921 E Blithedale Ave
Mill Valley 94941 · Alto · Unincorporated Marin · Coordinates: 37.90385, -122.51779
Executive Verdict · Public-Records Synthesis
Zoned RMP-40 in Unincorporated Marin with likely ministerial ADU eligibility and mapped FEMA AO flood due diligence; benchmark value $2,111,000 ($1,858,000–$2,364,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone RMP-40 allows residential use qualifying for ministerial ADU review under state law (8 ADU permits permitted within ¼ mile in 36 months).
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ 4 documented municipal building permits on file
On-parcel permit history is indexed through Nov 11, 2024, 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
- ! FEMA Special Flood Hazard Area (AO, about 2% of the lot of lot)
Zone AO: 1% annual chance flood (Special Flood Hazard Area) overlaps this parcel. Expect mandatory flood insurance for federally backed loans and floodplain elevation/mitigation rules for new units or SB 9 applications.
Source: FEMA National Flood Hazard Layer (parcel polygon)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: New home at 55 Thomas Dr (0.33 mi NE, 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 (~$24,727/yr at $2,111,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,061/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:
- 7,579 sq ft (0.17 ac)
- Assessor use:
- Multiple-Resid. - Improved
- Addresses on lot:
- 921 E BLITHEDALE AVE
Zoning & Land Use
RMP-40 — Residential Multiple Planned (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned RMP-40 (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-40 (multifamily residential), not a single-family residential zone.
- SB 9: split into two lotsUnlikely
Zoned RMP-40 (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 AO: 1% annual chance flood (Special Flood Hazard Area) (about 2% of the lot); Zone X: minimal flood hazard (about 98% of the lot) · FIRM panel 06041C0469F, 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: $1,858,000 – $2,364,000 · 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 55 Thomas Dr (Applied)0.33 mi NE
In "Applied" for 6.2 yr (since Sep 1, 2020), 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, $1,000,000 declared valuation across 1 permit).
- Accessory dwelling unit at 55 Plaza Dr (adu 55a) (Issued)190 ft N
Active in "Issued" for 2.6 yr (first record Apr 17, 2024) with no new permit activity recorded in 19 mo. High-impact scale (1 housing unit, $790,000 declared valuation across 1 permit).
- New home at 30 Shell Rd (Issued)0.18 mi N
Active in "Issued" for 2.4 yr (first record Jul 5, 2024) with no new permit activity recorded in 22 mo. High-impact scale (1 housing unit, $2,800,000 declared valuation across 1 permit).
- New home at 55 S Knoll Rd (Issued)0.41 mi SE
Active in "Issued" for 11.9 yr (first record Dec 22, 2014) with no new permit activity recorded in 11.4 yr. High-impact scale (1 housing unit, $750,000 declared valuation across 1 permit).
Entity-resolved builders & contractors in ½ mile: Anderton Construction (2 on parcel, 2 in ½ mi · General repair); Black Diamond Roofing (1 on parcel, 1 in ½ mi · Roof replacement); Hulbert Heating Air Conditioning (1 on parcel, 1 in ½ mi · HVAC / heat pump); Owner Builder (41 in ½ mi · Remodel / interior alteration); Owner (24 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (4 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B40143 | Roof replacement | Issued | Iss. Nov 11, 2024 | $65,400 | Re-roof: Tear off existing roof material, install new 50 MIL PVC — ReRoofing; With Electronic Inspection |
| 151810 | HVAC / heat pump | Issued | Iss. May 2, 2016 | $2,500 | Repl Furnace***Expired |
| 149386 | General repair | Issued | Iss. Oct 13, 2015 | $10,000 | Repairs To 2nd Fl Balconies T.D. 9/2/15 ***Expired |
| 142186 | Other | Issued | Iss. Apr 9, 2014 | $1,500 | Repair Balcony Joists - Express |