18 Ninestone Ct
San Rafael 94903 · Marinwood · Unincorporated Marin · Coordinates: 38.03561, -122.54713
Executive Verdict · Public-Records Synthesis
Zoned R1-B4 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 $1,413,000 ($1,243,000–$1,583,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1-B4 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 70,654 sq ft lot. Local precedent is active with 1 ADU permit within ¼ mile over the last 36 months.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ Documented permitted upgrades (+$14,730 contributory est.)
Public building records show issued construction/renovation work on this parcel (11 total permits, latest Oct 31, 2024).
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) (about 99% 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)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: 125 new homes (0.36 mi NE, entitled). 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 (~$16,700/yr at $1,413,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,392/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:
- 70,654 sq ft (1.62 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 18 NINESTONE CT
Zoning & Land Use
R1-B4 — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1-B4 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1-B4, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1-B4, a single-family residential zone. The lot is 70,654 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) (about 99% of the lot, map Apr 1, 2024)
- FEMA National Flood Hazard Layer
- Zone X: minimal flood hazard (all of the lot) · FIRM panel 06041C0291D, 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: $1,243,000 – $1,583,000 · Status: Off market
HUD Small Area FMR (ZIP 94903) · FY 2026
Studio $2,880 · 1BR $3,450 · 2BR $4,180 · 3BR $5,340 · 4BR $5,530
Developments Deserving Closer Investigation & Active Area Builders
- 125 new homes (Entitled)0.36 mi NE
In "Entitled" for 23 mo (since Dec 6, 2024), exceeding the 292d median and 313d 90th percentile for new multifamily / condos / mixed-use permits in Unincorporated Marin (n=21). High-impact scale (125 housing units, 124 deed-restricted affordable across 0 permits).
- New commercial building at 200 Marinwood Ave (Applied)0.37 mi E
Active in "Applied" for 3.9 yr (first record Dec 14, 2022) with no new permit activity recorded in 3.9 yr. High-impact scale ($35,000,000 declared valuation across 2 permits).
- Accessory dwelling unit at 2558 Heatherstone Dr (Applied)0.26 mi E
In "Applied" for 5.5 yr (since Apr 29, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- Accessory dwelling unit at 437 Pinewood Dr (Issued)0.23 mi S
Active in "Issued" for 10.1 yr (first record Oct 17, 2016) with no new permit activity recorded in 9.7 yr.
Entity-resolved builders & contractors in ½ mile: Tesla Energy Operations (3 on parcel, 3 in ½ mi · Electrical / panel); Peter Levi Plumbing (2 on parcel, 2 in ½ mi · HVAC / heat pump); Northwest Exteriors (1 on parcel, 1 in ½ mi · Windows / doors / siding); Solarcity (1 on parcel, 1 in ½ mi · Solar / battery storage); Jemico (1 on parcel, 1 in ½ mi · Windows / doors / siding).
Permit & Project History on This Parcel (11 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B40030 | Electrical / panel | Issued | Iss. Oct 31, 2024 | $1,500 | Inverter swap, location slightly moved. — Replace Circuits / Outlets |
| B39151 | HVAC / heat pump | Issued | Iss. Aug 19, 2024 | $15,000 | Remove and replace heat pump AC like for like — Replace Mechanical Appliance |
| B38609 | Windows / doors / siding | Issued | Iss. Jul 2, 2024 | $8,915 | Replace 1 entry door. — Non-structural Door/Window Replacement |
| B38124 | Electrical / panel | Issued | Iss. May 21, 2024 | $2,000 | Install main panel upgrade to 225A — Service Upgrade |
| B37804 | Solar / battery storage | Issued | Iss. Apr 24, 2024 |