103 St Thomas Way
Tiburon 94920 · Paradise Cay · Unincorporated Marin · Coordinates: 37.91102, -122.47368
Executive Verdict · Public-Records Synthesis
Zoned RSP-5.8-BFC in Unincorporated Marin with likely ministerial ADU eligibility and mapped FEMA VE flood due diligence; benchmark value $3,291,000 ($2,896,000–$3,686,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone RSP-5.8-BFC allows residential use qualifying for ministerial ADU review under state law.
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ Documented permitted upgrades (+$126,480 contributory est.)
Public building records show issued construction/renovation work on this parcel (3 total permits, latest Jul 28, 2026).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
Watchouts & Due Diligence
- ! FEMA Special Flood Hazard Area (VE, about 44% of the lot of lot)
Zone VE: 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)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: New home at 149 Jamaica St (0.16 mi NW, 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 (~$38,297/yr at $3,291,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$3,191/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:
- 12,807 sq ft (0.29 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 103 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 lotPossible, with conditions
Zoned RSP-5.8-BFC, a single-family residential zone. FEMA Special Flood Hazard Area (Zone VE) covers about 44% 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 RSP-5.8-BFC, a single-family residential zone. The lot is 12,807 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 VE) covers about 44% 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
- Not in a State-mapped fire hazard severity zone
- FEMA National Flood Hazard Layer
- Zone VE: 1% annual chance flood (Special Flood Hazard Area) (about 44% of the lot); Zone X: 0.2% annual chance flood hazard (shaded X) (about 56% 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: $2,896,000 – $3,686,000 · 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)0.16 mi NW
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)0.12 mi NW
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)0.11 mi SW
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)0.33 mi NW
Active in "Issued" for 12.8 yr (first record Feb 12, 2014) with no new permit activity recorded in 12.3 yr.
Entity-resolved builders & contractors in ½ mile: Dave Mason Bld (1 on parcel, 1 in ½ mi · Remodel / interior alteration); All Bay Solar Construction (1 on parcel, 1 in ½ mi · Solar / battery storage); Tesla Energy Operations (1 on parcel, 1 in ½ mi · Other); Owner Builder (15 in ½ mi · Remodel / interior alteration); Owner (11 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (3 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B47662 | Other | Issued | Iss. Jul 28, 2026 | $7,000 | — |
| B28100 | Solar / battery storage | Issued | Iss. Dec 15, 2021 | $18,000 | installing a new roof mounted 7.56kw solar system (18)420W AC Modules |
| 169261 | Remodel / interior alteration | Issued | Iss. Sep 2, 2021 | $300,000 | Kitchen & 2 Bath Rmdl; Fireplace Insert; Sunroom Glass; Wndw/Drs; Siding; Skylites,Deck Railings |