Arlington County allows one accessory dwelling (AD) on any lot with a one-family detached house in the R-20, R-10, R-8, R-6, R-5, R-10T, R-15-30T and R2-7 districts, through an Accessory Dwelling Permit issued by the Zoning Administrator under Zoning Ordinance §12.9.2 - no public hearing. An AD is capped at 750 sq ft and 35% of the combined floor area (500 sq ft and 45% if the house is under 1,000 sq ft); a basement AD has no size cap. A new detached AD building is limited to 1.5 stories/25 ft, a 560 sq ft footprint in R-5/R-6 (650 sq ft elsewhere), 5 ft side and rear setbacks, 25 ft from any street and 8 ft from the house. The owner must live in either unit, record a covenant, and file an affidavit of compliance; the AD Permit fee is $582 (FY2027) plus building-permit fees of $1.70 per sq ft for new construction. Virginia's 2026 ADU law (SB 531, effective July 1, 2027) does not apply to Arlington because its AD ordinance predates 2026.
Zoning & Size Requirements [1][2][3][4][5]
Yes — Arlington allows ADUs. A detached ADU can typically be up to 750 sq ft under current Virginia and Arlington zoning rules.
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| Allowed Zones | R-20, R-10, R-8, R-6, R-5, R-10T, R-15-30T and R2-7 districts, on a lot with a one-family detached dwelling (§12.9.2; county AD Permit page). ADs may also be within or attached to semidetached/townhouse dwellings built under the Expanded Housing Option, §10.4. Not allowed on a lot that already has a family/caregiver suite (§12.9.2.A.1(a)). ADs are allowed by permit of the Zoning Administrator; no County Board hearing. |
| Max Size (Detached) | Gross floor area capped at the lesser of 750 sq ft or 35% of the combined floor area of house plus AD when the house is at least 1,000 sq ft; 500 sq ft or 45% when the house is under 1,000 sq ft (§12.9.2.A.2(e)). A detached accessory building approved after May 18, 2019 may hold an AD only if its footprint is 560 sq ft or less in R-5/R-6, 650 sq ft or less in the other R districts (§12.9.2.A.2(d)). GFA counts attic and basement space (§3.1.1). |
| Max Size (Attached) | Same 750 sq ft/35% (or 500 sq ft/45%) cap as detached for any AD with space above the basement; an AD wholly within a basement has no size cap other than the basement's perimeter walls (§12.9.2.A.2(e)(1)). |
| Max Size (JADU) | Not a category in Arlington. The separate 'family/caregiver suite' permit ($603 zoning fee, FY2027) is for relatives or caregivers only and cannot coexist with an AD on the same lot (§12.9.2.A.1(a)). |
| Max Height | A detached accessory building approved after May 18, 2019 that contains an AD may not exceed 25 ft or 1.5 stories, whichever is less (§12.9.2.A.2(c)). Existing pre-May 2019 accessory buildings converted with interior-only alterations carry no AD-specific height limit (§12.9.2.A.2(a)). ADs inside the house follow the main-dwelling height for the district. |
| Max Units | One accessory dwelling per lot (§12.9.2.A.1(b)); no AD where a family/caregiver suite exists. The AD may be occupied by no more than three persons (§12.9.2.C.2). |
Setback Requirements [1][2][3][4][5]
Arlington requires a rear setback of about 5 ft for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is required.
| Rear Setback | New detached AD building: 5 ft to the wall on interior lots; 10 ft to the eave on corner lots (§12.9.2.A.2(b)). The general §3.2.6 rule that no accessory building may be closer than 8 ft to any wall of the main dwelling also applies. |
| Side Setback | New detached AD building: 5 ft to the wall on interior and corner lots (§12.9.2.A.2(b)(1)-(2)). |
| Front Setback | The nearest wall of a detached building containing an AD must be at least 25 ft from any street or designated right-of-way line (§12.9.2.A.2(b)(3)) and at least 8 ft from any wall of the main dwelling (§3.2.6). No exterior stairs to an above-first-floor AD entrance on the street-facing side of the lot (§12.9.2.A.2(f)). |
| Parking Required | No new space is required if the lot already has one or more off-street spaces - existing spaces must be kept (1 or 2 kept; at least 2 kept if more exist). A lot with no off-street parking must add one space unless a County parking survey finds the block less than 65% parked (§14.3 table; $387 DES parking-survey fee, FY2027). |
| Owner Occupancy | Required: the owner of the main dwelling must occupy either the main dwelling or the AD as their primary residence; otherwise the whole property may be occupied by only one family (§12.9.2.C.3). A covenant is recorded before the building permit; an affidavit of compliance is filed before the certificate of occupancy and again on any structural change or sale (§12.9.2.C.1, C.4). SB 531 (2026) does not change this: Code §15.2-2292.4(I) exempts localities whose ADU ordinance predates Jan 1, 2026. |
| Min Lot Size | No AD-specific minimum lot size. Eligibility is by zoning district (R-20 through R2-7) plus a one-family detached dwelling; the AD and any new detached building must meet the district's Article 3 and Article 5 coverage and dimensional standards (§12.9.2.A.2). A nonconforming house or accessory building may still be used, per Article 16. |
Permit Process & Fees [6][7][8]
An ADU permit in Arlington goes through a standard permit review. Typical timeline: About 30 days for the AD Permit once the Zoning Division accepts the application as complete (county AD Permit page); the county recommends filing it at least two weeks before the building-permit application. No published review time for the residential building permit. Permit fees: AD Permit $582 plus $387 if a DES parking survey is needed (FY2027 Planning and Zoning fee schedule, effective July 1, 2026). Building permit $1.70 per sq ft for new construction/additions or $0.63 per sq ft for alterations, plus a 2% state levy and a 10% automation surcharge; CO for an AD $520.
