420 San Geronimo Valley Dr
San Geronimo 94963 · San Geronimo Village · Unincorporated Marin · Coordinates: 38.01172, -122.65943
Executive Verdict · Public-Records Synthesis
Zoned R1-B4-SGV in Unincorporated Marin with likely ADU & SB 9 infill eligibility and mapped CAL FIRE high fire hazard severity zone (state responsibility area) due diligence; benchmark value $1,387,000 ($1,221,000–$1,553,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1-B4-SGV supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 70,306 sq ft lot. Local precedent is active with 1 ADU permit within ¼ mile over the last 36 months.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ Documented permitted upgrades (+$6,264 contributory est.)
Public building records show issued construction/renovation work on this parcel (3 total permits, latest Feb 9, 2026).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
Watchouts & Due Diligence
- ! Mapped flood awareness zone (Zone X: minimal flood hazard)
all of the lot of the parcel intersects Zone X: minimal flood hazard. Outside mandatory federal SFHA insurance rules, but check local drainage and finished-floor requirements.
Source: FEMA National Flood Hazard Layer (parcel polygon)
- ! CAL FIRE High Fire Hazard Severity Zone (State Responsibility Area) (all of the lot of lot)
Located in a mapped Fire Hazard Severity Zone. Expect Chapter 7A ignition-resistant building standards, defensible-space inspections, and stricter property insurance underwriting.
Source: CAL FIRE FHSZ (map Apr 1, 2024)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: Demolition at 16 Meadow View Ln (0.23 mi SE, applied). Inspect timeline history before assuming near-term completion.
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · HCD APR (½-mile radius)
- ! Year 1 Prop 13 tax reset (~$16,401/yr at $1,387,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,367/mo). Confirm exact Mello-Roos / CFD special assessments on the county tax bill.
Source: CA Const. Art. XIIIA (Prop 13) · County Tax Collector
Parcel & Assessor
- Lot size:
- 70,306 sq ft (1.61 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 420 SAN GERONIMO VALLEY DR
Zoning & Land Use
R1-B4-SGV — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1-B4-SGV (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1-B4-SGV, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1-B4-SGV, a single-family residential zone. The lot is 70,306 sq ft by the assessor, room for two lots of at least 1,200 sq ft, each at least 40% of the original.
Mapped Hazard Zones on This Lot
- CAL FIRE Fire Hazard Severity Zone
- High Fire Hazard Severity Zone (State Responsibility Area) (all of the lot, map Apr 1, 2024)
- FEMA National Flood Hazard Layer
- Zone X: minimal flood hazard (all of the lot) · FIRM panel 06041C0275D, effective May 4, 2009
- CGS Alquist-Priolo Earthquake Fault Zone
- Not in an Alquist-Priolo Earthquake Fault Zone
Surrounding Rent & Value Benchmarks (Public Records)
Range: $1,221,000 – $1,553,000 · Status: Off market
HUD Small Area FMR (ZIP 94963) · FY 2026
Studio $2,500 · 1BR $3,000 · 2BR $3,630 · 3BR $4,630 · 4BR $4,800
Developments Deserving Closer Investigation & Active Area Builders
- Demolition at 16 Meadow View Ln (Applied)0.23 mi SE
In "Applied" for 8.5 yr (since May 29, 2018), exceeding the 55d median and 261d 90th percentile for demolition permits in Unincorporated Marin (n=130).
- New home at 16 Meadow View Ln (Issued)0.23 mi SE
Active in "Issued" for 17.9 yr (first record Dec 23, 2008) with no new permit activity recorded in 12.5 yr.
- New home at 18 Meadow View Ln (Issued)0.23 mi SE
Active in "Issued" for 17.9 yr (first record Dec 23, 2008) with no new permit activity recorded in 12.5 yr.
- Accessory dwelling unit at 12 Meadow View Ln (Issued)0.23 mi SE
Active in "Issued" for 23 mo (first record Dec 19, 2024) with no new permit activity recorded in 23 mo.
Entity-resolved builders & contractors in ½ mile: A1 Solar Power (1 on parcel, 1 in ½ mi · Solar / battery storage); Sameday Plumbing Heating And Cooling (1 on parcel, 1 in ½ mi · Other); Canopy Energy (1 on parcel, 1 in ½ mi · Electrical / panel); Owner Builder (4 in ½ mi · Demolition); Juan Calmell (3 in ½ mi · New single-family home).
Permit & Project History on This Parcel (3 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B45791 | Other | Issued | Iss. Feb 9, 2026 | $4,500 | Replace Mechanical Appliance |
| 154465 | Electrical / panel | Issued | Iss. Feb 1, 2017 | $1,500 | Upgrade Main Panel 100 A To 125 A (Actual Scope To Install 100a Sub Pnl) |
| 154210 | Solar / battery storage | Issued | Iss. Dec 27, 2016 | $23,200 | P V Sys 4.64 K W - Express |