We found no dated, Stockton-only survey as of November 2026. Block Renovation's June 2026 guide for Sacramento, the nearest large market, lists the ranges below. Stockton labor and land costs can differ, so treat them as a benchmark.
Published ranges
| ADU type | Published range |
|---|---|
| Junior ADU | About $50,000 to $100,000 |
| Garage conversion | About $80,000 to $150,000 |
| Attached ADU | About $100,000 to $300,000 |
| Detached ADU | About $150,000 to $300,000 or more |
These are published ranges, not a quote for your lot.
What moves the number?
- Utility runs. Distance to the sewer and whether the electrical panel needs an upgrade.
- Foundation and soil. Slopes, expansive soil and tree roots.
- Size and finishes. Kitchens and bathrooms carry the most cost per square foot.
- Access. Narrow side yards slow every delivery.
- Fees. Plan check and permit fees, plus school or utility fees on larger units.
What lowers it?
- Keeping the unit at or under 750 square feet, which avoids impact fees under state law.
- A simple roofline and a plan that fits the setbacks without custom engineering.
- Converting existing space instead of building new, when the structure is sound.
Sources, checked November 2026: Block Renovation, "Sacramento ADU Costs 2026" (June 29, 2026). Published ranges for a nearby market, not a quote.
Updated November 2026