| Approval Process | Two permits: (1) an Accessory Dwelling Permit from the Zoning Division, filed in Permit Arlington as a 'Zoning Application' with floor plans, a certified plat, a site plan, the Acknowledgement and Agreement, and the Declaration of Covenants; the Zoning Administrator signs it - no hearing. (2) A Residential Building Permit plus trade permits from Inspection Services (ISD), which cannot issue until the AD Permit is issued and the covenant is recorded. Zoning and ISD inspect; an Affidavit of Compliance precedes the Certificate of Occupancy. |
| Review Timeline | About 30 days for the AD Permit once the Zoning Division accepts the application as complete (county AD Permit page); the county recommends filing it at least two weeks before the building-permit application. No published review time for the residential building permit. |
| Permit Fees | AD Permit $582 plus $387 if a DES parking survey is needed (FY2027 Planning and Zoning fee schedule, effective July 1, 2026). Building permit $1.70 per sq ft for new construction/additions or $0.63 per sq ft for alterations, plus a 2% state levy and a 10% automation surcharge; CO for an AD $520. |
| Impact Fees | None. Arlington charges no development impact or capacity fee for an accessory dwelling; costs are limited to permit, plan-review and trade-permit fees and any utility connection charges from the Department of Environmental Services. |
| Plan Check | Zoning reviews the AD Permit and the building permit for §12.9.2, §3.2 and §14.3 compliance ($260 zoning review for a detached garage/accessory structure or $384 for an interior alteration to a one-family dwelling, FY2027); ISD reviews to the Virginia Uniform Statewide Building Code. Trade permits: electrical minimum $186, mechanical $149, plumbing $149. |
| Pre-Approved Plans | Not available |
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Construction Costs [9][10][11][12]
Building an ADU in Arlington typically costs $150,000-$350,000 ($200-$400 per sq ft); a garage conversion runs $80,000-$160,000.
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| Average Build Cost | $150,000-$350,000 |
| Cost per Sq Ft | $200-$400 |
| Garage Conversion | $80,000-$160,000 |
| Prefab ADU (Installed) | $150,000-$300,000 |
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Rental Income Potential [13][14]
A 2-bedroom ADU in Arlington rents for around $2,300-$3,700/mo, an estimated 7-14% gross annual return.
| Avg Rent (1 Bedroom) | $2,100-$3,300/mo |
| Avg Rent (2 Bedroom) | $2,300-$3,700/mo |
| Short-Term Rental | Allowed only as an 'accessory homestay' with a separate one-year permit ($113 zoning fee): the host must live on the property at least 185 days a year, may rent the main house, the AD or both to lodgers, and the AD is li. |
| Est. Annual ROI | 7-14% gross annual return |
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Recent Law Changes
What's Changed Recently
- Re-verified Sept 20, 2026 against the Arlington County Zoning Ordinance as codified June 13, 2026 (§12.9.2, §3.2.6, §14.3, §12.9.12), the county's Accessory Dwelling Permit page and the FY2027 fee schedules: the size, height, setback, parking and owner-occupancy rules are unchanged; the old page's permit-fee range ($2,800-$4,500) and 'impact fees $1,000-$1,800' were replaced with the published FY2027 figures (AD Permit $582; no impact fee); short-term rental corrected from 'not permitted' to 'allowed as an accessory homestay'.
- No accessory-dwelling amendment has been adopted since ZOA-2019-07 (adopted May 18, 2019, effective July 1, 2019), which created the current detached-AD standards; the 2026 amendments (ZOA-2026-01 Fort Myer Heights, -02 signs, -03 EV charging, adopted June 13, 2026) do not touch §12.9.2.
