3 Maxwell Ln
Mill Valley 94941 · Almonte · Unincorporated Marin · Coordinates: 37.89137, -122.53242
Executive Verdict · Public-Records Synthesis
Zoned R1 in Unincorporated Marin with likely ADU & SB 9 infill eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $2,166,000 ($1,906,000–$2,426,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 8,799 sq ft lot. Local precedent is active with 3 ADU permits within ¼ mile over the last 36 months.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ Documented permitted upgrades (+$22,702 contributory est.)
Public building records show issued construction/renovation work on this parcel (6 total permits, latest Apr 21, 2023).
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)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: 2 new homes (0.13 mi N, 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 (~$25,359/yr at $2,166,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,113/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:
- 8,799 sq ft (0.20 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 3 MAXWELL LN
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 8,799 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
- 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 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: $1,906,000 – $2,426,000 · 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
- 2 new homes (Issued)0.13 mi N
Active in "Issued" for 5.7 yr (first record Mar 1, 2021) with no new permit activity recorded in 5.7 yr. High-impact scale (2 housing units, 1 deed-restricted affordable across 0 permits).
- 2 new homes (Issued)0.14 mi N
Active in "Issued" for 5.7 yr (first record Mar 1, 2021) with no new permit activity recorded in 5.7 yr. High-impact scale (2 housing units, 1 deed-restricted affordable across 0 permits).
- New commercial building at 100 Harvard Ave (Issued)0.2 mi S
Active in "Issued" for 23 mo (first record Dec 26, 2024) with no new permit activity recorded in 18 mo. High-impact scale ($6,500,000 declared valuation across 1 permit).
- 9 new homes (Issued)0.23 mi N
Active in "Issued" for 5.4 yr (first record Jun 9, 2021) with no new permit activity recorded in 5.4 yr. High-impact scale (9 housing units across 0 permits).
Entity-resolved builders & contractors in ½ mile: Sun First (2 on parcel, 2 in ½ mi · Solar / battery storage); Ernest Ongaro And Sons (2 on parcel, 2 in ½ mi · Electrical / panel); Massa Construction (1 on parcel, 1 in ½ mi · General repair); Firstpv (1 on parcel, 1 in ½ mi · Solar / battery storage); Owner Builder (85 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (6 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B33558 | Solar / battery storage | Issued | Iss. Apr 21, 2023 | $17,850 | SCOPE 4.000 kW DC ROOF MOUNT SOLAR PV SYSTEM, 10 PANASONIC 400W EVPV400H PV MODULES, 1 SOLAREDGE SE11400H-US INVERTERS. … |
| B31281 | HVAC / heat pump | Issued | Iss. Oct 4, 2022 | $9,900 | Replace furnace with new Air Handler and install Heat Pump - new — Mechanical Appliance, Replace Mechanical Appliance |
| B31053 | Electrical / panel | Issued | Iss. Sep 14, 2022 | $4,000 | Replace 100 amp main panel with 200 amp solar ready main panel. The new panel will be surface mounted in the same locati… |
| 165066 | Solar / battery storage | Issued | Iss. Jul 8, 2020 | $24,000 | Energy Storage System |
| 162828 | General repair |