Alameda County · Zoning · R-1
Alameda County R-1 zoning: height, setbacks and lot size
In Alameda County's R-1 zone, generally buildings can be up to 25 ft (2 stories) tall and the front setback is 20 ft, with the conditions listed below (Alameda County code, read October 2026).
Key points
- Maximum building height: 25 ft (Any building or structure)
- Maximum number of stories: 2 stories (Dwelling)
- Minimum front setback: 20 ft
- 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 (Interior side yard; the street side of a corner lot needs at least 10 ft)
- Minimum rear setback: 20 ft
- Maximum floor area ratio (FAR): 0.5 FAR (Castro Valley Urbanized Area; one-family dwelling; lot size at 5,000 s.f.)
- Maximum density: 5.5 units per project acre
R-1 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-1
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 § 17.08.100 · code textNo 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 for in this section and by Section 17.52.090. |
|---|---|
| Maximum number of stories | 2 stories Applies: Dwelling § 17.08.100 · code textNo 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 for in this section and by Section 17.52.090. |
| Minimum front setback | 20 ft § 17.08.070 · code textA. Depth of front yard: 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 Applies: Interior side yard; the street side of a corner lot needs at least 10 ft § 17.08.070 · code textC. Width of side yards: 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, except that in every case the side yard on the street side of a corner lot shall have a width not less than ten feet. |
| Minimum rear setback | 20 ft § 17.08.070 · code textB. Depth of rear yard: Twenty (20) feet; |
| Maximum floor area ratio (FAR) | 0.5 FAR Applies: Castro Valley Urbanized Area; one-family dwelling; lot size at 5,000 s.f. See note 2 below the table in the code. § 17.08.110 · code textTable row “At 5,000 s.f.”, column “Maximum FAR Formula 2”: 0.5 FAR Note 2: Floor area ratio (FAR) is the total square feet of floor area divided by the total square feet of lot area. Floor area excludes areas devoted to parking, garages and covered porches/patios, and areas located below finished grade, if the ceiling does not extend more than five feet above finished grade. |
| Maximum density | 5.5 units per project acre § 17.54.460 · code textTable row “R-1”, column “Maximum Units Per Project Acre”: 5.5 |
When a different number applies
The code sets other values for particular lots, buildings or locations in R-1:
- Maximum building height: Up to 30 ft: the 25 ft limit rises 2 ft for each full 10 ft of median lot width over 70 ft — Dwelling only; median lot depth at least 100 ft, median lot width at least 70 ft, effective lot frontage at least 50 ft § 17.08.100
- Minimum side setback: 10 ft — A dwelling's front or living room entrance opens into a side yard extending from the entrance to the front yard § 17.08.090
- Minimum rear setback: 10 ft — The part of the rear yard under 20 ft deep must be made up by extra open area in the same or adjacent yards § 17.08.080
- Maximum floor area ratio (FAR): 0.40 FAR — Castro Valley only; one-family dwelling on a lot of 10,000 to 20,000 sq ft; or 4,500 sq ft, whichever is less § 17.08.110
- Maximum floor area ratio (FAR): 0.10 FAR, plus 2,500 s.f. — Castro Valley only; one-family dwelling on a lot over 20,000 sq ft; capped at 10,000 sq ft total § 17.08.110
Not on this page
We did not find a general lot size, lot coverage limit for R-1 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
Frequently asked questions
What is the maximum building height in Alameda County's R-1 zone?
25 ft (any building or structure) — Alameda County Municipal Code § 17.08.100.
What is the maximum number of stories in Alameda County's R-1 zone?
2 stories (dwelling) — Alameda County Municipal Code § 17.08.100.
What is the minimum front setback in Alameda County's R-1 zone?
20 ft — Alameda County Municipal Code § 17.08.070.
What is the minimum side setback in Alameda County's R-1 zone?
5 ft plus 1 ft for each full 10 ft by which median lot width exceeds 50 ft, up to 10 ft (interior side yard; the street side of a corner lot needs at least 10 ft) — Alameda County Municipal Code § 17.08.070.
What is the minimum rear setback in Alameda County's R-1 zone?
20 ft — Alameda County Municipal Code § 17.08.070.
General information, not legal advice.
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