- Virginia SB 531 (Acts of Assembly Ch. 895, approved April 13, 2026; effective July 1, 2027) adds Code §15.2-2292.4 requiring ADUs as a permitted accessory use in single-family districts with a $500 permit-fee cap and no family-relation or restrictive-covenant requirements - but subsection I exempts any locality that adopted an ADU ordinance before Jan 1, 2026, so Arlington's §12.9.2 rules (owner-occupancy, covenant, 750 sq ft cap) stay in force unless the County Board amends them.
- Expanded Housing Option (EHO, §10.4): the Virginia Court of Appeals reversed the Circuit Court's 2024 ruling on Sept 5, 2025 and EHO permits reopened Oct 1, 2025; on May 19, 2026 the Virginia Supreme Court agreed to hear a narrow appeal about a developer's participation and did not halt EHO. EHO is a separate permit ($916) for duplexes through six-plexes and does not change the accessory-dwelling rules; §12.9.2 was never part of the lawsuit.
- FY2027 Planning and Zoning and ISD fee schedules took effect July 1, 2026: AD Permit $582, DES parking survey $387, AD certificate of occupancy $520, residential building permit $1.70 per sq ft new construction, plus a 10% automation surcharge on all fees.
Tips for Building an ADU in Arlington
- Check your zoning district first (Real Estate Assessments database or the county's interactive zoning map): only R-20, R-10, R-8, R-6, R-5, R-10T, R-15-30T and R2-7 lots with a one-family detached house qualify, and a lot with a family/caregiver suite cannot add an AD.
- Size worked example: a 1,600 sq ft house allows an AD of up to 750 sq ft (35% of 2,350 combined = 822, so the 750 cap governs); a 900 sq ft house allows only 500 sq ft or 45% of the combined area. A basement AD has no cap, which is why most Arlington ADs are basement units.
- A new backyard AD building in R-5 or R-6 is limited to a 560 sq ft footprint (650 sq ft in R-8, R-10, R-20 and the townhouse districts), 1.5 stories/25 ft, 5 ft from side and rear lines (10 ft to the eave at the rear on corner lots), 25 ft from the street and 8 ft from the house. A garage or shed built before May 18, 2019 can be converted with interior-only work and keeps its existing height and setbacks.
- Book a free pre-submission meeting with the Zoning Division (zoningadmin@arlingtonva.us, 703-228-3883) before drawing plans; staff walk through eligibility, the building-code items ISD will check (egress, fire separation, ceiling height) and stormwater and tree rules.
- Sequence: file the AD Permit in Permit Arlington at least two weeks before the building permit; after the Zoning Administrator signs, record the Declaration of Covenants at the Circuit Court land records (1425 N. Courthouse Rd) and send the receipt to Zoning - ISD will not issue the building permit without it.
- Parking rarely blocks an Arlington AD: if you already have a driveway space you keep it and add nothing; only lots with zero off-street parking may have to add one space, and even then a $387 DES survey showing the block under 65% parked waives it.
- Owner-occupancy is enforced: you or a later buyer must live in the house or the AD, an Affidavit of Compliance is re-filed on any sale or structural change, and the Zoning Administrator may inspect annually. Renting both units to two separate households from off-site is not allowed.
- Rents: HUD's FY2027 Small Area Fair Market Rents (effective Oct 1, 2026) for Arlington ZIPs run from $2,090 (22205) to $3,310 (22201/22202) for a 1-bedroom and $2,310 to $3,660 for a 2-bedroom; single-family neighborhoods (22205, 22207, 22213) sit at the lower-middle of that range.
- Cost basis: 2026 Northern Virginia guides put a detached new-build AD at $150,000-$350,000 and $200-$375 per sq ft (Excell Homes, June 2026; Renewal Homes DMV, June 2026), with Arlington-specific 2025 permit data at $200,000-$275,000 detached, $120,000-$175,000 basement and $110,000-$160,000 garage (Four Seasons Home Improvement, June 2026). Soft costs (plans, engineering, permits, survey) add $8,000-$15,000 and utility/site work $10,000-$25,000.
- Cost basis (2026-09-20 re-verification): short term allowed: Allowed only as an 'accessory homestay' with a separate one-year permit ($113 zoning fee): the host must live on the property at least 185 days a year, may rent the main house, the AD or both to lodgers, and the AD is limited to three lodgers (§12.9.2.C.8, §12.9.12). A non-resident owner cannot short-term-rent the AD.
ADU Builders in Arlington
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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.
