Alameda County R-3 zoning: height, setbacks and lot size

R-3 is a zoning district in Alameda County. Every value below was read from the Alameda County Municipal Code and links to its section (read October 2026). State laws such as the ADU and SB 9 rules can allow more on a residential lot. General information, not legal advice — read the code text and check with the city before you build.

Development standards in R-3

The general rule for a typical lot in this zone. Zoning tables often attach notes, such as rules for corner lots, lots next to a residential zone, or new subdivisions only. Open “code text” under a value to see the table cell or sentence it was read from.

Maximum building height	25 ft Applies: Any building or structure § 17.14.070 · code text No dwelling shall have a height of more than two stories, except as provided by Section 17.52.090; nor shall any building or structure have a height in excess of twenty-five (25) feet, except as provided by Section 17.52.090.
Maximum number of stories	2 stories Applies: Dwelling § 17.14.070 · code text No dwelling shall have a height of more than two stories, except as provided by Section 17.52.090; nor shall any building or structure have a height in excess of twenty-five (25) feet, except as provided by Section 17.52.090.
Minimum front setback	20 ft § 17.14.060 · code text Depth of front yard: Not less than twenty (20) feet;
Minimum side setback	5 ft plus 1 ft for each full 10 ft by which median lot width exceeds 50 ft, up to 10 ft; in no case less than 6 ft Applies: Interior side yard at least 6 ft; street side of a corner lot at least 10 ft § 17.14.060 · code text Width of side yard: Not less than five feet plus one foot for each full ten feet by which the median lot width exceeds fifty (50) feet up to a maximum requirement of ten feet, but in no case less than six feet for an interior side yard or less than ten feet on the street side of a corner lot, or less than required by Section 17.14.080.
Minimum rear setback	20 ft § 17.14.060 · code text Depth of rear yard: Not less than twenty (20) feet;
Maximum density	1 unit per 2,000 sq ft Applies: No more than four units per lot; the four-unit limit does not apply in Castro Valley § 17.14.040 · code text The number of dwelling units on a lot or building site in an R-3 district shall not exceed one for each full two thousand (2,000) square feet of the area thereof, or be in any case more than four.

When a different number applies

The code sets other values for particular lots, buildings or locations in R-3:

Maximum density: 4 units per lot — Outside Castro Valley (areas within the Castro Valley Urbanized Area) § 17.14.040

Not on this page

We did not find a general lot size, lot coverage, FAR limit for R-3 in the zoning tables we read. The code may still set one elsewhere — check the Alameda County Municipal Code.

Other Alameda County zoning districts

Who this affects

HomeownersArchitects and designersDevelopersReal estate agents

Frequently asked questions

What is the maximum building height in Alameda County's R-3 zone?

25 ft (any building or structure) — Alameda County Municipal Code § 17.14.070.

What is the maximum number of stories in Alameda County's R-3 zone?

2 stories (dwelling) — Alameda County Municipal Code § 17.14.070.

What is the minimum front setback in Alameda County's R-3 zone?

20 ft — Alameda County Municipal Code § 17.14.060.

What is the minimum side setback in Alameda County's R-3 zone?

5 ft plus 1 ft for each full 10 ft by which median lot width exceeds 50 ft, up to 10 ft; in no case less than 6 ft (interior side yard at least 6 ft; street side of a corner lot at least 10 ft) — Alameda County Municipal Code § 17.14.060.

What is the minimum rear setback in Alameda County's R-3 zone?

20 ft — Alameda County Municipal Code § 17.14.060.

General information, not legal advice.