Castro Valley 94546 · Castro Valley · APN 84D-1341-41 · Unincorporated Alameda County
Since — within ½ mile: 4 permitted.
4 projects with a record in this window, grouped by us from permits and State housing reports. Units are as proposed on each project's latest record and counted at its current stage.
No permit activity recorded within ½ mile.
$1,008,000
Benchmark range: $887,000 – $1,129,000
Public-records benchmark estimate combining Zillow Home Value Index (Data provided by Zillow), Census ACS 5-year estimates, parcel land-use/lot characteristics, and issued building permits. Not an official appraisal.
We don't have building permits for Unincorporated Alameda County, so we can't show what has been permitted nearby.
Permit counts, by the date issued (or applied, if not yet issued). Lot splits are planning cases, which we don't have.
We read public zoning and hazard maps against state law (ADUs: Gov. Code 66314; SB 9: Gov. Code 65852.21 and 66411.7). Local rules, title, tenancy history and site conditions can change the answer. Check with Unincorporated Alameda County's planning department before relying on it.
Sources: City of Oakland Planning & Building, Zoning (base zones, effective 2024-12-17) (retrieved Oct 26, 2026) · CAL FIRE Office of the State Fire Marshal, Fire Hazard Severity Zones in the State Responsibility Area (effective 2024-04-01) (retrieved Oct 26, 2026) · CAL FIRE Office of the State Fire Marshal, Fire Hazard Severity Zones in the Local Responsibility Area (map dated 2025-03-24) (retrieved Oct 26, 2026) · FEMA, National Flood Hazard Layer — flood hazard zones (retrieved Oct 26, 2026) · FEMA, National Flood Hazard Layer — FIRM panels (retrieved Oct 26, 2026) · California Geological Survey, Alquist-Priolo Earthquake Fault Zones (retrieved Oct 26, 2026)
Chronological history of building permit applications and issuances, snapshot-dated status changes, State housing entitlements, surrounding development within ½ mile, and area home-value trends.
Permit issued and active for 4.3 yr (first record Aug 1, 2022), with no completion or new permit record in 4.3 yr. · 1 unit
Permit issued and active for 3.8 yr (first record Jan 23, 2023), with no completion or new permit record in 3.8 yr. · 1 unit
Permit issued and active for 3.6 yr (first record Apr 15, 2023), with no completion or new permit record in 3.6 yr. · 1 unit
Permit issued and active for 3.4 yr (first record May 30, 2023), with no completion or new permit record in 3.4 yr. · 1 unit
Permit issued and active for 3.1 yr (first record Oct 10, 2023), with no completion or new permit record in 3.1 yr. · 1 unit
Permit issued and active for 3 yr (first record Nov 16, 2023), with no completion or new permit record in 3 yr. · 1 unit
Latest published Zillow Home Value Index (ZHVI) update
Changed from $991,965 in September 2025 to $1,006,862 in September 2026.
Source: Zillow Home Value Index (ZHVI) · Data provided by Zillow · Geography: ZIP 94546 (not a parcel appraisal)
Building permit reported to State HCD for 1 housing unit (BLD2025-01557)
Reported in 2025 Housing Element Annual Progress Report
ADU · Renter
Source: California HCD, Housing Element Annual Progress Report — Table A2 · Geography: parcel
Annual ZIP 94546 home-value index checkpoint
Changed from $1,041,669 in September 2024 to $991,965 in September 2025.
Source: Zillow Home Value Index (ZHVI) · Data provided by Zillow · Geography: ZIP 94546 (not a parcel appraisal)
1 unit
Source: Alameda County building permits & HCD APR (grouped project within ½ mile)
1 unit
Source: Alameda County building permits & HCD APR (grouped project within ½ mile)
Planning entitlement approved for 1 housing unit (BLD2025-01557)
Reported in 2025 Housing Element Annual Progress Report
ADU · Renter
Source: California HCD, Housing Element Annual Progress Report — Table A2 · Geography: parcel
1 unit
Source: Alameda County building permits & HCD APR (grouped project within ½ mile)
1 unit
Source: Alameda County building permits & HCD APR (grouped project within ½ mile)
1 unit
Source: Alameda County building permits & HCD APR (grouped project within ½ mile)
Annual ZIP 94546 home-value index checkpoint
Changed from $986,080 in September 2023 to $1,041,669 in September 2024.
