ADU Setback Requirements in California (2026)

A new ADU in California needs no more than 4 ft of setback from the side and rear property lines, and a city's front setback cannot be used to block an ADU of up to 800 sq ft. If you convert an existing legal structure, such as a garage, you need no extra setback at all. Cities can apply larger setbacks only to ADUs above what state law guarantees, and some do.

Key takeaways

• ›Side and rear setbacks for new ADUs are capped at 4 ft (Gov. Code §66314(d)(7)).
• ›Front setbacks cannot prevent an 800 sq ft ADU (AB 2221, 2022).
• ›Converting a legally built garage or accessory structure needs no additional setback.
• ›Some cities apply stricter setbacks to units larger than 800 sq ft or taller than 16 ft, so check your city page.

What is the minimum ADU setback in California?

For a new detached or attached ADU, cities can require no more than 4 ft from the side and rear property lines. That cap has been state law since AB 68 took effect in 2020. Before then, some cities required 10 ft or more.

Most cities in our data simply adopt the state number. Sacramento, Fresno, San Jose, and Los Angeles all use 4 ft side and rear setbacks for new ADUs.

Can a city enforce its front setback on an ADU?

Only up to a point. Cities can apply their normal front setback, usually the same as the main house, but AB 2221 (2022) made clear that a front setback cannot block an 800 sq ft ADU. If the only buildable spot on your lot is in the front setback area, the city has to allow an ADU of up to 800 sq ft there, with 4 ft side and rear setbacks.

This matters on shallow and corner lots. Front setbacks in our data vary, for example "typically 20–25 ft" in Thousand Oaks.

Do garage conversions need setbacks?

No. Converting an existing, legally built structure (a garage, workshop, or accessory building) to an ADU needs no additional setback. A permitted garage 2 ft from the property line can become an ADU even though a new building could not go there.

Some cities extend this to same-footprint rebuilds. In our data, Pasadena requires no side setback, and Ontario no rear setback, for conversions or same-footprint rebuilds, and Oakland allows 0 ft rear setbacks for conversions of existing structures.

The key word is "legally." If the structure was built without permits, or crosses onto a neighbor's lot, the rules differ. See how to legalize an unpermitted ADU for the AB 2533 path for pre-2020 units.

When can a city require more than 4 ft?

State law guarantees an 800 sq ft ADU, at least 16 ft tall, with 4 ft side and rear setbacks. Above that, some cities apply the zone's normal setbacks:

• ›Escondido: 4 ft for ADUs up to 800 sq ft; underlying zone setbacks for ADUs of 800 to 1,200 sq ft.
• ›Riverside: 4 ft for one-story ADUs; ADUs over 16 ft must meet the main home's setbacks.
• ›San Francisco: 4 ft for detached ADUs under the State program; Local program ADUs follow zoning district rear yard rules.

Separation from the main house can also matter, for example 6 ft in Temecula.

Worked example: an 800 vs. 1,000 sq ft ADU in Escondido

Take a 60 ft wide Escondido lot and assume the zone's side setback is larger than 4 ft.

• ›800 sq ft ADU: 4 ft side setbacks leave 60 minus 8 = 52 ft of buildable width. A 25 by 32 ft footprint fits easily.
• ›1,000 sq ft ADU: the unit falls in the 800 to 1,200 sq ft band, so the underlying zone setbacks apply instead of 4 ft. The buildable area shrinks, and on a narrow lot the larger unit may not fit where the smaller one would.

Costs, based on ADUByCity city data, as of 2026: Escondido build costs run $220–$290 per sq ft, so the 800 sq ft unit is about $176,000–$232,000 and the 1,000 sq ft unit about $220,000–$290,000. Both units are over 750 sq ft, so both pay pro-rated impact fees (Escondido waives them only under 750 sq ft), and both pay school fees because they exceed 500 sq ft. Test layouts with the size calculator and price them with the cost calculator.

What changed for ADUs with SB 543 in 2025?

SB 543 did not change the 4 ft cap. The changes that matter for a setback-driven project are timing and fees:

• ›The city has 15 business days to say whether your application is complete, or it is deemed complete, then 60 days to approve or deny it (Gov. Code §66317).
• ›ADUs and JADUs of 500 sq ft or less are exempt from school impact fees (Gov. Code §66324).

If setbacks push you to a smaller unit, 500 sq ft or less now avoids school fees too. See the ADU permit process.

How are ADU setbacks measured?

From the property line, not the fence, to the nearest point of the structure, usually the wall rather than the roof edge. You cannot build in an easement, so check your title report.

When in doubt, hire a surveyor to mark your corners. Fences are not reliable property lines.

Can lot coverage or height rules block an ADU?

Not below the state minimum. Lot coverage, floor area ratio, and open space rules cannot prevent an 800 sq ft ADU with 4 ft side and rear setbacks. Height minimums are also set by state law: at least 16 ft for a detached ADU, 18 ft within half a mile of major transit or on a multifamily lot (plus 2 ft to match the main home's roof pitch), and 25 ft or the zone limit for attached ADUs. For multifamily lots, see ADUs on multifamily property.

Check your city's page, compare nearby cities on the compare page, and read California ADU laws for the rest of the state baseline.

Sources

• ›Gov. Code §66314: ADU standards, including 4 ft setbacks
• ›Gov. Code §66321: 800 sq ft minimum ADU and height
• ›Gov. Code §66317: permit timelines (SB 543)
• ›Gov. Code §66324: impact and school fees (SB 543)
• ›HCD ADU Handbook
• ›City of Escondido: Accessory Dwelling Units
• ›City of Riverside: ADU Information
• ›Cost ranges: ADUByCity city data, as of 2026