331 Jean St
Mill Valley 94941 · Tamalpais · Unincorporated Marin · Coordinates: 37.87828, -122.52975
Executive Verdict · Public-Records Synthesis
Zoned R1 in Unincorporated Marin with likely ministerial ADU eligibility and mapped FEMA AH flood due diligence; benchmark value $2,123,000 ($1,868,000–$2,378,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone R1 allows residential use qualifying for ministerial ADU review under state law (9 ADU permits permitted within ¼ mile in 36 months).
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ 9 documented municipal building permits on file
On-parcel permit history is indexed through Aug 3, 2026, letting you verify roof, HVAC, electrical, or structural work against seller disclosures.
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
- ✓ Above-average reinvestment in Tamalpais
50 substantial renovation & housing permits over 24 months (20.5 per 1,000 parcels vs. 16.3 citywide baseline) (#3 of 22 neighborhoods).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (Tamalpais)
Watchouts & Due Diligence
- ! FEMA Special Flood Hazard Area (AH, all of the lot of lot)
Zone AH: 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 334 Dolan Ave (0.19 mi N, 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 (~$24,865/yr at $2,123,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,072/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:
- 8,364 sq ft (0.19 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 331 JEAN ST
Zoning & Land Use
R1 — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotPossible, with conditions
Zoned R1, a single-family residential zone. FEMA Special Flood Hazard Area (Zone AH) covers all 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 R1, a single-family residential zone. The lot is 8,364 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 AH) covers all 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 AH: 1% annual chance flood (Special Flood Hazard Area) (all of the lot) · FIRM panel 06041C0469F, 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: $1,868,000 – $2,378,000 · Status: Off market
HUD Small Area FMR (ZIP 94941) · FY 2026
Studio $2,730 · 1BR $3,270 · 2BR $3,960 · 3BR $5,060 · 4BR $5,240
Developments Deserving Closer Investigation & Active Area Builders
- New home at 334 Dolan Ave (Issued)0.19 mi N
Active in "Issued" for 8.2 yr (first record Sep 5, 2018) with no new permit activity recorded in 8 yr. High-impact scale (1 housing unit, $759,000 declared valuation across 1 permit).
- Accessory dwelling unit at 403 Marin Ave (adu 403a) (Issued)0.33 mi W
Active in "Issued" for 2.9 yr (first record Dec 21, 2023) with no new permit activity recorded in 19 mo. High-impact scale (1 housing unit, $1,000,000 declared valuation across 1 permit).
- New home at 407 Spruce St (Issued)0.34 mi W
Active in "Issued" for 7.7 yr (first record Mar 14, 2019) with no new permit activity recorded in 7.5 yr. High-impact scale (1 housing unit, $750,000 declared valuation across 1 permit).
- New home at 535 Tennessee Valley Rd (adu 531) (Issued)0.46 mi SE
Active in "Issued" for 6 yr (first record Oct 29, 2020) with no new permit activity recorded in 4 yr. High-impact scale (1 housing unit, $800,000 declared valuation across 1 permit).
Entity-resolved builders & contractors in ½ mile: Peter Levi Plumbing (3 on parcel, 3 in ½ mi · Plumbing / water heater / sewer); De Mello Roofing (2 on parcel, 2 in ½ mi · Roof replacement); J And J Electric (1 on parcel, 1 in ½ mi · Other); Aaero Heating And Sheet Metal (1 on parcel, 1 in ½ mi · HVAC / heat pump); Golden Gate Enterprises (1 on parcel, 1 in ½ mi · General repair).
Permit & Project History on This Parcel (9 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B47720 | Plumbing / water heater / sewer | Issued | Iss. Aug 3, 2026 | $15,000 | Replace Plumbing Fixtures(s) |
| B43344 | Plumbing / water heater / sewer | Issued | Iss. Aug 5, 2025 | $5,000 | Remove & replace 50 gallon water heater like for like. — Replace Plumbing Fixtures(s) |
| B36328 | Other | Issued | Iss. Dec 5, 2023 | $18,833 | Provide and install 16kW Generac generator, 100A disco, and 100A ATS. |
| B28672 | Plumbing / water heater / sewer | Issued | Iss. Feb 9, 2022 | $12,000 | UNDER HOME DRAIN RE PIPE — Replace Plumbing Fixtures(s) |
| 160346 | General repair | Issued | Iss. Dec 17, 2018 |