A)(12)/(B)(14). |
| Max Size (Attached) | An accessory dwelling within the principal dwelling may not exceed one-third of the principal dwelling's gross floor area (Sec. 7-203(B)(3)). No fixed square-foot cap; the house's own FAR/lot-coverage limits for the zone still apply. |
| Max Size (JADU) | Not a category in Alexandria; a small interior unit is simply an accessory dwelling under Sec. 7-203 (one-third of the house's gross floor area cap). Guest houses without a kitchen are a separate accessory use (Sec. 7-101). |
| Max Height | Detached accessory building: the lesser of the principal dwelling's height or 20 ft, measured to include rooftop appurtenances listed in Sec. 6-403(B) (Sec. 7-203(C)(2)). |
| Max Units | One accessory dwelling per recorded lot, including lots subject to Sec. 7-103(D) (Sec. 7-203(B)(2)). The former three-person occupancy cap was deleted by Ord. No. 5593 (June 14, 2025); the building code governs occupancy. |
Setback Requirements [1][2][3][4][5][6][7]
Alexandria requires a rear setback of about 1 ft for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is not required — you can rent it out without living on the property.
| Rear Setback | Detached ADU building allowed in the required rear yard: at least 1 ft from the rear lot line including architectural features (unless the zone requires less); 3 ft if a wall with windows or doors faces that line; 2.5 ft for portions taller than 13.5 ft and under 16 ft; 5 ft for portions over 16 ft; and, outside the historic districts, 5 ft including overhang where a neighbor's window or door sill under 20 ft high sits within 3 ft of the shared line (Sec. 7-203(C)(3)). |
| Side Setback | Same rule as the rear yard (Sec. 7-203(C)(3)): 1 ft minimum including architectural features; 3 ft where windows or doorways face the nearest side lot line; 2.5 ft for portions 13.5-16 ft tall; 5 ft for portions over 16 ft; 5 ft including overhang opposite a neighbor's low window or door within 3 ft of the shared line (outside the Old and Historic Alexandria and Parker-Gray districts). |
| Front Setback | A detached ADU building is a permitted obstruction in any yard except a front yard (Sec. 7-202(C)) and no accessory structure may sit forward of the front building wall facing a primary front yard (Sec. 7-103); the zone's front-yard setback applies. Building an ADU forward of the house needs a BZA variance (BZA #2025-00012 was such a request). |
| Parking Required | None. An accessory dwelling is exempt from providing off-street parking (Sec. 7-203(C)(4)). A short-term-rental permit for the ADU carries its own parking test under Sec. 7-1403(C). |
| Owner Occupancy | Not required. The 2021 rule that the owner live on the property when the ADU permit was issued (former Sec. 7-203(B)(6)) was deleted by Ord. No. 5593, final passage June 14, 2025. The ADU and principal dwelling must stay under common ownership (Sec. 7-203(B)(5)); the ADU cannot be sold separately. |
| Min Lot Size | None ADU-specific. The 2,500 sq ft figure is only the tier line for the 350 vs 500 sq ft detached footprint cap (Sec. 7-203(C)(1)). The lot must meet its zone's own standards for the principal dwelling; Sec. 2-141 says the ADU does not count toward the zone's density, open-space or lot requirements. |
Permit Process & Fees [8][9][10]
An ADU permit in Alexandria goes through a standard permit review. Review time: not published. The city posts no residential plan-review time; only a 20-minute walk-thru review is listed for minor work such as finishing a basement (Plan Review Services Division page). Historic-district projects add a BAR hearing cycle. Permit fees: No separate ADU permit since June 2025 (a $135 ADU zoning-permit line remains in the FY2027 P&Z schedule; confirm). Building permit: new construction $0.75/sq ft plus $194 each electrical, plumbing, mechanical; alterations $0.30/sq ft ($95 min); plus 5% tech fee and state levy (FY26 schedule).
