Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Gilbert ADU cost →Building an ADU in Gilbert costs between $150,000-$280,000 for new construction, with per-square-foot costs averaging $175-$350. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $80,000-$150,000, while prefab/modular ADUs fall in between at $150,000-$300,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | Valuation-based: a $150,000 valuation is $1,145 permit plus $744.25 plan review (65% of the permit fee), about $1,890; add a $1,000 Administrative Use Permit if over 1,000 sq ft (Development Services Fee Schedule, Res. 4563 eff. July 1, 2025, revised Sept 15, 2026). |
| Impact Fees | System Development Fees for an ADU: $2,339.50 parks and recreation + $438.50 traffic signals + $752.50 roads + $284.50 police + $361.75 fire = $4,176.75, one quarter of the single-unit rate (adopted April 16, 2024, effective July 1, 2024). Water and wastewater connection fees ($18,396-$18,603 for a 3/4-inch meter) apply only if a new or larger meter is needed; ADU utilities normally come off the house, so confirm with the One Stop Shop (480-503-6728). |
| 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 Gilbert, where we have them — free, no obligation.
Get Gilbert builder quotes →Permit fees in Gilbert are Valuation-based: a $150,000 valuation is $1,145 permit plus $744.25 plan review (65% of the permit fee), about $1,890; add a $1,000 Administrative Use Permit if over 1,000 sq ft (Development Services Fee Schedule, Res. 4563 eff. July 1, 2025, revised Sept 15, 2026).. The review timeline is Published review goals: 12 working days for the first review of a single-family plan set and 8 for the second (room additions 8/4); Express Permitting reviews eligible detached residential structures in 1-3 working days for the plan-review fee plus 60% (Project Review Time Frames, Mar 2026)., with plan check: Full construction plan review through the One Stop Shop; a soils report is required unless the subdivision has one on file or you sign the Town's soils waiver; a third or later review may be billed at $150 per hour; expedited review costs twice the plan-review fee (Fee Schedule pp. 8-9; ADU Guide).. Impact fees are System Development Fees for an ADU: $2,339.50 parks and recreation + $438.50 traffic signals + $752.50 roads + $284.50 police + $361.75 fire = $4,176.75, one quarter of the single-unit rate (adopted April 16, 2024, effective July 1, 2024). Water and wastewater connection fees ($18,396-$18,603 for a 3/4-inch meter) apply only if a new or larger meter is needed; ADU utilities normally come off the house, so confirm with the One Stop Shop (480-503-6728).. Pre-approved plans: None published on gilbertaz.gov as of Sept 20, 2026. ARS 9-461.20 (SB 1529, Laws 2025 ch. 259) requires every Arizona municipality to offer at least three pre-approved ADU design plans from July 1, 2026; ask the One Stop Shop whether Gilbert's are available..
| 1-Bedroom Rent | $1,500-$1,800/month |
| 2-Bedroom Rent | $1,850-$2,300/month |
| Annual Rental Income (est.) | $19,800/year |
| Payback Period (est.) | 10.9 years |
| Short-Term Rental | Yes, with a Town of Gilbert Short-Term Rental licence (registration through Neumo/GovOS; licence and renewal fee $250 from Oct 1, 2026), an ADOR TPT licence and written notice to adjacent neighbors (STR ordinance adopted. |
| Overall ROI Estimate | 6-11% gross rental yield |
A typical ADU in Gilbert generates approximately $19,800 per year in rental income based on average 1-bedroom rents. At an average construction cost of $215,000, the estimated payback period is 10.9 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Gilbert 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 Gilbert: $80,000-$150,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $150,000-$300,000.
3. Pre-approved plans — available in Gilbert, which can save $3,000-$10,000 in design costs and 2-3 months in review time. 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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