Structure Height Limits: Castro Valley vs Fremont
How do structure height limits rules compare between Castro Valley, CA and Fremont, CA?
Castro Valley has fewer restrictions than Fremont.
Castro Valley, CA
Alameda County
Alameda County limits residential structure heights to 30-35 feet in most R-1 zones under Title 17, with stricter limits in hillside overlays. ADUs are capped at 16-18 feet per state law.
View full Castro Valley rules →Fremont, CA
Alameda County
Fremont limits single-family homes to 30 feet or 2 stories in most R-1 zones, with hillside overlay districts imposing stricter limits to protect ridgelines.
View full Fremont rules →Key Facts Comparison
| Fact | Castro Valley | Fremont |
|---|---|---|
| R-1 height limit | 30 feet / 2.5 stories typical | - |
| Hillside zones | Often 25 feet maximum | - |
| Detached ADU | 16 feet (state law) | - |
| Measured from | Average natural grade | - |
| Rooftop equipment | May exceed with conditions | - |
| R-1 Height | - | 30 feet / 2 stories |
| Accessory | - | 15 feet |
| ADU Height | - | 25 feet (state law) |
| Hillside | - | Stricter overlay limits |
| Contact | - | (510) 494-4455 |
Highlighted rows indicate differences between cities.
Castro Valley FAQ
Does a basement count toward height?
Generally no if it is below average natural grade, but a daylight basement that extends above grade on downslope sides may count as a story depending on exposure.
Can I add a second story to my Castro Valley home?
Yes if the finished structure stays within the zone height limit and does not violate hillside overlay restrictions. A building permit and often design review are required.
Fremont FAQ
Can I build a three-story home?
Not in standard R-1 zones; multi-family or specific plan areas may allow 3 stories with design review.
Do hillside rules apply to my lot?
Check the Fremont Hillside Combining District map; lots in the overlay have ridgeline and height protections.
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