Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Fremont ADU cost →Building an ADU in Fremont costs between $250,000-$460,000 for new construction, with per-square-foot costs averaging $300-$480. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $100,000-$170,000, while prefab/modular ADUs fall in between at $150,000-$300,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | Limited Design Review for an ADU/JADU: $2,000 deposit billed at cost. Building plan check and inspection are valuation-based (e.g. $967.27 + $5.91 per $1,000 above $100,000) plus 15% Community Planning and 3% technology surcharges (Master Fee Schedule eff. 7/1/2026); preapproved plans $1,000 flat. |
| Impact Fees | None. The City's ADU Informational Handout (updated 1/5/2026) states ADUs are not subject to development impact fees regardless of size, and FMC 18.290.110(b) exempts ADU remodels and additions; that is broader than the state floor, which exempts only ADUs of 750 sq ft or less (Gov. Code 66311.5). Utility connection fees (ACWD water, Union Sanitary District sewer, PG&E's required separate electric meter) and Fremont Unified School District fees may still apply. |
| 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 Fremont, where we have them — free, no obligation.
Get Fremont builder quotes →Permit fees in Fremont are Limited Design Review for an ADU/JADU: $2,000 deposit billed at cost. Building plan check and inspection are valuation-based (e.g. $967.27 + $5.91 per $1,000 above $100,000) plus 15% Community Planning and 3% technology surcharges (Master Fee Schedule eff. 7/1/2026); preapproved plans $1,000 flat.. The review timeline is Completeness notice within 15 business days and a decision within 60 days of a complete application (FMC 18.190.005(b)(4)); deemed approved if the City misses the 60 days (SB 543, Jan 2026). Preapproved plans are reviewed in 7 business days, standard plans in 15., with plan check: The building plan-check fee covers up to three review cycles (FMC 15.10.090); further cycles cost $147/hr, and expedited plan check at the applicant's request adds $181/hr. Project valuation is set from the City's Exhibit 1 minimum values (RS Means, San Jose modifier), updated each July 1. A preapproved detached plan is reviewed in 7 business days for a flat $1,000; a standard plan set in 15 business days.. Impact fees are None. The City's ADU Informational Handout (updated 1/5/2026) states ADUs are not subject to development impact fees regardless of size, and FMC 18.290.110(b) exempts ADU remodels and additions; that is broader than the state floor, which exempts only ADUs of 750 sq ft or less (Gov. Code 66311.5). Utility connection fees (ACWD water, Union Sanitary District sewer, PG&E's required separate electric meter) and Fremont Unified School District fees may still apply.. Pre-approved plans: Yes, but the library is thin right now: on January 1, 2026 the 2025 California codes invalidated every plan preapproved under the 2022 cycle, and as of September 2026 one updated plan (1 bed/1 bath, 499 sq ft) is valid while nine 2022-cycle plans (496-1,000 sq ft) await resubmittal. The program covers detached ADUs only; you contract with the plan's designer and still submit site-specific plans, studies and engineering..
| 1-Bedroom Rent | $2,600-$3,000/month |
| 2-Bedroom Rent | $3,100-$3,700/month |
| Annual Rental Income (est.) | $33,600/year |
| Payback Period (est.) | 10.6 years |
| Short-Term Rental | No. An ADU or JADU may not be rented for a term of less than 30 days (FMC 18.190.005(b)(6)). |
| Overall ROI Estimate | 7-10% gross annual rent yield on a $250,000-$460,000 detached build renting at $2,600-$3,000/mo; net return is lower after vacancy, property tax and upkeep |
A typical ADU in Fremont generates approximately $33,600 per year in rental income based on average 1-bedroom rents. At an average construction cost of $355,000, the estimated payback period is 10.6 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Fremont 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 Fremont: $100,000-$170,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $150,000-$300,000.
3. Pre-approved plans — available in Fremont, 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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