ADU Pass
Modesto
Stanislaus County portion
Also in: No County
ADU Pass helps homeowners in Modesto, Stanislaus County, California navigate the permit paperwork for building an accessory dwelling unit. This area covers 7 ZIP codes.
Map
ADU details
ADU legality: allowed
Modesto operates an ADU Express same-day plan-check appointment program (one-hour slot, immediate feedback, possible same-day approval for compliant projects).
Cost scenarios
| Scenario | Sq ft | Permit | Build | Total |
|---|---|---|---|---|
| minimum | 150 | $1,200 | $41,250 | $42,450 |
| 600 | 600 | $2,200 | $165,000 | $167,200 |
| midpoint | 675 | $2,200 | $185,625 | $187,825 |
| 1000 | 1,000 | $4,500 | $275,000 | $279,500 |
| maximum | 1,200 | $6,000 | $330,000 | $336,000 |
Fee breakdown (as of 2026-04)
Permitting process
Viability (permitted uses)
- Long-term rental: yes Long-term rental (30+ days) explicitly permitted; AB 976 permanently removed owner-occupancy requirement effective 2024-01-01.
- Short-term rental: no California Government Code §65852.2(a)(6) prohibits cities from approving STR (under 30 days) use of ADUs; Modesto enforces.
- Office rental: with-restrictions Detached commercial office rental to outside tenants is not a permitted ADU use; ADUs are residential. Home occupation by the property owner is allowed.
- Home office: yes Home occupation permitted under MMC zoning with restrictions on signage, employees, and customer traffic.
- Studio / workshop: yes Personal artist/maker studio is a permitted accessory use of an ADU.
- Agriculture: with-restrictions Modesto's Central Valley agricultural identity (orchards, dairy, almonds) means more permissive small-livestock and agricultural-accessory standards than coastal CA cities; check current MMC district standards.
- Relative support: yes Family-occupancy ADU explicitly permitted; no relationship requirement under California state law.
Incentives
Contacts
Utilities
- Water: Modesto Irrigation District (MID) — water and electric serving most of Modesto; some areas under the City of Modesto Public Works domestic water system · 30d connect · $4,500
MID is a publicly-owned irrigation/utility district serving Modesto and surrounding Stanislaus County agriculture; provides treated domestic water and retail electric service. ADUs typically share the primary residence's meter unless separately metered. - Sewer: City of Modesto Public Works — Wastewater Division · 30d connect · $5,000
City operates the Sutter Avenue and Jennings Road treatment facilities. Sewer-lateral capacity check required for new ADU connection. - Electric: Modesto Irrigation District (MID) · 21d connect · $1,200
MID retail electric service; rates substantially below PG&E coastal rates. Service-upgrade lead times shorter than PG&E territories. - Gas: Pacific Gas & Electric (PG&E) · 21d connect · $1,200
Despite MID's electric monopoly, gas service in Modesto is from PG&E. Title 24 2025 incentivizes all-electric ADU designs to skip gas connection.
Property values & taxes
Construction timeline
Realistic total: best 7mo · typical 11mo · worst 16mo
Central Valley contractor lead times shorter than Bay Area; MID electric service-upgrade lead times shorter than PG&E territories.
Modular pathway inspectors are occasional with modular
Financing
State ADU loans:
- CalHFA ADU Grant Program up to $40,000
- HCD ADU Funding index
Insurance impact
HOA prevalence & preemption
Modesto's HOA prevalence concentrated in newer master-planned subdivisions (Village One, Bystrum, Salida). California's AB 670 / AB 3182 Davis-Stirling preemption voids any HOA covenant prohibiting ADUs on single-family lots; residual HOA design-standards authority remains.
Regulatory overlays (2)
- flood-zone
Tuolumne River and Stanislaus River corridors create FEMA SFHA exposure in parts of Modesto (south and east of downtown). Properties in Zone AE require flood-elevation certificates. - seismic-retrofit-zone
Calaveras Fault system within 50-70 miles; ASCE 7-22 Seismic Design Category D applies. Standard CRC seismic detailing required.
Technical envelope (climate & building code)
Climate & energy code
Building code
Amendments:
- Amendment
- Amendment
Contractor market (aggregate)
Legal history (timeline)
Current ordinance: Modesto Municipal Code §10-4.115 — Accessory Dwelling Units (Table 4.1-3), adopted 2017-03-14, last amended 2024-06-01
- 2017-03-14 — Modesto initial ADU ordinance (post-AB 2299/SB 1069) (city-ordinance)
First Modesto ADU ordinance update aligning local code to 2016 California ADU reforms.
