Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Henderson ADU cost →Building an ADU in Henderson costs between $110,000-$260,000 for new construction, with per-square-foot costs averaging $180-$330. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $50,000-$120,000, while prefab/modular ADUs fall in between at $80,000-$180,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | No ADU line in the DSC fee schedule (eff. 10/1/2025). Closest rows: Accessory Building - Residential at 1,000 sq ft = $1,303 plan check + $1,266 inspection (MPE included); Single-Family Addition at 1,000 sq ft = $1,601 + $1,555. Confirm the fee category at intake. |
| Impact Fees | Not published for ADUs. Henderson has a Residential Construction Tax chapter (HMC 19.17); whether it and any utility connection charges are assessed on an ADU is determined at intake. Confirm with the Development Services Center. |
| 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 Henderson, where we have them — free, no obligation.
Get Henderson builder quotes →Permit fees in Henderson are No ADU line in the DSC fee schedule (eff. 10/1/2025). Closest rows: Accessory Building - Residential at 1,000 sq ft = $1,303 plan check + $1,266 inspection (MPE included); Single-Family Addition at 1,000 sq ft = $1,601 + $1,555. Confirm the fee category at intake.. The review timeline is Not published for residential permits. The DSC offers over-the-counter review for qualifying permits and an expedited-review option; ask at intake for the current turnaround., with plan check: Plan check is priced with inspection in DSC Table A (eff. 10/1/2025) and includes mechanical, plumbing and electrical review: $1,079 at 200 sq ft, $1,164 at 600 sq ft, $1,303 at 1,000 sq ft for a residential accessory building. Planning-side fees, if needed: Design Review $274, Administrative Adjustment $164, Zoning Verification Letter $109 (eff. 8/1/2025).. Impact fees are Not published for ADUs. Henderson has a Residential Construction Tax chapter (HMC 19.17); whether it and any utility connection charges are assessed on an ADU is determined at intake. Confirm with the Development Services Center.. Pre-approved plans: No city pre-approved ADU plan program identified as of September 2026 (none on the Community Development checklists and handouts page).
| 1-Bedroom Rent | $1,350-$1,900/month |
| 2-Bedroom Rent | $1,600-$2,250/month |
| Annual Rental Income (est.) | $19,500/year |
| Payback Period (est.) | 9.5 years |
| Short-Term Rental | Not addressed in the ADU standards. Rentals under 30 days are a separate use (“S” in RS/RM/RH) governed by Sec. |
| Overall ROI Estimate | 5-7% return on cost |
A typical ADU in Henderson generates approximately $19,500 per year in rental income based on average 1-bedroom rents. At an average construction cost of $185,000, the estimated payback period is 9.5 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Henderson 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 Henderson: $50,000-$120,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $80,000-$180,000.
3. Pre-approved plans — Henderson 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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