Modesto Permit Guide · 2026

ADU / Garage Conversion Permits
in Modesto, CA

Permit fees for a ADU or garage conversion in Modesto typically run $875–$3,500. Here's exactly which permits you need, what they cost, and how long CA review takes.

Do you need a permit for a ADU or garage conversion in Modesto?

Always — converting space into a dwelling unit triggers full plan review, zoning approval, and utility sign-offs in Modesto. Permit fees for a typical $174,735 ADU or garage conversion run about $875–$3,500 (valuation-based fee plus plan review), and CA plan review typically takes 4–10 weeks.

Permits you'll likely need

Building

full plan review for the dwelling conversion

Zoning / occupancy

ADU ordinance compliance and occupancy approval

Utilities

sewer, water, and electrical service connections

Fire / egress

separate egress and smoke/CO requirements

Usually exempt

Nothing meaningful — every part of a ADU or garage conversion runs through permitting. Budget for it up front.

CA permit note

Title 24 Energy Compliance: California Any HVAC replacement, window change, or significant remodel triggers Title 24 compliance. Reddit users report surprise costs for additional insulation, cool roofs, or HVAC efficiency upgrades. Some contractors ignore this—it becomes your problem at inspection.

How to get ADU or garage conversion permits in Modesto

1
Confirm what triggers a permit
Building, Zoning / occupancy, Utilities, Fire / egress permits apply when the scope includes full plan review for the dwelling conversion. Cosmetic-only scopes may be exempt.
2
Budget the fee
Plan for $875–$3,500 in Modesto — a valuation-based fee on a typical $174,735 project plus plan review.
3
Apply with complete documents
Submit scope, drawings, and contractor license info to the Modesto building department. CA plan review typically takes 4–10 weeks.
4
Verify it in the bid
A complete Modesto bid lists permit fees as a line item. If a bid omits permits — or suggests skipping them — analyze it before signing.

ADU / Garage Conversion permits in Modesto: FAQ

Do I need a permit for a ADU or garage conversion in Modesto?

Always — converting space into a dwelling unit triggers full plan review, zoning approval, and utility sign-offs in Modesto, CA. When in doubt, call the Modesto building department before work starts — unpermitted work can block a future sale.

How much do ADU or garage conversion permits cost in Modesto?

Expect roughly $875–$3,500 in Modesto for a typical $174,735 ADU or garage conversion. Most jurisdictions charge a valuation-based fee of about 0.5–2% of project value, plus plan review and per-trade permit minimums.

How long does a ADU or garage conversion permit take in Modesto?

Simple trade permits are often issued over the counter in Modesto. Where plan review applies, CA turnaround typically runs 4–10 weeks. Submit complete drawings the first time — resubmittals are the most common cause of delay.

Who pulls the permit — me or my contractor?

Usually your contractor pulls permits for a ADU or garage conversion, and their license is attached to the work. A contractor who asks you to pull an owner's permit for contractor-performed work is shifting liability onto you — treat that as a red flag when reviewing bids.

More Modesto permit guides

ADU / Garage Conversion permits in other CA metros

Is your ADU or garage conversion bid fair?

A typical Modesto ADU or garage conversion runs $174,735. Check your contractor's bid — permits included — against live 2026 local data, free.

Modesto ADU or garage conversion costs AUDIT MY BID

Data sources: Zonda Cost vs Value 2025; Houzz 2024 Cost Guides; BLS OEWS 2023; FRED regional price indices; Reddit homeowner & contractor reports.

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ADU / Garage Conversion Permits in Modesto, CA