313 Richardson Dr
Mill Valley 94941 · Strawberry · Unincorporated Marin · Coordinates: 37.89114, -122.50744
Executive Verdict · Public-Records Synthesis
Zoned R1-B2 in Unincorporated Marin with likely ADU & SB 9 infill eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $2,271,000 ($1,998,000–$2,544,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1-B2 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 11,718 sq ft lot. Local precedent is active with 1 ADU permit within ¼ mile over the last 36 months.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ Documented permitted upgrades (+$29,700 contributory est.)
Public building records show issued construction/renovation work on this parcel (2 total permits, latest Oct 23, 2025).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
- ✓ Above-average reinvestment in Strawberry
43 substantial renovation & housing permits over 24 months (28.4 per 1,000 parcels vs. 16.4 citywide baseline) (#1 of 22 neighborhoods).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (Strawberry)
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: New home at 218 Meda Ln (0.11 mi N, 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 (~$26,567/yr at $2,271,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,214/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:
- 11,718 sq ft (0.27 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 313 RICHARDSON DR
Zoning & Land Use
R1-B2 — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1-B2 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1-B2, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1-B2, a single-family residential zone. The lot is 11,718 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
- 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 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: $1,998,000 – $2,544,000 · 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 218 Meda Ln (Applied)0.11 mi N
In "Applied" for 6.5 yr (since Apr 30, 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, $850,000 declared valuation across 1 permit).
- New home at 82 Vista Del Sol (Issued)0.34 mi N
Active in "Issued" for 12.3 yr (first record Aug 7, 2014) with no new permit activity recorded in 12.1 yr. High-impact scale (1 housing unit, $1,000,000 declared valuation across 1 permit).
- New home at 153 Richardson Dr (adu 153a) (Issued)0.45 mi N
Active in "Issued" for 3.4 yr (first record Jun 5, 2023) with no new permit activity recorded in 16 mo. High-impact scale (1 housing unit, $1,493,000 declared valuation across 1 permit).
- New commercial building at 118 E Strawberry Dr (Applied)0.48 mi N
Active in "Applied" for 8.1 yr (first record Oct 3, 2018) with no new permit activity recorded in 8.1 yr. High-impact scale ($1,600,000 declared valuation across 1 permit).
Entity-resolved builders & contractors in ½ mile: Solar Optimum (2 on parcel, 2 in ½ mi · Solar / battery storage); Owner Builder (36 in ½ mi · Remodel / interior alteration); Owner (22 in ½ mi · Remodel / interior alteration); Kerr Construction (6 in ½ mi · Remodel / interior alteration); Lek Enterprises (6 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (2 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B44511 | Solar / battery storage | Issued | Iss. Oct 23, 2025 | $45,000 | Install New Tesla Powerwall 3 with expansion unit, (2 ESS Units at 27 KWH) |
| B39939 | Solar / battery storage | Issued | Iss. Oct 25, 2024 | $30,000 | INSTALL A 10.0 KW. 24 PV MODULES 225A MSP UPGRADE. 1- ESS TESLA BATTERY |