57 Plaza Dr
Mill Valley 94941 · Alto · Unincorporated Marin · Coordinates: 37.90440, -122.51816
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 $2,389,000 ($2,102,000–$2,676,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone RA-B2 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
- ✓ Documented permitted upgrades (+$215,204 contributory est.)
Public building records show issued construction/renovation work on this parcel (2 total permits, latest Jan 14, 2022).
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)
- ! 5 slow or stalled nearby projects within ½ mile
Closest lead: New home at 55 Thomas Dr (0.34 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 (~$27,924/yr at $2,389,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,327/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:
- 11,108 sq ft (0.26 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 57 PLAZA DR; 59 PLAZA DR
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: $2,102,000 – $2,676,000 · 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 November 2024)
10 active or recent development projects (10 housing units across completed, permitted, and pipeline stages) and 183 total building permits recorded within ½ mile.
- New construction3 permits (1 units)
- Adds housing (ADU)7 permits (7 units)
- Demolition2 permits
- Additions & renovations26 permits
- Building systems125 permits
- Repairs2 permits
- Other18 permits
Developments Deserving Closer Investigation & Active Area Builders
- New home at 55 Thomas Dr (Applied)0.34 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).
- Accessory dwelling unit at 55 Plaza Dr (adu 55a) (Issued)70 ft E
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).
- New home at 30 Shell Rd (Issued)0.14 mi 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 59 Plaza Dr (Finaled / completed)On this parcel
High-impact scale (1 housing unit, $800,000 declared valuation across 1 permit).
Entity-resolved builders & contractors in ½ mile: Hildebrand Renovation (1 on parcel, 1 in ½ mi · Accessory dwelling unit (new or conversion)); Solarcraft Services (1 on parcel, 1 in ½ mi · Solar / battery storage); Owner Builder (39 in ½ mi · Remodel / interior alteration); Owner (22 in ½ mi · Remodel / interior alteration); Drosihn Construction (7 in ½ mi · New single-family home).
Permit & Project History on This Parcel (2 permits, 1 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B28377 | Solar / battery storage | Issued | Iss. Jan 14, 2022 | $19,058 | (N) FLUSH MOUNTED 3.80 kW PV SYSTEM W/ GRID TIED MICROINVERTERS |
| 168248 | Accessory dwelling unit (new or conversion) | Issued | Iss. May 24, 2021 | $800,000 | Demo/Rebld Single Fam Home W/Attached Adu |
State HCD Housing Element APR records on this parcel: 4 entries (report years 2021, 2022).