403 A Marin Ave
Mill Valley 94941 · Tamalpais · Unincorporated Marin · Coordinates: 37.87781, -122.53578
Parcel & Assessor
- Lot size:
- 18,861 sq ft (0.43 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 403A MARIN AVE; 403 MARIN AVE
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 lotLikely eligible
Zoned R1, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1, a single-family residential zone. The lot is 18,861 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
- High Fire Hazard Severity Zone (State Responsibility Area) (all of the lot, map Apr 1, 2024)
- 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: $2,206,000 – $2,808,000 · 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
Nearby Activity (½ mile radius, since October 2024)
25 active or recent development projects (23 housing units across completed, permitted, and pipeline stages) and 580 total building permits recorded within ½ mile.
- New construction13 permits (3 units)
- Adds housing (ADU)20 permits (20 units)
- Demolition2 permits
- Additions & renovations42 permits
- Building systems414 permits
- Repairs19 permits
- Other70 permits
Developments Deserving Closer Investigation & Active Area Builders
- Accessory dwelling unit at 403 Marin Ave (adu 403a) (Issued)On this parcel
Active in "Issued" for 2.9 yr (first record Dec 21, 2023) with no new permit activity recorded in 18 mo. High-impact scale (1 housing unit, $1,000,000 declared valuation across 1 permit).
- New home at 469 W Live Oak Dr (aka 461) (Issued)0.24 mi SW
Active in "Issued" for 6 yr (first record Oct 22, 2020) with no new permit activity recorded in 21 mo. High-impact scale (1 housing unit, $980,000 declared valuation across 1 permit).
- New home at 731 Bay Rd (Issued)0.27 mi W
Active in "Issued" for 18 mo (first record May 12, 2025) with no new permit activity recorded in 14 mo. High-impact scale (1 housing unit, $955,000 declared valuation across 1 permit).
- New home at 746 Alta Vista Rd (Issued)0.36 mi W
Active in "Issued" for 3.3 yr (first record Jul 19, 2023) with no new permit activity recorded in 2.2 yr. High-impact scale (1 housing unit, $1,183,700 declared valuation across 2 permits).
Permit & Project History on This Parcel (4 permits, 1 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| 179084 | General repair | Issued | Iss. Apr 18, 2025 | $50,000 | Rear Concrete Ret Walls |
| 179083 | General repair | Issued | Iss. Apr 18, 2025 | $50,000 | Rear Ret Walls |
| 179082 | General repair | Issued | Iss. Apr 18, 2025 | $100,000 | Driveway Ret Walls |
| 179081 | Accessory dwelling unit (new or conversion) | Issued | Iss. Apr 18, 2025 | $1,000,000 | New S F D; Attached A D U; Garage; Decks; Ret Walls |
State HCD Housing Element APR records on this parcel: 4 entries (report years 2023, 2025).