9 Maxwell Ln
Mill Valley 94941 · Almonte · Unincorporated Marin · Coordinates: 37.89089, -122.53253
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 $2,324,000 ($2,045,000–$2,603,000).
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 27,443 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 (+$6,854 contributory est.)
Public building records show issued construction/renovation work on this parcel (5 total permits, latest Jun 16, 2026).
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 (0.17 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 (~$27,176/yr at $2,324,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,265/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:
- 27,443 sq ft (0.63 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 9 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 27,443 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: $2,045,000 – $2,603,000 · 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)0.17 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)0.17 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)0.17 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)0.26 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: Owner (2 on parcel, 42 in ½ mi · Remodel / interior alteration); North HVAC Services (2 on parcel, 2 in ½ mi · HVAC / heat pump); Tesla Energy (1 on parcel, 1 in ½ mi · Solar / battery storage); Owner Builder (88 in ½ mi · Remodel / interior alteration); Miette (6 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (5 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B47182 | Other | Issued | Iss. Jun 16, 2026 | $18,675 | Mechanical Appliance |
| B43850 | HVAC / heat pump | Issued | Iss. Sep 11, 2025 | $9,782 | ductless single zone heat pump — Mechanical Appliance |
| B43099 | Windows / doors / siding | Issued | Iss. Jul 14, 2025 | $22,000 | Replace 11 windows and 3 doors, all within existing frames. — Non-structural Door/Window Replacement |
| B41906 | Plumbing / water heater / sewer | Issued | Iss. Apr 4, 2025 | $20,000 | Expanding existing bathroom (78sq ft), and removing another existing bathroom (32 sq ft), total area of work 110 sq ft. … |
| 165988 | Solar / battery storage | Issued |