838 Spring Dr
Mill Valley 94941 · Tamalpais · Unincorporated Marin · Coordinates: 37.87655, -122.54496
Executive Verdict · Public-Records Synthesis
Zoned R1-B1 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 $2,052,000 ($1,806,000–$2,298,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1-B1 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 5,445 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
- ✓ 8 documented municipal building permits on file
On-parcel permit history is indexed through May 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)
- ✓ Above-average reinvestment in Tamalpais
50 substantial renovation & housing permits over 24 months (20.5 per 1,000 parcels vs. 16.4 citywide baseline) (#3 of 22 neighborhoods).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (Tamalpais)
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: Accessory dwelling unit at 875 Marin Dr (0.13 mi S, 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 (~$24,048/yr at $2,052,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,004/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:
- 5,445 sq ft (0.13 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 838 SPRING DR
Zoning & Land Use
R1-B1 — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1-B1 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1-B1, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1-B1, a single-family residential zone. The lot is 5,445 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 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: $1,806,000 – $2,298,000 · 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
- Accessory dwelling unit at 875 Marin Dr (Applied)0.13 mi S
In "Applied" for 2.6 yr (since Apr 11, 2024), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121). Record changed to "updated" in snapshot Nov 4, 2026.
- New home at 812 Spring Dr (Issued)460 ft E
Active in "Issued" for 4.1 yr (first record Sep 19, 2022) with no new permit activity recorded in 3.3 yr. High-impact scale (1 housing unit, $1,006,000 declared valuation across 1 permit).
- New home at 808 Spring Dr (Issued)0.1 mi SE
Active in "Issued" for 4.9 yr (first record Dec 13, 2021) with no new permit activity recorded in 4.7 yr. High-impact scale (1 housing unit, $850,000 declared valuation across 1 permit).
- New home at 746 Alta Vista Rd (Issued)0.16 mi E
Active in "Issued" for 3.3 yr (first record Jul 19, 2023) with no new permit activity recorded in 2.3 yr. High-impact scale (1 housing unit, $1,183,700 declared valuation across 2 permits).
Entity-resolved builders & contractors in ½ mile: Peter Levi Plumbing (3 on parcel, 3 in ½ mi · HVAC / heat pump); Barkley Builders (1 on parcel, 2 in ½ mi · Remodel / interior alteration); Rubin Construction (1 on parcel, 1 in ½ mi · General repair); American Solar (1 on parcel, 1 in ½ mi · Solar / battery storage); Charles Window And Door (1 on parcel, 1 in ½ mi · Windows / doors / siding).
Permit & Project History on This Parcel (8 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B46811 | Plumbing / water heater / sewer | Issued | Iss. May 15, 2026 | $12,000 | Replace Plumbing Fixtures(s) |
| 177942 | Windows / doors / siding | Issued | Iss. Oct 25, 2024 | $40,000 | Window Replacement *Same Plans As T#92500* |
| 177941 | General repair | Issued | Iss. Oct 25, 2024 | $20,000 | Replace Failing Beam @ Garage Ceiling *Same Plans As T#92696* |
| B26039 | HVAC / heat pump | Issued | Iss. Jun 14, 2021 | $6,050 | 80% 66K BTU FAU CHANGE OUT IN BASEMENT WITH 5 RUNS OF DUCTING — Replace Ductwork, Replace Mechanical Appliance |
| B25557 | HVAC / heat pump | Issued | Iss. Apr 22, 2021 |