1019 A Trillium Ln
Mill Valley 94941 · Tamalpais · Unincorporated Marin · Coordinates: 37.88730, -122.54554
Executive Verdict · Public-Records Synthesis
Zoned RSP-2 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 $2,541,000 ($2,236,000–$2,846,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned RSP-2 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 24,568 sq ft lot. Local precedent is active with 6 ADU permits within ¼ mile over the last 36 months.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ Documented permitted upgrades (+$239,200 contributory est.)
Public building records show issued construction/renovation work on this parcel (6 total permits, latest Aug 6, 2025).
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 (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)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: New home at 560 Alta Way (0.3 mi SE, 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 (~$29,672/yr at $2,541,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,473/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:
- 24,568 sq ft (0.56 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 1019A TRILLIUM LN; 1019 TRILLIUM LN
Zoning & Land Use
RSP-2 — Residential Single Family Planned (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned RSP-2 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned RSP-2, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned RSP-2, a single-family residential zone. The lot is 24,568 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: $2,236,000 – $2,846,000 · 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
- New home at 560 Alta Way (Applied)0.3 mi SE
In "Applied" for 3.3 yr (since Aug 10, 2023), 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, $975,000 declared valuation across 1 permit).
- New home at 510 Browning Ct (Issued)0.39 mi SE
Active in "Issued" for 10.2 yr (first record Aug 15, 2016) with no new permit activity recorded in 9.9 yr. High-impact scale (1 housing unit, $900,000 declared valuation across 1 permit).
- New home at 210 Brabo Ter (Issued)0.47 mi NE
Active in "Issued" for 3.1 yr (first record Oct 12, 2023) with no new permit activity recorded in 2.6 yr. High-impact scale (1 housing unit, $850,000 declared valuation across 1 permit).
- New home at 204 Reed St (Issued)0.5 mi NE
Active in "Issued" for 4.3 yr (first record Aug 5, 2022) with no new permit activity recorded in 3.5 yr. High-impact scale (1 housing unit, $950,000 declared valuation across 1 permit).
Entity-resolved builders & contractors in ½ mile: Bellows Plumbing Heating And Air (2 on parcel, 3 in ½ mi · Accessory dwelling unit (new or conversion)); Burton Builders (1 on parcel, 1 in ½ mi · Accessory dwelling unit (new or conversion)); All Exterior Construction (1 on parcel, 1 in ½ mi · Windows / doors / siding); Sonomarin Solar (1 on parcel, 1 in ½ mi · Electrical / panel); Master Roofing (1 on parcel, 1 in ½ mi · Roof replacement).
Permit & Project History on This Parcel (6 permits, 1 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B43366 | Windows / doors / siding | Issued | Iss. Aug 6, 2025 | $55,400 | We will remove the siding on the street facing side of the home, install a 1/2 plywood, and install james hardie lap sid… |
| 176754 | Accessory dwelling unit (new or conversion) | Issued | Iss. May 30, 2024 | $189,210 | C O U Garage To A D U & Storage Legalize (E) Garage Structure |
| B29534 | Plumbing / water heater / sewer | Issued | Iss. Apr 26, 2022 | $1,500 | Replace existing 50 gallon water heater in standing crawl space with new, like for like. — Replace Plumbing Fixtures(s) |
| B29532 | HVAC / heat pump | Issued |