33 Shell Rd
Mill Valley 94941 · Alto · Unincorporated Marin · Coordinates: 37.90594, -122.51869
Executive Verdict · Public-Records Synthesis
Zoned RA-B2 in Unincorporated Marin with likely ministerial ADU eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $2,190,000 ($1,927,000–$2,453,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone RA-B2 allows residential use qualifying for ministerial ADU review under state law (10 ADU permits permitted within ¼ mile in 36 months).
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ 1 documented municipal building permit on file
On-parcel permit history is indexed through Dec 18, 2025, 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)
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 55 Thomas Dr (0.35 mi E, applied). 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 (~$25,635/yr at $2,190,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,136/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:
- 12,240 sq ft (0.28 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 33 SHELL RD
Zoning & Land Use
RA-B2 — Residential Agriculture (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned RA-B2 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotCan't tell
Zoned RA-B2 (single-family residential): we can't tell whether it counts as a single-family zone for SB 9. Residential agriculture, estate and restricted: large-lot residential; confirm SB 9 with the county.
- SB 9: split into two lotsCan't tell
Zoned RA-B2 (single-family residential): we can't tell whether it counts as a single-family zone for SB 9. Residential agriculture, estate and restricted: large-lot residential; confirm SB 9 with the county.
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 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: $1,927,000 – $2,453,000 · 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 55 Thomas Dr (Applied)0.35 mi E
In "Applied" for 6.2 yr (since Sep 1, 2020), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121). High-impact scale (1 housing unit, $1,000,000 declared valuation across 1 permit).
- New home at 30 Shell Rd (Issued)180 ft N
Active in "Issued" for 2.4 yr (first record Jul 5, 2024) with no new permit activity recorded in 22 mo. High-impact scale (1 housing unit, $2,800,000 declared valuation across 1 permit).
- Accessory dwelling unit at 55 Plaza Dr (adu 55a) (Issued)0.12 mi S
Active in "Issued" for 2.6 yr (first record Apr 17, 2024) with no new permit activity recorded in 19 mo. High-impact scale (1 housing unit, $790,000 declared valuation across 1 permit).
- Accessory dwelling unit at 36 Meadow Dr (Applied)300 ft SW
In "Applied" for 6.7 yr (since Feb 20, 2020), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
Entity-resolved builders & contractors in ½ mile: Nationwide Environmental And Construction Services (1 on parcel, 1 in ½ mi · Electrical / panel); Owner Builder (34 in ½ mi · Remodel / interior alteration); Owner (20 in ½ mi · Remodel / interior alteration); Drosihn Construction (6 in ½ mi · New single-family home); Kurt Jehling Construction (4 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (1 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B45214 | Electrical / panel | Issued | Iss. Dec 18, 2025 | $10,312 | Install a 24kW Generac Standby System with ATS. All gas and electrical installation included. Install new 200A load cent… |