403 Shoreline Hwy
Mill Valley 94941 · Tamalpais · Unincorporated Marin · Coordinates: 37.87938, -122.53550
Executive Verdict · Public-Records Synthesis
Zoned R2 in Unincorporated Marin with likely ministerial ADU eligibility and mapped CAL FIRE high fire hazard severity zone (local responsibility area) due diligence; benchmark value $2,112,000 ($1,859,000–$2,365,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone R2 allows residential use qualifying for ministerial ADU review under state law (5 ADU permits permitted within ¼ mile in 36 months).
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ 4 documented municipal building permits on file
On-parcel permit history is indexed through Sep 2, 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. 16.4 citywide baseline) (#3 of 22 neighborhoods).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (Tamalpais)
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)
- ! CAL FIRE High Fire Hazard Severity Zone (Local Responsibility Area) (about 84% of the lot of lot)
Located in a mapped Fire Hazard Severity Zone. Expect Chapter 7A ignition-resistant building standards, defensible-space inspections, and stricter property insurance underwriting.
Source: CAL FIRE FHSZ (map Mar 24, 2025)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: Accessory dwelling unit at 403 Marin Ave (adu 403a) (510 ft 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 (~$24,738/yr at $2,112,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,062/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:
- 7,797 sq ft (0.18 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 403 SHORELINE HWY
Zoning & Land Use
R2 — Residential Two Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R2 (two-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotCan't tell
Zoned R2 (two-family residential): we can't tell whether it counts as a single-family zone for SB 9. Residential Two Family.
- SB 9: split into two lotsCan't tell
Zoned R2 (two-family residential): we can't tell whether it counts as a single-family zone for SB 9. Residential Two Family.
Mapped Hazard Zones on This Lot
- CAL FIRE Fire Hazard Severity Zone
- High Fire Hazard Severity Zone (Local Responsibility Area) (about 84% of the lot, map Mar 24, 2025); Moderate Fire Hazard Severity Zone (Local Responsibility Area) (about 16% of the lot, map Mar 24, 2025)
- FEMA National Flood Hazard Layer
- Zone X: minimal flood hazard (all of the lot) · FIRM panel 06041C0468F, 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: $1,859,000 – $2,365,000 · 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
- Accessory dwelling unit at 403 Marin Ave (adu 403a) (Issued)510 ft S
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 731 Bay Rd (Issued)0.29 mi W
Active in "Issued" for 18 mo (first record May 12, 2025) with no new permit activity recorded in 15 mo. High-impact scale (1 housing unit, $955,000 declared valuation across 1 permit).
- New home at 469 W Live Oak Dr (aka 461) (Issued)0.32 mi SW
Active in "Issued" for 6.1 yr (first record Oct 22, 2020) with no new permit activity recorded in 22 mo. High-impact scale (1 housing unit, $980,000 declared valuation across 1 permit).
- New home at 746 Alta Vista Rd (Issued)0.41 mi SW
Active in "Issued" for 3.3 yr (first record Jul 19, 2023) with no new permit activity recorded in 2.3 yr. High-impact scale (1 housing unit, $1,183,700 declared valuation across 2 permits).
Entity-resolved builders & contractors in ½ mile: Jemico (1 on parcel, 1 in ½ mi · Windows / doors / siding); Golden Grove Roofing And Construction (1 on parcel, 1 in ½ mi · Roof replacement); Rps Remodeling (1 on parcel, 1 in ½ mi · Windows / doors / siding); Divine Electric (1 on parcel, 1 in ½ mi · Electrical / panel); Owner Builder (102 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (4 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B48196 | Roof replacement | Issued | Iss. Sep 2, 2026 | $23,360 | ReRoofing; With Electronic Inspection |
| B46513 | Electrical / panel | Issued | Iss. Apr 16, 2026 | $4,500 | Replace Circuits / Outlets |
| B38930 | Windows / doors / siding | Issued | Iss. Jul 30, 2024 | $6,500 | Install T 1-11 plywood siding to front bay wall and adjacent right side wall. Also far left side wall. Approx.600 sq.ft … |
| B38491 | Windows / doors / siding | Issued | Iss. Jul 25, 2024 | $25,095 | Replace 4 retrofit windows and 1 retrofit sliding door — Non-structural Door/Window Replacement |