| Approval Process | Building permit through the Permit Center (APEX) with Planning & Zoning sign-off on the Sec. 7-203 standards; the separate Planning & Zoning ADU permit was abolished by Ord. No. 5593 (June 14, 2025). Add a BAR Certificate of Appropriateness for exterior work in the Old and Historic Alexandria or Parker-Gray districts, and a BZA special exception (Sec. 11-1302(F)) to expand a pre-Feb 20, 2021 noncomplying accessory building for an ADU. |
| Review Timeline | Not published. The city posts no residential plan-review time; only a 20-minute walk-thru review is listed for minor work such as finishing a basement (Plan Review Services Division page). Historic-district projects add a BAR hearing cycle. |
| Permit Fees | No separate ADU permit since June 2025 (a $135 ADU zoning-permit line remains in the FY2027 P&Z schedule; confirm). Building permit: new construction $0.75/sq ft plus $194 each electrical, plumbing, mechanical; alterations $0.30/sq ft ($95 min); plus 5% tech fee and state levy (FY26 schedule). |
| Impact Fees | None. Neither the FY2027 Planning & Zoning fee schedule nor the FY26 Code Administration schedule contains an impact or capacity fee; Virginia localities do not levy development impact fees on ADUs. Utility connection charges are set separately by the water and sewer utilities. |
| Plan Check | Included in the building permit fee (initial review plus one corrected resubmission); optional Accelerated Plan Review at $0.045/sq ft for new residential construction or $0.075/sq ft for alterations (FY26 Code Administration schedule, sec. C). |
| Pre-Approved Plans | Not available. No pre-approved or stock ADU plan program appears on the city's ADU page, the APEX document library or the FY2027 fee schedule. |
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Construction Costs [11][12][13]
Building an ADU in Alexandria typically costs $150,000-$350,000 ($200-$400 per sq ft); a garage conversion runs $80,000-$150,000.
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| Average Build Cost | $150,000-$350,000 |
| Cost per Sq Ft | $200-$400 |
| Garage Conversion | $80,000-$150,000 |
| Prefab ADU (Installed) | $150,000-$300,000 |
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Rental Income Potential [14][15]
A 2-bedroom ADU in Alexandria rents for around $2,300-$3,500/mo, an estimated 7-14% gross annual return.
| Avg Rent (1 Bedroom) | $2,100-$3,150/mo |
| Avg Rent (2 Bedroom) | $2,300-$3,500/mo |
| Short-Term Rental | Allowed with a city short-term rental permit (Sec. |
| Est. Annual ROI | 7-14% gross annual return |
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Recent Law Changes
What's Changed Recently
- 2026-09-20 re-verification: every standard re-traced to the adopted ordinance text (Text Amendment 2020-00007 implementing ordinance, final passage March 13, 2021) and the two later amendments below; the entry's old owner-occupancy, '70-100 days', 'ADU permit ~$75-100' and '$1,200-$2,000 impact fee' claims were wrong or unsourced and are corrected
- Ord. No. 5593 (Text Amendment 2025-00003, approved May 17, 2025, final passage June 14, 2025) deleted the separate Planning & Zoning ADU permit (former Sec. 7-203(A)), the owner-occupancy-at-permit requirement (former (B)(6)) and the three-person occupancy cap in (B)(4); ADUs now go straight to a building permit
- Short-term rental ordinance (Text Amendment 2024-00011, approved Feb 22, 2025, final passage March 15, 2025, effective Sept 1, 2025) repealed the 120-day cap on renting an ADU short-term (former Sec. 7-203(B)(7)) and added Sec. 7-1400: STR permit for rentals over 10 days a year, ADU occupancy capped at 3, no simultaneous STR of house and ADU
- Zoning for Housing (adopted Nov 28, 2023) only re-worded Sec. 7-203(B)(1) to 'single-unit, two-unit or townhouse'; the ADU standards come from the separate 2021 ordinance and are not part of the court challenge to the 2023 package (city reports 96 ADU approvals to Feb 20, 2026)
