57 Castle Rock Ave
Woodacre 94973 · Woodacre · Unincorporated Marin · Coordinates: 38.00534, -122.63365
Executive Verdict · Public-Records Synthesis
Zoned R1-B2-SGV in Unincorporated Marin with likely ADU & SB 9 infill eligibility and mapped CAL FIRE high fire hazard severity zone (state responsibility area) due diligence; benchmark value $1,142,000 ($1,005,000–$1,279,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1-B2-SGV supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 12,284 sq ft lot.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ 2 documented municipal building permits on file
On-parcel permit history is indexed through Apr 9, 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)
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 (State Responsibility Area) (all 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 Apr 1, 2024)
- ! 4 slow or stalled nearby projects within ½ mile
Closest lead: New home at 80 Fire Rd (0.31 mi NE, 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 (~$13,583/yr at $1,142,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,132/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:
- 12,284 sq ft (0.28 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 57 CASTLE ROCK AVE
Zoning & Land Use
R1-B2-SGV — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1-B2-SGV (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1-B2-SGV, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1-B2-SGV, a single-family residential zone. The lot is 12,284 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 06041C0275D, effective May 4, 2009
- CGS Alquist-Priolo Earthquake Fault Zone
- Not in an Alquist-Priolo Earthquake Fault Zone
Surrounding Rent & Value Benchmarks (Public Records)
Range: $1,005,000 – $1,279,000 · Status: Off market
HUD Small Area FMR (ZIP 94973) · FY 2026
Studio $2,080 · 1BR $2,510 · 2BR $3,020 · 3BR $3,860 · 4BR $4,000
Developments Deserving Closer Investigation & Active Area Builders
- New home at 80 Fire Rd (Issued)0.31 mi NE
Active in "Issued" for 4.1 yr (first record Sep 28, 2022) with no new permit activity recorded in 3.5 yr. High-impact scale (1 housing unit, $2,000,000 declared valuation across 1 permit).
- New home at 15 Edgewood Dr (Applied)0.34 mi SW
In "Applied" for 6.1 yr (since Oct 22, 2020), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- New home at 10 Holly Ln (Applied)0.41 mi W
Active in "Applied" for 14 mo (first record Sep 17, 2025) with no new permit activity recorded in 14 mo.
- Demolition at 90 Carson Rd (Issued)0.45 mi NW
Active in "Issued" for 4.8 yr (first record Jan 21, 2022) with no new permit activity recorded in 4.7 yr.
Entity-resolved builders & contractors in ½ mile: Northbay Roofing And Gutters (1 on parcel, 1 in ½ mi · Roof replacement); Ernest Ongaro And Sons (1 on parcel, 1 in ½ mi · Plumbing / water heater / sewer); Owner Builder (9 in ½ mi · New garage / accessory structure); Owner (5 in ½ mi · Demolition); Peters Design Build (1 in ½ mi · New single-family home).
Permit & Project History on This Parcel (2 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B46447 | Plumbing / water heater / sewer | Issued | Iss. Apr 9, 2026 | $2,197 | Replace Plumbing Fixtures(s) |
| B45652 | Roof replacement | Issued | Iss. Jan 27, 2026 | $41,901 | ReRoofing; With Electronic Inspection |