San José ADU setbacks: cottage or garage conversion?

For a new detached cottage

The City checklist separates City standards from State standards. For a new detached ADU, its State-standard column lists 4 ft side and rear setbacks. HCD explains that required side and rear setbacks generally cannot exceed 4 ft under Government Code section 66314(d)(7).

This is not a promise that every spot in your backyard is buildable. Front setbacks, height, access, easements and site conditions need separate review. Measure from the legal property line, rather than assuming the fence marks it.

Do not combine the most favorable entries from the City and State columns. San José says the two sets of standards cannot be mixed. Ask the City which complete set applies to your proposed design.

Source: San José ADU Universal Checklist, Part 3 and footnotes (PDF). Last verified: 2026-10-09.

Source: California HCD ADU Handbook, March 2026, “Setbacks” (PDF). Last verified: 2026-10-09.

For an existing garage conversion

A garage close to the rear boundary is not automatically ruled out. HCD describes a no-setback rule for conversions within existing living areas or accessory structures. It also covers replacement structures in the same location and dimensions.

That does not mean an enlarged or relocated garage gets the same exception. Show the City the existing footprint and the proposed changes before relying on it. Existing-structure conversions still need applicable building, health, safety and fire compliance.

San José’s checklist footnote allows zero setbacks for qualifying conversions, subject to Building and Fire requirements. A zoning exception does not settle whether your walls, openings or access meet those requirements.

Source: California HCD ADU Handbook, “Setbacks” and “66323 Units” (PDF). Last verified: 2026-10-09.

Source: San José ADU Universal Checklist, Part 3, footnote 2 (PDF). Last verified: 2026-10-09.

A setback is not the same as fire access

Space beside a building can serve several purposes, and passing one check does not pass them all. The City FAQ describes a minimum 4 ft clear access path for fire access. It also describes access-distance and hydrant-proximity tests.

Failing those fire-access tests may require a Fire Variance and additional safety measures. Confirm the path, gates and obstructions with the City before treating a setback measurement as your answer.

Source: San José ADU FAQs, fire access. Last verified: 2026-10-09.

What to check on your own lot

Start with a site plan showing property lines, existing buildings and your proposed ADU footprint. For a conversion, mark which walls stay and whether the footprint changes. Then check easements and any site restrictions.

San José’s checklist flags flood zones, geological hazards, historic status and wildland-urban interface requirements. Easements often prohibit building within their area. These checks can change your design even when the side and rear setbacks appear sufficient.

Source: San José ADU Universal Checklist, property checks (PDF). Last verified: 2026-10-09.