178 St Thomas Way
Tiburon 94920 · Paradise Cay · Unincorporated Marin · Coordinates: 37.91466, -122.47527
Executive Verdict · Public-Records Synthesis
Zoned RSP-5.8-BFC in Unincorporated Marin with likely ministerial ADU eligibility and mapped FEMA AE flood due diligence; benchmark value $3,174,000 ($2,793,000–$3,555,000).
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 (+$15,840 contributory est.)
Public building records show issued construction/renovation work on this parcel (12 total permits, latest Feb 24, 2025).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
Watchouts & Due Diligence
- ! FEMA Special Flood Hazard Area (AE, about 65% 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)
- ! Delayed or open permit activity on this parcel
Solar / battery storage (91417): Pending in review for 3.2 yr — slower than 90% of solar / battery storage permits in Unincorporated Marin (median 0d, 90th pct 2d, n=2,977).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (review-time benchmark)
- ! 3 slow or stalled nearby projects within ½ mile
Closest lead: New home at 149 Jamaica St (0.19 mi S, 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 (~$36,951/yr at $3,174,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$3,079/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:
- 12,458 sq ft (0.29 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 178 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 AE) covers about 65% 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 12,458 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 65% 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 AE: 1% annual chance flood (Special Flood Hazard Area) (about 65% of the lot); Zone X: 0.2% annual chance flood hazard (shaded X) (about 35% 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: $2,793,000 – $3,555,000 · 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
- Solar / battery storage (91417) (Applied)On this parcel
Pending in review for 3.2 yr — slower than 90% of solar / battery storage permits in Unincorporated Marin (median 0d, 90th pct 2d, n=2,977).
- Addition (adds square footage) (88061) (Applied)On this parcel
Pending in review for 5.5 yr (12.7× the 160d median) — slower than 90% of addition (adds square footage) permits in Unincorporated Marin (median 160d, 90th pct 440d, n=316).
- Windows / doors / siding (143064) (Issued)On this parcel
Issued after 2 mo — slower than 90% of windows / doors / siding permits in Unincorporated Marin (median 0d, 90th pct 5d, n=1,476).
- New home at 149 Jamaica St (Issued)0.19 mi S
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).
Entity-resolved builders & contractors in ½ mile: Ernest Ongaro And Sons (4 on parcel, 4 in ½ mi · Electrical / panel); Javier Magana Construction Services (2 on parcel, 3 in ½ mi · New garage / accessory structure); Arruda Construction (1 on parcel, 1 in ½ mi · Addition (adds square footage)); Suns Free Solar (1 on parcel, 1 in ½ mi · Solar / battery storage); De Mello 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 |
|---|---|---|---|---|---|
| B41362 | Roof replacement | Issued | Iss. Feb 24, 2025 | $21,530 | TEAR OFF EXISTING ROOF INSTALL COMPOSITION SHINGLE ROOF CLASS A — ReRoofing |
| B37661 | HVAC / heat pump | Issued | Iss. Apr 15, 2024 | $5,800 | Replace failed furnace with new furnace — Replace Mechanical Appliance |
| B35175 | Solar / battery storage | Issued | Iss. Aug 24, 2023 | $66,548 | 8.61 Solar PV on garage roof and (3) Tesla PowerWall2 ESS on side of garage adjacent to MSP |
| 91417 | Solar / battery storage | Applied | App. Aug 14, 2023 | $66,580 | 8.61kw Rooftop Photovoltaic System On Garge & Energy Storage System |
| B32707 | Electrical / panel | Issued |