121 Altena St
San Rafael 94901 · California Park · Unincorporated Marin · Coordinates: 37.95458, -122.50914
Executive Verdict · Public-Records Synthesis
Zoned RMP-12.45 in Unincorporated Marin with likely ministerial ADU eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $1,333,000 ($1,173,000–$1,493,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone RMP-12.45 allows residential use qualifying for ministerial ADU review under state law (3 ADU permits permitted within ¼ mile in 36 months).
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ 3 documented municipal building permits on file
On-parcel permit history is indexed through Sep 15, 2026, letting you verify roof, HVAC, electrical, or structural work against seller disclosures.
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: 79 new homes at 0 Auburn St & Woodland Ave (0.32 mi NW, 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 (~$15,780/yr at $1,333,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,315/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:
- 5,097 sq ft (0.12 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 121 ALTENA ST
Zoning & Land Use
RMP-12.45 — Residential Multiple Planned (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned RMP-12.45 (multifamily residential): state law allows ADUs where homes are allowed. On a multifamily lot the state allowance is different: ADUs in non-living space of the building, plus up to eight detached ADUs.
- SB 9: two homes on the lotUnlikely
Zoned RMP-12.45 (multifamily residential), not a single-family residential zone.
- SB 9: split into two lotsUnlikely
Zoned RMP-12.45 (multifamily residential), not a single-family residential zone.
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 06041C0459F, 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: $1,173,000 – $1,493,000 · Status: Off market
HUD Small Area FMR (ZIP 94901) · FY 2026
Studio $2,150 · 1BR $2,580 · 2BR $3,120 · 3BR $3,990 · 4BR $4,130
Developments Deserving Closer Investigation & Active Area Builders
- 79 new homes at 0 Auburn St & Woodland Ave (Applied)0.32 mi NW
In "Applied" for 23 mo (since Dec 18, 2024), exceeding the 292d median and 313d 90th percentile for new multifamily / condos / mixed-use permits in Unincorporated Marin (n=21). High-impact scale (79 housing units, 16 deed-restricted affordable across 16 permits).
- Demolition at 202 Auburn St (Applied)0.23 mi NW
In "Applied" for 4.2 yr (since Sep 14, 2022), exceeding the 55d median and 261d 90th percentile for demolition permits in Unincorporated Marin (n=130).
- New home (Entitled)0.33 mi W
In "Entitled" for 8.2 yr (since Sep 12, 2018), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- Accessory dwelling unit at 134 Orange St (Applied)0.36 mi NW
In "Applied" for 5.2 yr (since Sep 8, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
Entity-resolved builders & contractors in ½ mile: The Furnace Man (1 on parcel, 1 in ½ mi · Other); S Waters Plumbing (1 on parcel, 1 in ½ mi · Plumbing / water heater / sewer); Sgk Home Solutions (1 on parcel, 1 in ½ mi · Windows / doors / siding); Owner Builder (14 in ½ mi · Remodel / interior alteration); Owner (5 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (3 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B48333 | Other | Issued | Iss. Sep 15, 2026 | $7,500 | Replace Mechanical Appliance |
| B48321 | Plumbing / water heater / sewer | Issued | Iss. Sep 14, 2026 | $3,894 | Replace Plumbing Fixtures(s) |
| 150793 | Windows / doors / siding | Issued | Iss. Feb 16, 2016 | $933 | Repl 2 Wndws In Kind - Must Meet W U I Requirements |