Does Modesto, CA have its own adu rules ordinance?

No. Modesto, CA does not appear to have a local adu rules ordinance, California state law applies instead. The rules summarized on this page come from CA Government Code §65852.2 — ADUs.

Key Facts Ordinance Text Full Breakdown Violations FAQ Sources More in Modesto

Modesto, CA Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

ADU rules in Modesto, CA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Code Section: Modesto MC sections 10-4.501 to 10-4.512
Max Size (Detached): 1,200 sq ft
Max Height (Detached): 16 ft (18 ft near transit)
Side/Rear Setback: 4 ft
State Law: Cal. Gov. Code section 65852.2
Adopting Ordinance: Ord. No. 3762-C.S. (eff. May 11, 2023)

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in California under recent ADU streamlining laws. The Modesto, CA rules below cover local size, height, and setback requirements.

Summary

Modesto Municipal Code Article 5 (sections 10-4.501 to 10-4.512) permits ADUs ministerially on lots with a single-family or duplex dwelling, capping detached units at 1,200 sq ft and 16 ft in height (18 ft near major transit), with 4 ft side and rear setbacks. Standards mirror Govt Code section 65852.2.

Ord. No. 3762-C.S., section 2, effective May 11, 2023, repealed section 10-4.115, which pertained to accessory dwelling units. (Current standards are codified at sections 10-4.501 through 10-4.512: minimum four (4) foot side and four (4) foot rear yard setbacks; detached ADU height limit of sixteen (16) feet, or eighteen (18) feet within one-half mile walking distance of a major transit stop.)

Source: CA Government Code §65852.2 — ADUsView official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 71).

Full Breakdown

Modesto's ADU article was adopted by Ord. No. 3762-C.S. (effective May 11, 2023), which repealed former section 10-4.115 and replaced it with sections 10-4.501 through 10-4.512. Per section 10-4.505, ADUs are allowed on lots with an existing or proposed single-family dwelling or duplex. Section 10-4.506 caps detached ADUs at 1,200 sq ft and attached ADUs at 50% of the primary dwelling or 800 sq ft, whichever is greater. Section 10-4.507 limits detached ADU height to 16 ft, or 18 ft when within one-half mile walking distance of a major transit stop, and allows attached ADUs up to 25 ft or the underlying zone limit. Detached ADUs must observe a minimum 4 ft side and rear setback. The Modesto regulations implement California Government Code section 65852.2, which preempts local ADU restrictions and requires ministerial (over-the-counter) approval within 60 days of a complete application.

Violations & Fines

An ADU built without a permit, or one that exceeds height/size limits, is subject to code enforcement under Title 1 Chapter 6, which authorizes administrative citations, stop-work orders, and recordation of a notice of violation. Unpermitted structures may have to be brought into compliance or removed at the owner's expense.

Frequently Asked Questions

Do I need a discretionary permit for an ADU in Modesto?

No. California Government Code section 65852.2 and Modesto MC section 10-4.503 require ADU applications that meet the objective standards in Article 5 to be approved ministerially (over the counter), without a hearing, within 60 days of a complete application.

How tall can my detached ADU be?

Modesto MC section 10-4.507 limits a detached ADU to 16 ft, increased to 18 ft if the lot is within one-half mile walking distance of a major transit stop. Attached ADUs may go up to 25 ft or the height limit of the underlying zone, whichever is less.

Can I build an ADU on a duplex lot?

Yes. Modesto MC section 10-4.505(a) treats R-1 lots with an existing or proposed duplex as eligible for an ADU under the single-family-dwelling rules.

Sources & Official References

Other rules in Modesto

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All Modesto rules

How Modesto compares: Easiest Cities to Build an ADU·California rules heatmap·Compare Modesto to another location·View the California accessory structures overview

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