13 Shell Rd
Mill Valley 94941 · Alto · Unincorporated Marin · Coordinates: 37.90667, -122.51629
Parcel & Assessor
- Lot size:
- 10,280 sq ft (0.24 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 13 SHELL RD
Zoning & Land Use
R1-B1 — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1-B1 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1-B1, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1-B1, a single-family residential zone. The lot is 10,280 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 06041C0467F, 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: $1,902,000 – $2,420,000 · 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 30 Shell Rd (Issued)0.13 mi W
Active in "Issued" for 2.3 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)0.18 mi SW
Active in "Issued" for 2.5 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).
- New home at 55 Thomas Dr (Applied)0.23 mi E
Active in "Applied" for 6.2 yr (first record Sep 1, 2020) with no new permit activity recorded in 6.2 yr. High-impact scale (1 housing unit, $1,000,000 declared valuation across 1 permit).
- New home at 55 S Knoll Rd (Issued)0.49 mi SE
Active in "Issued" for 11.9 yr (first record Dec 22, 2014) with no new permit activity recorded in 11.4 yr. High-impact scale (1 housing unit, $750,000 declared valuation across 1 permit).
Permit & Project History on This Parcel (2 permits, 1 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| 93780 | Accessory dwelling unit (new or conversion) | Applied | App. Dec 4, 2025 | $100,000 | Enlarge Kitchen; Convert Shop To A D U; Seismic Work, Elect In Other Areas B W O P |
| 150288 | Electrical / panel | Issued | Iss. Jan 4, 2016 | $1,200 | New 125a Service ***Extended To 1/4/19 |