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Permit guides
ADU Permits in Modesto: a Homeowner's Guide
Modesto homeowners get access to free pre-drawn ADU designs through a county partnership — but the electric utility and flood zones deserve early attention.
Last updated October 2026. Rules change; always confirm current requirements with the city before you build.
Who handles your permit
The City of Modesto Building Safety Division issues ADU permits from 1010 10th Street, 3rd floor, Modesto. Submittals and attachments are tracked through the city's eTRAKiT system. Note: the building permit application asks for a City of Modesto business license number — if you're hiring a contractor, confirm they carry one.
What you can build
7 free plansStanislaus County pre-drawn ADU designs, 260–1,192 sq ft, usable in Modesto
eTRAKiTElectronic permit tracking and attachment system
1,200 sq ftDetached ADU max under state law
Biz licenseContractors need a City of Modesto business license
MIDModesto Irrigation District — electric and water service
60 daysState-required decision on a complete application
Seven free plans, courtesy of Stanislaus County
Stanislaus County partnered with Modesto, Ceres, Oakdale, Riverbank, Turlock, and Waterford to develop a library of pre-drawn ADU plans for detached new construction — from a 260 sq ft studio up to a 1,192 sq ft 3-bedroom — each with multiple exterior finish options. They are free to property owners in the partner cities.
Because the structural design is already reviewed, your submittal focuses on the site: placement, setbacks, foundation conditions, and utility connections. You still need a plot plan drawn to scale — the county's ADU page hosts sample site plans — and fire-sprinkler plans if the main dwelling is sprinklered.
What goes into the submittal
- Building permit application (City of Modesto form) with owner, contractor, license, and business-license details.
- Plot plan drawn to scale: parcel dimensions, structure locations, driveways, easements, setbacks from property lines and between structures.
- Floor plans and foundation details — streamlined when using the pre-drawn plans; full sets needed for custom designs.
- Title 24 energy compliance, MEP layouts, and truss calcs where applicable.
- MID coordination for electric service and meter sizing — start this in parallel, not after plan check.
Where applications usually get stuck
- MID service upgrades. Electric service and panel capacity are the most common slowdown — get MID's requirements before you finalize the electrical plan.
- Tuolumne River floodplain. Parts of Modesto sit in flood zones; elevation certificates and finished-floor heights add cost and review time.
- Contractor licensing paperwork. Missing or expired city business licenses stall issuance at the finish line.
- Setback and fire separation on tight lots. Older neighborhoods with narrow side yards trigger rated-wall requirements.
- Unpermitted prior additions. Reviewers compare plans against the assessor's record — unpermitted work on the main house gets flagged.
Not sure where to start? That's the part we do. We look at your property, map the requirements, coordinate the plans and specialists, and manage the submittal and corrections — one point of contact.