- Arlington County Zoning Ordinance (ACZO), effective June 13, 2026 — §12.9.2 Accessory dwellings, §3.2.6 Placement, §14.3 Parking, §12.9.12 Accessory homestay, §10.4 EHO Municipal Code — Accessed 2026-09-20
- Accessory Dwelling Permit — Arlington County VA (eligibility, owner-occupancy, design, size and parking requirements; review process) Planning Department — Accessed 2026-09-20
- Zoning Ordinance Amendments (2026) and Amendments from 2003 to 2025 — ZOA-2019-07 Detached Accessory Dwellings, ZOA-2017-05, ZOA-2023-02 Planning Department — Accessed 2026-09-20
- Virginia SB 531 (2026) — Acts of Assembly Chapter 895, Code §15.2-2292.4 (chaptered as 2292.3, codified as 2292.4), effective July 1, 2027 state_statute — Accessed 2026-09-20
- EHO Trial and Appeal Information — Arlington County Attorney's Office (May 20, 2026 update) Planning Department — Accessed 2026-09-20
- FY27 Planning and Zoning Fee Schedule (effective July 1, 2026) — Zoning fees p. 6, building permits reviewed by zoning p. 8, certificates of occupancy p. 9 fee_schedule — Accessed 2026-09-20
- FY27 Inspection Services Division (ISD) Fee Schedule (effective July 1, 2026) — building, electrical, mechanical and plumbing permit fees fee_schedule — Accessed 2026-09-20
- Permit Arlington Center Fee Schedules Planning Department — Accessed 2026-09-20
- Excell Homes — How Much Does an ADU Cost in Northern Virginia? (2026) industry — Accessed 2026-09-20
- Four Seasons Home Improvement — Arlington's ADU Expansion: Permit Trends, Costs & Homeowner Opportunities 2026 industry — Accessed 2026-09-20
- Renewal Homes DMV — Accessory Dwelling Units in Virginia: 2026 Guide industry — Accessed 2026-09-20
- DC Structures — Virginia ADUs: Floor Plans & Builders (prefab kits, Jan 2026) industry — Accessed 2026-09-20
- HUD FY2027 Small Area Fair Market Rents — Washington-Arlington-Alexandria, DC-VA-MD HUD Metro FMR Area, Arlington ZIP codes Government Data — Accessed 2026-09-20
- HUD FY2027 Fair Market Rents — Washington-Arlington-Alexandria, DC-VA-MD HMFA Government Data — Accessed 2026-09-20
Frequently Asked Questions
Can I build an ADU in Arlington?
Yes. ADUs are allowed in R-20, R-10, R-8, R-6, R-5, R-10T, R-15-30T and R2-7 districts, on a lot with a one-family detached dwelling (§12.9.2; county AD Permit page). ADs may also be within or attached to semidetached/townhouse dwellings built under the Expanded Housing Option, §10.4. Not allowed on a lot that already has a family/caregiver suite (§12.9.2.A.1(a)). ADs are allowed by permit of the Zoning Administrator; no County Board hearing. in Arlington. The maximum size for a detached ADU is Gross floor area capped at the lesser of 750 sq ft or 35% of the combined floor area of house plus AD when the house is at least 1,000 sq ft; 500 sq ft or 45% when the house is under 1,000 sq ft (§12.9.2.A.2(e)). A detached accessory building approved after May 18, 2019 may hold an AD only if its footprint is 560 sq ft or less in R-5/R-6, 650 sq ft or less in the other R districts (§12.9.2.A.2(d)). GFA counts attic and basement space (§3.1.1).. Owner-occupancy is required: Required: the owner of the main dwelling must occupy either the main dwelling or the AD as their primary residence; otherwise the whole property may be occupied by only one family (§12.9.2.C.3). A covenant is recorded before the building permit; an affidavit of compliance is filed before the certificate of occupancy and again on any structural change or sale (§12.9.2.C.1, C.4). SB 531 (2026) does not change this: Code §15.2-2292.4(I) exempts localities whose ADU ordinance predates Jan 1, 2026.
How much does an ADU cost in Arlington?
ADU construction in Arlington typically costs $150,000-$350,000. Garage conversions run $80,000-$160,000, and prefab ADUs cost $150,000-$300,000.
How much can I rent an ADU for in Arlington?
Average ADU rents in Arlington are $2,100-$3,300/mo for a 1-bedroom and $2,300-$3,700/mo for a 2-bedroom unit.
Do I need parking for an ADU in Arlington?
No new space is required if the lot already has one or more off-street spaces - existing spaces must be kept (1 or 2 kept; at least 2 kept if more exist). A lot with no off-street parking must add one space unless a County parking survey finds the block less than 65% parked (§14.3 table; $387 DES parking-survey fee, FY2027).. Check with Arlington 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 Arlington?
The permit review timeline in Arlington is About 30 days for the AD Permit once the Zoning Division accepts the application as complete (county AD Permit page); the county recommends filing it at least two weeks before the building-permit application. No published review time for the residential building permit.. Permit fees: AD Permit $582 plus $387 if a DES parking survey is needed (FY2027 Planning and Zoning fee schedule, effective July 1, 2026). Building permit $1.70 per sq ft for new construction/additions or $0.63 per sq ft for alterations, plus a 2% state levy and a 10% automation surcharge; CO for an AD $520.
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