ADU feasibility · Modesto, CA

ADU feasibility in Modesto: rules, costs & what you can build (2026)

Q: How big an ADU can I build in Modesto?

Modesto allows a detached ADU up to 1,200 sq ft. Your actual buildable size is the smaller of that cap and what the lot allows after the 4 ft setbacks and your existing home's footprint.

Q: Do I need to live on the property to rent an ADU in Modesto?

No. California permanently removed the owner-occupancy requirement for standard ADUs, so you can rent both the main home and the ADU. Junior ADUs that share sanitation with the main house are the exception.

Updated July 2026 · Rules current as of the 2026 California ADU framework

Modesto follows California's statewide ADU framework — no owner-occupancy requirement and parking waived near transit. Here are the 2026 rules that decide what you can build, typical costs and rents, and how to check the numbers for your specific lot.

Modesto ADU rules at a glance (2026)

Max detached ADU: 1,200 sq ft
Side / rear setback: 4 ft
Owner-occupancy: Not required
Parking: Waived near transit
Approval: Ministerial · 60-day
Impact fees: Waived under 750 sq ft

These reflect California's statewide ADU framework, which Modesto must follow. Cities can apply objective standards on height, design, and landscaping, but cannot cap a detached ADU below the state minimums or add discretionary review.

What the rules mean for feasibility

The legal ceiling is 1,200 sq ft under California's statewide framework. Your buildable size is whatever the lot allows after the 4 ft setbacks and your existing home's footprint — so a tight lot often pencils smaller than the cap. With a 16 ft height limit and impact fees waived under 750 sq ft, a one-bedroom in the 600–800 sq ft range is frequently the sweet spot for return.

Cost & rent snapshot

Build cost

$120k–$290k

Rent · 1BR

$1,300–$1,900

Rent · 2BR

$1,600–$2,400

Typical 2026 ranges for detached new construction (garage conversions run lower, ~$65k–$150k). Actual figures depend on your lot, finish level, and neighborhood comps — run your address below for site-specific numbers.

Local tip: The city's ADU Express offers same-day plan review; a second story over a garage can trigger administrative review.

See what your Modesto lot can actually build.

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Frequently asked questions

How big an ADU can I build in Modesto?

Up to 1,200 sq ft for a detached ADU. Your real buildable size is the smaller of that and what fits after the 4 ft setbacks and your home's existing footprint.

Do I have to live on the property to rent it out?

No. California permanently removed owner-occupancy for standard ADUs, so you can rent both the main home and the ADU. JADUs sharing sanitation with the main house are the exception.

Is parking required?

Usually no — California waives ADU parking within a half-mile of transit and for garage conversions. When required, the max is one space per unit.

How long does approval take?

ADU permits are ministerial (no public hearing). The city has a 60-day shot clock to approve or deny a complete application.

Sources: City of Modesto; California HCD ADU Handbook (2026); Gov. Code §§66314–66323; California HCD ADU Handbook (2026 update). Rules summarized for general guidance and current as of July 2026 — ADU law changes frequently and your lot's specifics govern. Verify with the Modesto planning or building department before designing or contracting.