Effect: Established by-right ADU permitting in residential zones, eliminated owner-occupancy requirements, and codified initial Modesto-specific size and setback standards in MMC Title 10. - 2020-09-22 — Modesto ADU code refresh — MMC §10-4.115 update (city-ordinance)
Local conforming amendments to align with AB 68 / AB 881 / SB 13 (2020 statewide overhaul).
Effect: Codified by-right ministerial ADU track, prohibited impact fees on ADUs <750 sqft, and clarified zoning standards in MMC Table 4.1-3. - 2023-11-27 — HCD review letter — Modesto ADU ordinance compliance findings (city-ordinance)
California HCD reviewed Modesto's ADU ordinance and issued findings.
Effect: Identified specific provisions HCD flagged as inconsistent with state law, prompting Modesto to address those items in subsequent code amendments. - 2024-06-01 — ADU Express program launched (city-ordinance)
Modesto introduced the ADU Express same-day appointment program for ministerial ADU review.
Effect: One-hour scheduled appointments at Permit Counter where city staff review submitted ADU/JADU plans, provide immediate feedback, identify required corrections; compliant plans may receive same-day approval — substantially shorter than traditional plan-check cycles.
Known issues (1)
- other — Properties in FEMA SFHA along the Tuolumne and Stanislaus river corridors require flood-elevation certificates for ADU permits; raised foundations may add $15,000-$40,000 to project cost.
Stanislaus County — county ADU rules and overlays
County ADU ordinance
California state — ADU law and programs
State ADU law
California has the most aggressive statewide ADU preemption regime in the US, built from ~15 bills passed 2019-2025 and enforced by the Department of Housing and Community Development (HCD). The 2026 HCD ADU Handbook addendum (in effect with the 2025 Title 24 code cycle) is the operative state-level reference. The regime does four things at once: (1) preempts local zoning that would ban or unreasonably restrict ADUs; (2) imposes by-right ministerial approval with short statutory deadlines; (3) caps fees and utility-connection charges; and (4) empowers HCD to void non-compliant local ordinances.
State HOA preemption
California has the strongest statewide HOA-preemption regime in the US for accessory dwelling units, built from two bills: AB 670 (2019) voided ADU-prohibiting covenants on single-family residential lots, and AB 3182 (2020) extended and codified the preemption into the Davis-Stirling Common Interest Development Act (Civil Code §§ 4740 / 4741). The combination prohibits common-interest communities from banning ADUs, restricting rentals below 25% of separate interests, or treating ADUs as separate HOA interests. Limits remain: HOAs retain authority over reasonable design standards and statutory height limits, and the 2026 Carlsbad case (CalMatters coverage) established that an HOA's documented design-standards regime can effectively delay or constrain ADU approval short of outright prohibition.
State financing programs
California's flagship state-level ADU financing program — the CalHFA ADU Grant Program — is paused and has not been refunded since the original $100 million allocation was fully deployed 2023-12-28. The program provided up to $40,000 per qualifying homeowner for pre-construction and non-recurring closing costs and financed approximately 2,500 ADUs in two rounds. As of 2026-04, no new funding round has been announced in the state budget. CalHFA continues to publish anti-scam warnings because bad actors actively solicit homeowners claiming access to grant funds that no longer exist. State-level financing activity has shifted to local pilot programs (San Francisco, San Jose, Los Angeles, San Diego) and private financing products (Fannie Mae ADU mortgage, HELOC, construction-to-permanent).
State housing programs
California's state-level ADU programs are concentrated at HCD (technical guidance, ordinance review, enforcement) and the paused CalHFA grant pipeline (covered under stateFinancing). The state does not operate a central pre-approved ADU plan library — instead, AB 1332 (2024) created a preemption framework for local pre-approved plans with a 30-day ministerial-approval deadline, and major cities (Los Angeles, San Diego, San Jose, Sacramento, Berkeley) have rolled out their own plan catalogs. The California YIMBY coalition and other housing-policy organizations play an influential role in bill drafting; they are not state agencies but effectively drive much of the ADU legislative agenda. The Title 24 code cycle (now 2025, in effect for 2026 permits) is the authoritative building-code baseline.
Federal (United States) — ADU-relevant rules and programs
Federal ADU law
The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.
Federal financing programs
Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.
Federal tax credits
There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.
Federal housing programs
HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.