Source: Zillow Home Value Index (ZHVI) · Data provided by Zillow · Geography: ZIP 94546 (not a parcel appraisal)
1 unit
Source: Alameda County building permits & HCD APR (grouped project within ½ mile)
1 unit
Source: Alameda County building permits & HCD APR (grouped project within ½ mile)
1 unit
Source: Alameda County building permits & HCD APR (grouped project within ½ mile)
Source: Alameda County building permits & HCD APR (grouped project within ½ mile)
1 unit
Source: Alameda County building permits & HCD APR (grouped project within ½ mile)
Cross-referenced intelligence from our historical development graph—connecting parcels, permits, entity-resolved builders, empirical review-time distributions, and neighborhood renovation trends.
Explore full Unincorporated Alameda County development graph →Active in "Issued" for 18 mo (first record Apr 23, 2025) with no new permit activity recorded in 18 mo.
Active in "Issued" for 4.3 yr (first record Aug 1, 2022) with no new permit activity recorded in 4.3 yr.
Active in "Issued" for 3.4 yr (first record May 30, 2023) with no new permit activity recorded in 3.4 yr.
Active in "Issued" for 3.8 yr (first record Jan 23, 2023) with no new permit activity recorded in 3.8 yr.
Active in "Issued" for 16 mo (first record Jul 8, 2025) with no new permit activity recorded in 16 mo.
Active in "Issued" for 18 mo (first record May 12, 2025) with no new permit activity recorded in 18 mo.
HUD Small Area Fair Market Rent · ZIP 94546
HUD FY 2026 · 40th-percentile gross rentCensus ACS 5-year median gross rent (all bedroom counts combined):
Area home-value benchmarks (not an appraisal)
ZIP & neighborhood mediansUnder California Proposition 13, the seller's historical assessed value does not carry over to a buyer. On sale, the parcel is reassessed at the purchase price: 1.00% base rate ($10,100/yr) + local voter-approved bond debt ($2,222/yr) + fixed direct levies/Mello-Roos ($450/yr).
Insurance & hazard context:
−$48,173/yr
Cash needed: $222,200
NOI: $13,112/yr
P&I: $5,107/mo
For $0/mo net cash flow
At $3,000/mo rent
| Scenario | Assumptions | Year 1 Rent | Year 1 Cash Flow | Cash-on-Cash | Break-Even Rent | Year 5 Cash Flow |
|---|---|---|---|---|---|---|
| Conservative | −8% starting rent, +3% vacancy, +3% combined maintenance/CapEx, 1.5%/yr rent growth | $2,760/mo | −$4,359/mo | -23.5% | $8,845/mo | −$4,340/mo |
| Base (your inputs) | Your entered assumptions, 3.0%/yr rent growth | $3,000/mo | −$4,014/mo | -21.7% | $8,187/mo | −$3,825/mo |
| Optimistic (cap-limited) | +6% starting rent, 3% vacancy, 4.5%/yr rent growth (capped by AB 1482 ceiling of 8.6%/yr) | $3,180/mo | −$3,817/mo | -20.6% | $7,997/mo | −$3,433/mo |
Rental regulatory context (informational only — not legal advice):
California AB 1482 (Tenant Protection Act, Civ. Code § 1947.12) caps annual rent increases at 5% + local CPI (max 10%) on covered properties.
Issued1 unitsApr 23, 2025 – Apr 23, 2025
We group related permits and State housing reports into projects. That grouping is our inference, not an official record.
No building permits are recorded for this parcel since 2016.
| Report year | Project / record | Type | Entitled | Permitted | Completed | Deed-restricted |
|---|---|---|---|---|---|---|
| 2025 | —(BLD2025-01557) | ADU · Renter | 1 (Apr 23, 2025) | 1 (Nov 5, 2025) | — | — |
Source: California HCD, Housing Element Annual Progress Report — Table A2 · Geography: project (parcel) · Retrieved Oct 26, 2026 · From Unincorporated Alameda County's Housing Element Annual Progress Reports. A project can appear in several report years as it moves from entitlement to permit to completion.
Source: City of Oakland Planning & Building, Zoning (base zones, effective 2024-12-17) · Geography: zoning district polygon at parcel point · Retrieved Oct 26, 2026
0.09 acres
Assessor's classification for assessment purposes. This is not zoning.
18921 PATTON DR; 18921 PATTON DR UNIT A
Source: Alameda County Assessor / Information Technology Department, Parcel Boundaries · Geography: parcel · Retrieved Oct 26, 2026
Look up assessed values and parcel maps by parcel number 84D-1341-41. Assessed value is not market value.
Search by parcel number 84D-1341-41 (Alameda County Treasurer-Tax Collector)
The official flood hazard map for this location. Our reading of it is under What could be built here.
This site does not show owner names.