20 Alta Ave
Lagunitas 94938 · Lagunitas · Unincorporated Marin · Coordinates: 38.01687, -122.70350
Executive Verdict · Public-Records Synthesis
Zoned R1-B3-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 $1,077,000 ($948,000–$1,206,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1-B3-SGV supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 10,019 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 (+$22,880 contributory est.)
Public building records show issued construction/renovation work on this parcel (3 total permits, latest Aug 10, 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)
- ! 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 (320 ft NW, 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 (~$12,836/yr at $1,077,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,070/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:
- 10,019 sq ft (0.23 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 20 ALTA AVE
Zoning & Land Use
R1-B3-SGV — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1-B3-SGV (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1-B3-SGV, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1-B3-SGV, a single-family residential zone. The lot is 10,019 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: $948,000 – $1,206,000 · Status: Off market
HUD Small Area FMR (ZIP 94938) · FY 2026
Studio $2,170 · 1BR $2,610 · 2BR $3,150 · 3BR $4,020 · 4BR $4,200
Developments Deserving Closer Investigation & Active Area Builders
- New home (Entitled)320 ft NW
In "Entitled" for 2.1 yr (since Oct 4, 2024), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- Accessory dwelling unit at 5 Barranca Rd (Applied)0.35 mi N
In "Applied" for 7.8 yr (since Feb 7, 2019), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- New home at 152 Alta Ave (Issued)0.1 mi SW
Active in "Issued" for 19 mo (first record Apr 1, 2025) with no new permit activity recorded in 14 mo.
- Demolition at 138 Rodeo Ave (Issued)0.19 mi SE
Active in "Issued" for 12.8 yr (first record Feb 10, 2014) with no new permit activity recorded in 12.8 yr.
Entity-resolved builders & contractors in ½ mile: Simply Solar (2 on parcel, 2 in ½ mi · Solar / battery storage); John A Young (1 on parcel, 1 in ½ mi · EV charger); Owner Builder (8 in ½ mi · Accessory dwelling unit (new or conversion)); Owner (5 in ½ mi · Addition (adds square footage)); Juan Calmell (1 in ½ mi · New single-family home).
Permit & Project History on This Parcel (3 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B35018 | Solar / battery storage | Issued | Iss. Aug 10, 2023 | $2,000 | ESS INSTALLATION, BATTERY BACKUP, WHOLE HOME BACKUP. |
| B33649 | Solar / battery storage | Issued | Iss. Apr 27, 2023 | $51,855 | 7.6 kW RESIDENTIAL PV SOLAR & ESS INSTALLATION, FLUSH ROOF MOUNT, GRID TIED, BATTERYBACKUP, WHOLE HOME BACKUP. |
| B24250 | EV charger | Issued | Iss. Nov 24, 2020 | $3,101 | 220V EV charger; circuit from main panel to garage — New Circuits / Outlets, EV Charging Station |