18135 State Route 1
Marshall 94940 · East Shore · Unincorporated Marin · Coordinates: 38.14106, -122.87451
Executive Verdict · Public-Records Synthesis
Zoned C-RSP-0.33 in Unincorporated Marin with likely ministerial ADU eligibility and mapped FEMA AE flood / CAL FIRE moderate fire hazard severity zone (state responsibility area) due diligence; benchmark value $1,829,000 ($1,610,000–$2,048,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone C-RSP-0.33 allows residential use qualifying for ministerial ADU review under state law.
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ Documented permitted upgrades (+$81,000 contributory est.)
Public building records show issued construction/renovation work on this parcel (1 total permit, latest Jan 24, 2019).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
Watchouts & Due Diligence
- ! FEMA Special Flood Hazard Area (AE, about 54% of the lot of lot)
Zone AE: 1% annual chance flood (Special Flood Hazard Area) overlaps this parcel. Expect mandatory flood insurance for federally backed loans and floodplain elevation/mitigation rules for new units or SB 9 applications.
Source: FEMA National Flood Hazard Layer (parcel polygon)
- ! CAL FIRE Moderate Fire Hazard Severity Zone (State Responsibility Area) (about 75% 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)
- ! Year 1 Prop 13 tax reset (~$21,484/yr at $1,829,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,790/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:
- 23,392 sq ft (0.54 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 18135 STATE ROUTE 1
Zoning & Land Use
C-RSP-0.33 — Residential Single Family Planned (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned C-RSP-0.33 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotPossible, with conditions
Zoned C-RSP-0.33, a single-family residential zone. FEMA Special Flood Hazard Area (Zone AE) covers about 54% of the lot: the project must meet the National Flood Insurance Program floodplain standards, or the lot needs a map revision.
- SB 9: split into two lotsPossible, with conditions
Zoned C-RSP-0.33, a single-family residential zone. The lot is 23,392 sq ft by the assessor, room for two lots of at least 1,200 sq ft, each at least 40% of the original. FEMA Special Flood Hazard Area (Zone AE) covers about 54% of the lot: the project must meet the National Flood Insurance Program floodplain standards, or the lot needs a map revision.
Mapped Hazard Zones on This Lot
- CAL FIRE Fire Hazard Severity Zone
- Moderate Fire Hazard Severity Zone (State Responsibility Area) (about 75% of the lot, map Apr 1, 2024)
- FEMA National Flood Hazard Layer
- Zone AE: 1% annual chance flood (Special Flood Hazard Area) (about 54% of the lot); Zone AE: 1% annual chance flood (Special Flood Hazard Area) (about 37% of the lot); Zone X: minimal flood hazard (about 9% of the lot) · FIRM panel 06041C0115E, effective August 15, 2017
- CGS Alquist-Priolo Earthquake Fault Zone
- Not in an Alquist-Priolo Earthquake Fault Zone
Surrounding Rent & Value Benchmarks (Public Records)
Range: $1,610,000 – $2,048,000 · Status: Off market
HUD Small Area FMR (ZIP 94940) · FY 2026
Studio $2,050 · 1BR $2,510 · 2BR $2,990 · 3BR $3,870 · 4BR $4,090
Developments Deserving Closer Investigation & Active Area Builders
Entity-resolved builders & contractors in ½ mile: Owner Builder (1 on parcel, 1 in ½ mi · Addition (adds square footage)).
Permit & Project History on This Parcel (1 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| 160598 | Addition (adds square footage) | Issued | Iss. Jan 24, 2019 | $150,000 | Addn; Rmdl; Propane Tank; Deck W/Stairs; Pre Fab Hot Tub |