31 Ridge Ave
Mill Valley 94941 · Muir Woods Park · Unincorporated Marin · Coordinates: 37.89891, -122.56697
Executive Verdict · Public-Records Synthesis
Zoned R1-B3 in Unincorporated Marin and mapped CAL FIRE very high fire hazard severity zone (state responsibility area) due diligence; benchmark value $2,301,000 ($2,025,000–$2,577,000).
Upsides & Opportunities
- ✓ Documented permitted upgrades (+$16,000 contributory est.)
Public building records show issued construction/renovation work on this parcel (4 total permits, latest Jul 26, 2017).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
Watchouts & Due Diligence
- ! Mapped flood awareness zone (Zone D: possible but undetermined flood hazard)
all of the lot of the parcel intersects Zone D: possible but undetermined 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 Very 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)
- ! Delayed or open permit activity on this parcel
General repair (154091): Issued after 6 mo (2.2× the 83d median) — above the 75th percentile for general repair permits in Unincorporated Marin (median 83d, 75th pct 181d, n=693).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (review-time benchmark)
- ! 4 slow or stalled nearby projects within ½ mile
Closest lead: New home at 65 Ridge Ave (0.17 mi SE, 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)
Parcel & Assessor
- Lot size:
- 35,632 sq ft (0.82 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 31 RIDGE AVE
Zoning & Land Use
R1-B3 — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADUPossible, with conditions
Zoned R1-B3 (single-family residential): state law allows ADUs where homes are allowed. Very High Fire Hazard Severity Zone covers all of the lot: cities may limit ADUs here for fire safety and evacuation.
- SB 9: two homes on the lotPossible, with conditions
Zoned R1-B3, a single-family residential zone. Very High Fire Hazard Severity Zone (State responsibility area) covers all of the lot: SB 9 requires the project to meet the fire hazard mitigation standards.
- SB 9: split into two lotsPossible, with conditions
Zoned R1-B3, a single-family residential zone. The lot is 35,632 sq ft by the assessor, room for two lots of at least 1,200 sq ft, each at least 40% of the original. Very High Fire Hazard Severity Zone (State responsibility area) covers all of the lot: SB 9 requires the project to meet the fire hazard mitigation standards.
Mapped Hazard Zones on This Lot
- CAL FIRE Fire Hazard Severity Zone
- Very High Fire Hazard Severity Zone (State Responsibility Area) (all of the lot, map Apr 1, 2024)
- FEMA National Flood Hazard Layer
- Zone D: possible but undetermined flood hazard (all of the lot) · FIRM panel 06041C0465E, effective August 15, 2017
- CGS Alquist-Priolo Earthquake Fault Zone
- Not in an Alquist-Priolo Earthquake Fault Zone
Surrounding Rent & Value Benchmarks (Public Records)
Range: $2,025,000 – $2,577,000 · 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 65 Ridge Ave (Applied)0.17 mi SE
In "Applied" for 4 yr (since Oct 27, 2022), 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, $3,000,000 declared valuation across 1 permit).
- New home at 526 Panoramic Hwy (Issued)0.21 mi N
Active in "Issued" for 4.6 yr (first record Apr 21, 2022) with no new permit activity recorded in 2 yr. High-impact scale (1 housing unit, $1,329,450 declared valuation across 2 permits).
- New home at 31 Ridge Ave (formerly 23) (Finaled / completed)On this parcel
High-impact scale (1 housing unit, $1,100,000 declared valuation across 1 permit).
- New home at 49 Ridge Ave (Applied)370 ft SE
In "Applied" for 5.1 yr (since Oct 15, 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: Owner Builder (3 on parcel, 30 in ½ mi · Remodel / interior alteration); Owner (10 in ½ mi · Remodel / interior alteration); Vida Building (2 in ½ mi · Remodel / interior alteration); Soruco Structures (2 in ½ mi · Remodel / interior alteration); D3 Consult Design Build (2 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (4 permits, 1 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| 156087 | Addition (adds square footage) | Issued | Iss. Jul 26, 2017 | $3,000 | Addn To Permit 154090 |
| 154092 | General repair | Issued | Iss. Dec 15, 2016 | $2,000 | Ret Wall # 2 Lower Landscaping |
| 154091 | General repair | Issued | Iss. Dec 15, 2016 | $5,000 | Ret Wall #1 (1 Permit Per J W) Driveway |
| 154090 | New single-family home | Issued | Iss. Dec 15, 2016 | $1,100,000 | S F D; Gar; Decks; Covered Porches Scott 415-307-2253***Extended To 12/15/19 |