18 Main St
San Quentin 94964 · San Quentin · Unincorporated Marin · Coordinates: 37.94205, -122.48238
Executive Verdict · Public-Records Synthesis
Zoned RMP-11.7 in Unincorporated Marin with likely ministerial ADU eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $1,498,000 ($1,273,000–$1,723,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone RMP-11.7 allows residential use qualifying for ministerial ADU review under state law.
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ Documented permitted upgrades (+$43,340 contributory est.)
Public building records show issued construction/renovation work on this parcel (12 total permits, latest Oct 28, 2023).
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)
- ! Delayed or open permit activity on this parcel
Remodel / interior alteration (173802): Issued after 22 mo (8.0× the 83d median) — slower than 90% of remodel / interior alteration permits in Unincorporated Marin (median 83d, 90th pct 266d, n=1,054).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (review-time benchmark)
- ! 1 slow or stalled nearby project within ½ mile
Closest lead: New home at 22 Mckenzie St (340 ft W, issued). 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 (~$17,677/yr at $1,498,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,473/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:
- 11,326 sq ft (0.26 ac)
- Assessor use:
- Multiple-Resid. - Improved
- Addresses on lot:
- 18 MAIN ST; 18 MAIN ST A; 20 MAIN ST
Zoning & Land Use
RMP-11.7 — Residential Multiple Planned (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned RMP-11.7 (multifamily residential): state law allows ADUs where homes are allowed. On a multifamily lot the state allowance is different: ADUs in non-living space of the building, plus up to eight detached ADUs.
- SB 9: two homes on the lotUnlikely
Zoned RMP-11.7 (multifamily residential), not a single-family residential zone.
- SB 9: split into two lotsUnlikely
Zoned RMP-11.7 (multifamily residential), not a single-family residential zone.
Mapped Hazard Zones on This Lot
- CAL FIRE Fire Hazard Severity Zone
- Not in a State-mapped fire hazard severity zone
- FEMA National Flood Hazard Layer
- Zone X: minimal flood hazard (all of the lot) · FIRM panel 06041C0478E, effective March 16, 2016
- CGS Alquist-Priolo Earthquake Fault Zone
- Not in an Alquist-Priolo Earthquake Fault Zone
Surrounding Rent & Value Benchmarks (Public Records)
Range: $1,273,000 – $1,723,000 · Status: Off market
HUD Small Area FMR (ZIP 94964) · FY 2026
Studio $2,530 · 1BR $3,040 · 2BR $3,680 · 3BR $4,700 · 4BR $4,870
Nearby Activity (½ mile radius, since November 2024)
0 active or recent development projects and 12 total building permits recorded within ½ mile.
- Additions & renovations2 permits
- Building systems8 permits
Developments Deserving Closer Investigation & Active Area Builders
- Remodel / interior alteration (173802) (Issued)On this parcel
Issued after 22 mo (8.0× the 83d median) — slower than 90% of remodel / interior alteration permits in Unincorporated Marin (median 83d, 90th pct 266d, n=1,054).
- New home at 22 Mckenzie St (Issued)340 ft W
Active in "Issued" for 3.9 yr (first record Dec 27, 2022) with no new permit activity recorded in 2.8 yr. High-impact scale (1 housing unit, $850,000 declared valuation across 1 permit).
Entity-resolved builders & contractors in ½ mile: Owner (7 on parcel, 7 in ½ mi · Electrical / panel); James Flanagan Builder (2 on parcel, 2 in ½ mi · New garage / accessory structure); Owner Builder (1 on parcel, 1 in ½ mi · Remodel / interior alteration); Flanagan James Builder (1 on parcel, 1 in ½ mi · New garage / accessory structure); Ja Roofing (1 on parcel, 1 in ½ mi · Roof replacement).
Permit & Project History on This Parcel (12 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B35933 | Electrical / panel | Issued | Iss. Oct 28, 2023 | $2,000 | Like for like replacement of electric panels for Units 18 and 20. — Replace Circuits / Outlets |
| 173802 | Remodel / interior alteration | Issued | Iss. Apr 14, 2023 | $75,000 | Remodel Apartment - Express **Application Extended To 8/11/23; Nh/Bbw |
| B31672 | EV charger | Issued | Iss. Nov 15, 2022 | $5,000 | EV charging dual ports — EV Charging Station |
| 157066 | New garage / accessory structure | Issued | Iss. Nov 15, 2017 | $36,000 | ew Laundry Room (Detached) (Includes Separage Electrical And Gas Meter) T.D. 3/20/17. |
| B12764 | Roof replacement | Issued |