140 St Thomas Way
Tiburon 94920 · Paradise Cay · Unincorporated Marin · Coordinates: 37.91280, -122.47478
Executive Verdict · Public-Records Synthesis
Zoned RSP-5.8-BFC in Unincorporated Marin with likely ADU & SB 9 infill eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $3,050,000 ($2,684,000–$3,416,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned RSP-5.8-BFC supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 7,362 sq ft lot.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ Documented permitted upgrades (+$17,820 contributory est.)
Public building records show issued construction/renovation work on this parcel (6 total permits, latest Jul 7, 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)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: New home at 149 Jamaica St (520 ft SW, 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 (~$35,525/yr at $3,050,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,960/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:
- 7,362 sq ft (0.17 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 140 ST THOMAS WAY
Zoning & Land Use
RSP-5.8-BFC — Residential Single Family Planned (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned RSP-5.8-BFC (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned RSP-5.8-BFC, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned RSP-5.8-BFC, a single-family residential zone. The lot is 7,362 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
- 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 06041C0486E, 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: $2,684,000 – $3,416,000 · Status: Off market
HUD Small Area FMR (ZIP 94920) · FY 2026
Studio $2,820 · 1BR $3,380 · 2BR $4,100 · 3BR $5,230 · 4BR $5,420
Developments Deserving Closer Investigation & Active Area Builders
- New home at 149 Jamaica St (Issued)520 ft SW
Active in "Issued" for 12.2 yr (first record Aug 19, 2014) with no new permit activity recorded in 12 yr. High-impact scale (1 housing unit, $750,000 declared valuation across 1 permit).
- New home (Entitled)450 ft SW
In "Entitled" for 5.1 yr (since Oct 7, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- New home at 100 Jamaica St (Issued)0.21 mi S
Active in "Issued" for 11.4 yr (first record Jun 2, 2015) with no new permit activity recorded in 11.1 yr.
- New home at 225 Trinidad Dr (lot #9) (Issued)0.22 mi W
Active in "Issued" for 12.7 yr (first record Feb 12, 2014) with no new permit activity recorded in 12.3 yr.
Entity-resolved builders & contractors in ½ mile: Owner (2 on parcel, 13 in ½ mi · Remodel / interior alteration); Marinkitchenco (1 on parcel, 3 in ½ mi · Other); The Home Doctors (1 on parcel, 1 in ½ mi · Remodel / interior alteration); Wedge Roofing (1 on parcel, 1 in ½ mi · Roof replacement); Hulbert Heating And Air Conditioning (1 on parcel, 1 in ½ mi · Other).
Permit & Project History on This Parcel (6 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B47405 | Other | Issued | Iss. Jul 7, 2026 | $11,467 | Replace Mechanical Appliance |
| B47283 | Other | Issued | Iss. Jun 24, 2026 | $105,000 | — |
| B17909 | Electrical / panel | Issued | Iss. Jun 3, 2019 | $1,000 | Replace current Zinsco fuse box in utility room with like fuse box in same location per dialog on record with Tiburon De… |
| B17666 | Windows / doors / siding | Issued | Iss. May 2, 2019 | $5,000 | Partial repair and replacement of stucco on west side of home — Stucco Replacement |
| 160690 | Remodel / interior alteration | Issued | Iss. Feb 5, 2019 |