- Virginia SB 531 (Acts of Assembly Ch. 895, approved April 13, 2026, effective July 1, 2027) does not apply to Alexandria: Sec. 15.2-2292.4(I) exempts any locality that adopted an ADU ordinance before Jan 1, 2026, and Alexandria's dates from 2021; the local Sec. 7-203 rules continue unchanged unless Council amends them
- FY2027 Planning & Zoning fee schedule effective July 1, 2026 (BAR residential new building $1,375 + $1.15/sq ft; addition or accessory structure of 250 sq ft or more $1,185 + $1.15/sq ft; BZA special exception $335); Code Administration building-permit rates are the FY26 schedule effective July 1, 2025
Tips for Building an ADU in Alexandria
- Size worked example: a 1,200 sq ft first-floor house on a 6,000 sq ft lot may have a detached ADU with a 500 sq ft first floor (the greater of 400 sq ft or 500 sq ft); on a 2,400 sq ft lot the floor is 350 sq ft. A second floor is allowed under the 20 ft height cap, so total ADU floor area can exceed the footprint (Sec. 7-203(C)(1)-(2))
- Floor area for the lot's FAR: ADU space inside an accessory building is excluded from the lot's floor area up to 100 sq ft (lots under 2,500 sq ft), 350 sq ft (2,500 sq ft or more) or 600 sq ft (8,000 sq ft or more) in the R-20, R-12, R-8, R-5, R-2-5 zones and single/two-unit lots in RA and RB outside the historic districts, shared with the garage and shed exclusions (Sec. 2-145(A)(12)); elsewhere the exclusion is 65 sq ft (Sec. 2-145(B)(14))
- Setback planning: keep any wall with a window or door at least 3 ft from the side or rear line, keep parts of the building taller than 16 ft at least 5 ft back, and check the neighbor's windows: outside the historic districts a neighbor's window or door with a sill under 20 ft within 3 ft of the shared line forces a 5 ft setback including your roof overhang along that stretch (Sec. 7-203(C)(3))
- Existing garage or carriage house that already breaks the Sec. 7-203(C) rules and existed before Feb 20, 2021: you can expand or rebuild it for an ADU with a BZA special exception under Sec. 11-1302(F) as long as the noncompliance does not get worse (residential variance/special exception fee $335 in the FY2027 P&Z schedule)
- Permit path since June 2025: there is no Planning & Zoning ADU permit, affidavit or deed recordation; submit construction drawings in APEX and zoning reviews Sec. 7-203 compliance with the building permit. If the FY2027 schedule's $135 'Accessory Dwelling Unit Zoning Administrative Permit' line is charged, ask staff which permit it attaches to, because Sec. 7-203(A) is now 'Reserved'
- Historic districts (Old and Historic Alexandria, Parker-Gray): a new detached ADU needs a BAR Certificate of Appropriateness; FY2027 BAR fees are $1,375 + $1.15/sq ft for a new residential building and $1,185 + $1.15/sq ft for an addition or accessory structure of 250 sq ft or more, $150 under 250 sq ft. Check the 2026 BAR hearing schedule for filing deadlines
- Renting: no owner-occupancy rule and no minimum lease term apply to a long-term ADU rental; a short-term rental needs the Sec. 7-1400 permit, allows at most 3 guests in an ADU, and you cannot list the main house and the ADU as STRs at the same time
- Rent reference: HUD FY2027 Small Area Fair Market Rents (effective Oct 1, 2026) for Alexandria city ZIPs run $2,090 (22311) to $3,150 (22314) for a 1-bedroom and $2,310 to $3,480 for a 2-bedroom; Old Town (22314) and Del Ray/Rosemont (22301) are the top of the range
- Cost basis: Northern Virginia builder guides dated March-June 2026 that name Alexandria put a turnkey detached ADU at $150,000-$250,000 (400-800 sq ft) and $200,000-$350,000+ for larger new builds, at roughly $200-$275/sq ft economy to $375-$500+/sq ft high-end; garage conversions $80,000-$150,000; basement ADUs $60,000-$145,000. Historic-district finishes and small footprints push Alexandria toward the top of these ranges
- Cost basis (2026-09-20 re-verification): short term allowed: Allowed with a city short-term rental permit (Sec. 7-1400, effective Sept 1, 2025) when rented more than 10 days a year; ADU occupancy capped at 3 guests; the house and the ADU may not both be listed as STRs at the same time (Sec. 7-1403(F)). The old 120-day ADU limit was repealed.
