An ADU builder in Arlington is a licensed contractor who designs and constructs accessory dwelling units — detached backyard units, garage conversions, attached additions, and junior ADUs (JADUs). Because an ADU is a complete second dwelling, the builder coordinates foundation, framing, plumbing, electrical, and HVAC work and pulls it through Arlington's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in Virginia.
What ADU Builders Cost in Arlington [9][10][11][12]
Based on our Arlington cost data, expect the following ranges from local ADU builders. Quotes for the same scope typically vary 20-40% between contractors, so getting at least three bids is the single best way to control cost.
| New Detached ADU (all-in) | $150,000-$350,000 |
| Cost per Sq Ft | $200-$400 |
| Garage Conversion | $80,000-$160,000 |
| Prefab / Modular ADU (installed) | $150,000-$300,000 |
| City Permit & Plan Review | 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. |
For a full line-item breakdown, see our Arlington ADU cost guide. To confirm what you're allowed to build before you hire, review the Arlington ADU rules (max detached size: 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: 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.).
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How to Vet an ADU Builder in Arlington
- License: Confirm a current contractor's license in Virginia and that it's in good standing. Ask for the license number and verify it with the state board.
- ADU-specific experience: Ask how many ADUs they've completed in or near Arlington and request addresses or photos. ADU permitting and setbacks differ from a kitchen remodel.
- Portfolio & references: Get references from recent ADU clients and, if possible, visit a finished unit.
- Insurance: Verify general liability and workers' compensation coverage. Ask for a certificate of insurance.
- Written, detailed bid: Insist on an itemized, fixed-price or clearly-scoped bid — not a verbal estimate. It should state whether permits (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.), 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.), and 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.) are included.
- Permit handling: Confirm they manage Arlington's permit 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.", typically 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.) and who is responsible if revisions are required.
- Payment schedule: Avoid large upfront payments. A reasonable schedule ties payments to completed milestones.
Questions to Ask Before You Hire
- How many ADUs have you built in Arlington in the last two years?
- Is your bid fixed-price, and what would trigger a change order?
- Are permits, plan check, and utility connection fees included?
- What's a realistic timeline, including permit review (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.) and construction?
- Who is my point of contact and how are delays communicated?
- What warranty do you provide on workmanship?
- Can you share three recent Virginia ADU client references?
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