21 Mt Whitney Dr
San Rafael 94903 · Lucas Valley · Unincorporated Marin · Coordinates: 38.03234, -122.57954
Executive Verdict · Public-Records Synthesis
Zoned R1-B-LV in Unincorporated Marin with likely ADU & SB 9 infill eligibility and mapped CAL FIRE high fire hazard severity zone (local responsibility area) due diligence; benchmark value $1,370,000 ($1,206,000–$1,534,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1-B-LV supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 7,318 sq ft lot. Local precedent is active with 2 ADU permits within ¼ mile over the last 36 months.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ 4 documented municipal building permits on file
On-parcel permit history is indexed through Nov 13, 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)
- ! CAL FIRE High Fire Hazard Severity Zone (Local 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 Mar 24, 2025)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: Accessory dwelling unit at 42 Oak Mountain Ct (0.16 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 (~$16,205/yr at $1,370,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,350/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:
- 7,318 sq ft (0.17 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 21 MT WHITNEY DR
Zoning & Land Use
R1-B-LV — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1-B-LV (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1-B-LV, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1-B-LV, a single-family residential zone. The lot is 7,318 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 (Local Responsibility Area) (all of the lot, map Mar 24, 2025)
- FEMA National Flood Hazard Layer
- Zone X: minimal flood hazard (all of the lot) · FIRM panel 06041C0287D, 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: $1,206,000 – $1,534,000 · Status: Off market
HUD Small Area FMR (ZIP 94903) · FY 2026
Studio $2,880 · 1BR $3,450 · 2BR $4,180 · 3BR $5,340 · 4BR $5,530
Developments Deserving Closer Investigation & Active Area Builders
- Accessory dwelling unit at 42 Oak Mountain Ct (Applied)0.16 mi NW
In "Applied" for 5.5 yr (since Apr 30, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- Demolition at 2000 Lucas Valley Rd (Applied)0.23 mi W
In "Applied" for 4.4 yr (since Jun 7, 2022), exceeding the 55d median and 261d 90th percentile for demolition permits in Unincorporated Marin (n=130).
- Accessory dwelling unit at 1 Golden Lily Pl (Applied)0.44 mi W
In "Applied" for 4.8 yr (since Jan 20, 2022), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- New home at 2 Mt Wittenburg Ct (adu 2a) (Issued)0.2 mi SE
Active in "Issued" for 2.5 yr (first record May 29, 2024) with no new permit activity recorded in 21 mo.
Entity-resolved builders & contractors in ½ mile: Owner (2 on parcel, 11 in ½ mi · Remodel / interior alteration); Morris Roofing (1 on parcel, 1 in ½ mi · Roof replacement); I Cannan Electric (1 on parcel, 1 in ½ mi · Electrical / panel); Owner Builder (23 in ½ mi · Remodel / interior alteration); Marin Kitchen Works (5 in ½ mi · Addition (adds square footage)).
Permit & Project History on This Parcel (4 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B49061 | Other | Issued | Iss. Nov 13, 2026 | $25,000 | — |
| B48445 | Electrical / panel | Issued | Iss. Sep 23, 2026 | $1,500 | Service Upgrade |
| B42310 | Other | Issued | Iss. Jun 6, 2025 | $15,000 | Updating two bathrooms. Like for like and no structural changes. |
| B11167 | Roof replacement | Issued | Iss. Oct 10, 2016 | $23,660 | reroof — ReRoofing |