ADU Builders in Alexandria
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Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Ordinance implementing Text Amendment No. 2020-00007 (Accessory Dwelling Units), adding Sec. 7-203 — City of Alexandria (Legistar file 21-0682, final passage March 13, 2021) ordinance — Accessed 2026-09-20
- Ordinance No. 5593 (Text Amendment No. 2025-00003), amending Sec. 7-203 to delete the ADU permit and use limitations — signed ordinance, final passage June 14, 2025 ordinance — Accessed 2026-09-20
- Zoning Text Amendment #2025-00003 Staff Report (rationale for deleting the ADU permit and owner-occupancy) — Planning & Zoning, May 2025 Planning Department — Accessed 2026-09-20
- Zoning for Housing 2023 draft text amendment, Article VII (Sec. 7-203(B)(1) wording change) — City of Alexandria Planning Department — Accessed 2026-09-20
- Accessory Dwelling Units in Alexandria — City of Alexandria Planning Department — Accessed 2026-09-20
- Zoning for Housing Implementation (96 ADU approvals to Feb 20, 2026) — City of Alexandria Planning Department — Accessed 2026-09-20
- Virginia SB 531 — Acts of Assembly Chapter 895 (2026), Code § 15.2-2292.4 (the act numbered it 2292.3; codified as 2292.4), effective July 1, 2027 Government Data — Accessed 2026-09-20
- FY2027 Planning and Zoning Fee Schedule, effective July 1, 2026 — City of Alexandria fee_schedule — Accessed 2026-09-20
- FY26 Code Administration / Alexandria Permit Center Fee Schedule, effective July 1, 2025 fee_schedule — Accessed 2026-09-20
- Plan Review Services Division — Department of Code Administration Planning Department — Accessed 2026-09-20
- Excell Homes — How Much Does an ADU Cost in Northern Virginia? (2026 breakdown; names Alexandria; updated June 30, 2026) industry — Accessed 2026-09-20
- Renewal Homes DMV — Accessory Dwelling Units in Virginia: 2026 Guide (June 18, 2026) industry — Accessed 2026-09-20
- DC Structures — Virginia ADUs (prefab/kit pricing, updated Jan 5, 2026) industry — Accessed 2026-09-20
- HUD FY2027 Small Area Fair Market Rents — Washington-Arlington-Alexandria, DC-VA-MD HUD Metro FMR Area, ZIPs 22301-22314 Government Data — Accessed 2026-09-20
- Short-term residential rental ordinance (Text Amendment No. 2024-00011), deleting Sec. 7-203(B)(7) and adding Sec. 7-1400 — final passage March 15, 2025, effective Sept 1, 2025 ordinance — Accessed 2026-09-20
Frequently Asked Questions
Can I build an ADU in Alexandria?
Yes. ADUs are allowed in Citywide: an accessory dwelling is a permitted accessory use on any recorded lot developed with a single-unit, two-unit or townhouse dwelling (Sec. 7-101(N), 7-203(B)(1)); no zoning district is excluded. Exterior work in the Old and Historic Alexandria or Parker-Gray districts also needs a Board of Architectural Review approval under Article X (BAR fees in the FY2027 P&Z schedule). 96 ADUs approved from 2021 to Feb 20, 2026 (city Zoning for Housing implementation page). in Alexandria. The maximum size for a detached ADU is First floor of the detached accessory building may not exceed the greater of (a) one-third of the floor area of the principal dwelling's first floor or (b) 350 sq ft on lots of 2,500 sq ft or less / 500 sq ft on lots larger than 2,500 sq ft (Sec. 7-203(C)(1)). Only the first floor is capped; an upper floor is allowed within the 20 ft height limit. For this test, floor area includes space otherwise excluded by Sec. 2-145(A)(12)/(B)(14).. Owner-occupancy is not required, so you can rent out the ADU.
How much does an ADU cost in Alexandria?
ADU construction in Alexandria typically costs $150,000-$350,000. Garage conversions run $80,000-$150,000, and prefab ADUs cost $150,000-$300,000.
How much can I rent an ADU for in Alexandria?
Average ADU rents in Alexandria are $2,100-$3,150/mo for a 1-bedroom and $2,300-$3,500/mo for a 2-bedroom unit.
Do I need parking for an ADU in Alexandria?
None. An accessory dwelling is exempt from providing off-street parking (Sec. 7-203(C)(4)). A short-term-rental permit for the ADU carries its own parking test under Sec. 7-1403(C).. Check with Alexandria planning department for the latest Virginia ADU parking rules, as many states have relaxed requirements in recent years.
How long does it take to get an ADU permit in Alexandria?
Alexandria does not publish a standard ADU review timeline. The city posts no residential plan-review time; only a 20-minute walk-thru review is listed for minor work such as finishing a basement (Plan Review Services Division page). Historic-district projects add a BAR hearing cycle. Permit fees: No separate ADU permit since June 2025 (a $135 ADU zoning-permit line remains in the FY2027 P&Z schedule; confirm). Building permit: new construction $0.75/sq ft plus $194 each electrical, plumbing, mechanical; alterations $0.30/sq ft ($95 min); plus 5% tech fee and state levy (FY26 schedule).
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