Alameda County property record for 4278 Gem Ave, Castro Valley, CA 94546
| Property Type | Single Family Home |
|---|---|
| Details | 2 bd · 1 ba · 984 sqft · built 1947 |
| Lot Size | 0.137 acres (5,985 sqft) |
| Owner | Individual Name on File |
| Last Sale | $395,000 (Nov 2003) |
| Tax Bill | $7,413 (2025) |
| Flood Zone | Zone X (minimal risk) |
| APN | 84C-669-25 |
| Primary APN | 84C-669-25 |
|---|---|
| Alternative APN |
|
| Bedrooms | 2 Beds |
|---|---|
| Full Baths | 1 Bath |
| Total Rooms | 5 Rooms |
| Stories | 1 Story |
| Building Area | 984 sqft Living Area |
| Year Built | Built 1947 |
|---|---|
| Effective Year Built | Effective 1947 |
| Architectural Style | L-Shape |
| Construction Type | Wood |
| Lot Area | 5,985 sqft (0.137 acres) |
| Street Address | 4278 GEM AVE |
|---|---|
| City | CASTRO VALLEY |
| State | CA |
| Zip | 94546-4617 |
| Property Category | Residential |
| Property Type | Residential > Single Family > Home |
| Legal Description | LOT: 00014 BLK: 0001 TR: 0807 |
| Legal Tract | 0807 |
| Legal Block | 1 |
| Legal Lot Number | 14 |
| Jurisdiction | ALAMEDA CA |
| Township / Civil Division | HAYWARD |
| Census Block Group | 4 |
| Census Block | 4000 |
| Census Tract | 430800 |
4278 Gem Ave is owned and occupied by an individual who acquired it in July 2007.
Source: Alameda County records, as of August 5, 2026
Owner names and exact recorded amounts are on file and can be viewed instantly on this page with a free 10-day trial.
| Owner of Record | Individual Name on File |
|---|---|
| Mailing Address | 4278 GEM AVE, CASTRO VALLEY, CA 94546-4617 |
| Occupancy | Owner Occupied |
| Owner Type | Individual |
| Vesting | Single Person |
| Deed Names | Name on Deed |
|---|---|
| Last Sale | Nov 19, 2003 · Amount on File |
| Deed Sale | Nov 19, 2003 · Amount on File |
| Prior Sale | Nov 29, 2001 · Amount on File |
| Deed Document Number | 2003683606 |
| Last Transfer Date | Jul 20, 2007 |
| Transfer Doc | 0000312507 |
| Record Updated | Oct 29, 2026 |
The 2025 property tax bill for 4278 Gem Ave was $7,413 with a homeowner's exemption.
Source: Alameda County assessment roll, as of August 5, 2026
| Type | Name |
|---|---|
| State | California |
| County | Alameda County |
| Unified School District | Castro Valley Unified School District (KG - 12) |
| Year | Tax Bill | Assessed Value | Assessed Market Value |
|---|---|---|---|
| 2026 | $565,804 (+0.75%) Land $171,841 Building $400,963 | ||
| 2025 | $7,413.00 Homeowner's exemption | $561,574 Land $168,472 Building $393,102 | |
| 2023 | $7,119.00 Homeowner's exemption | $539,771 Land $161,931 Building $377,840 | $790,380 |
Assessed value and assessed market value are set for property tax purposes and are not market price estimates.
FEMA maps place 4278 Gem Ave in Zone X, an area of minimal flood risk.
Source: FEMA National Flood Hazard Layer, effective May 25, 2026 · OpenFEMA NFIP redacted claims and policies, as of September 2026
| FEMA Flood Zone | Zone X minimal risk |
|---|---|
| Flood Insurance Requirement | Not required lenders may require it |
| Community Rating System | Class 7 (15% premium discount) |
| Nearby Flood Policies | 1 in force |
Values are read at the parcel center point; flood claims are located to the census block group, not this parcel; lenders make the official flood determination.
Wildfire risk around 4278 Gem Ave is low, with a 0.01% annual chance of wildfire.
Source: USDA Forest Service Wildfire Risk to Communities (2nd edition), as of 2024
| Wildfire Risk | Low lower than 80% of the US · lower than 88% of California |
|---|---|
| Wildfire Likelihood | 0.01% annual chance |
| Exposure | None beyond ember reach |
Values cover an area roughly 900 ft across, not the parcel itself; insurers use their own ratings.
Source: EPA Safe Drinking Water Information System, as of September 2026
| Water System | EAST BAY MUD serves 1,468,000 people · EPA ID CA0110005 |
|---|---|
| Water Source | Surface water |
| Last State Inspection | Dec 2021 |
| Lead | Under 1 ppb (2022–2024) action level 15 ppb |
| Water Quality | None last 10 years |
|---|---|
| Treatment and Procedure | None last 10 years |
| Monitoring and Reporting | None last 3 years |
Results are for the whole water system, not water tested at this address; lead at the tap also depends on the building's own pipes. This system sells water to local utilities; the supplier billing this address may be one of them.
Source: FCC Broadband Data Collection, based on 777 locations within half a mile, as of December 31, 2025
| Provider | Max Down / Up (Mbps) |
|---|---|
| Sonic Telecom Fiber | 10,000 / 10,000 |
| AT&T Fiber · DSL · Fixed Wireless in parts of the area | 5,000 / 5,000 |
| Xfinity Cable | 2,000 / 250 |
| Verizon Fixed Wireless | 300 / 20 |
| Etheric Networks Fixed Wireless | 250 / 100 |
| T-Mobile Fixed Wireless | 100 / 20 |
May also be available: GeoLinks.
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