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Permit guides

ADU Permits in Hercules: a Homeowner's Guide

Hercules publishes its own ADU Mini-Guide — and enforces a 30-foot front setback most cities don't have.

Last updated October 2026. Rules change; always confirm current requirements with the city before you build.

Who handles your permit

ADU permits in Hercules go through the Community Development Department (111 Civic Drive, Hercules, CA 94547, (510) 799-8200). The Planning Director approves compliant ADUs ministerially — no public hearing, no extra permits beyond the building permit — and must act within 60 days of a complete application. Start with the city's ADU Mini-Guide for Homeowners.

What you can build

Hercules' local numbers (tighter than state minimums in places):

Hercules uses the 'Statewide Exempt (66323) Unit' concept: conversions, new detached ADUs up to 800 sq ft with 4-ft setbacks at 16 ft height, and JADUs. JADUs may expand up to 150 sq ft beyond the existing structure for an entrance.

Watch the front setback

The number that surprises people in Hercules: 30 feet from the front property line (20 feet from a street-facing side line) for ADUs needing an ADU permit. That's far more restrictive than the 4-foot side/rear standard and rules out front-yard placement entirely.

Size caps also sit below the state maximum: 850 square feet for studios and one-bedrooms, 1,000 for two-plus bedrooms. And short-term rentals under 30 days are prohibited for both ADUs and JADUs.

What goes into the submittal

Hercules' submittal basics:

• Building permit application (the only permit required for compliant ADUs)
• Site plan, floor plans, elevations (existing and proposed)
• Structural calculations and Title 24 energy compliance
• Digital PDF plan set per the city's submittal standards
• Electrical, plumbing, and mechanical layouts

Where applications usually get stuck

• 30-foot front setback. The strictest common setback in the East Bay batch.
• 850/1,000 size caps. Below the 1,200 state max — design to Hercules' numbers, not the state's.
• No short-term rentals. Under-30-day rentals are prohibited outright.
• Hillside lots. Parts of Hercules slope toward the bay — expect grading and drainage review.