Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Arlington ADU cost →Building an ADU in Arlington costs between $150,000-$350,000 for new construction, with per-square-foot costs averaging $200-$400. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $80,000-$160,000, while prefab/modular ADUs fall in between at $150,000-$300,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & 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. |
| Site Prep & Foundation | $10,000 – $35,000 |
| Framing & Structure | $15,000 – $45,000 |
| Plumbing | $8,000 – $20,000 |
| Electrical | $5,000 – $15,000 |
| HVAC | $3,000 – $8,000 |
| Interior Finishes | $15,000 – $40,000 |
Quotes for the same ADU commonly vary 20–40% between builders. We pass your request to up to 5 local builders serving Arlington, where we have them — free, no obligation.
Get Arlington builder quotes →Permit fees in Arlington are 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.. The review timeline 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., with 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.. Impact fees are 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.. Pre-approved plans: Not available.
| 1-Bedroom Rent | $2,100-$3,300/month |
| 2-Bedroom Rent | $2,300-$3,700/month |
| Annual Rental Income (est.) | $32,400/year |
| Payback Period (est.) | 7.7 years |
| 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. |
| Overall ROI Estimate | 7-14% gross annual return |
A typical ADU in Arlington generates approximately $32,400 per year in rental income based on average 1-bedroom rents. At an average construction cost of $250,000, the estimated payback period is 7.7 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Arlington and varies by market (often less than build cost).
1. Garage conversions save 40-60% vs new construction since the shell already exists. Average cost in Arlington: $80,000-$160,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $150,000-$300,000.
3. Pre-approved plans — Arlington does not offer a pre-approved/standard ADU plan program yet, so budget for custom architectural plans (typically $3,000-$15,000). See which cities offer pre-approved ADU plans.
4. State grants — California's CalHFA ADU grant (up to $40K) is currently paused; check calhfa.ca.gov/adu for status and your state for active programs.
5. Get multiple bids — ADU contractor pricing varies 20-40% for the same project. We recommend getting at least 3 quotes.
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