42 De Silva Island Dr
Mill Valley 94941 · Strawberry · Unincorporated Marin · Coordinates: 37.88637, -122.51551
Executive Verdict · Public-Records Synthesis
Zoned RMP-1.5-BFC in Unincorporated Marin with likely ministerial ADU eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $2,127,000 ($1,872,000–$2,382,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone RMP-1.5-BFC allows residential use qualifying for ministerial ADU review under state law.
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ 3 documented municipal building permits on file
On-parcel permit history is indexed through Apr 16, 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 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)
- ! 3 slow or stalled nearby projects within ½ mile
Closest lead: Accessory dwelling unit at 25 Vista Del Sol (0.46 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 (~$24,911/yr at $2,127,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,076/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:
- 261 sq ft (0.01 ac)
- Assessor use:
- Single Family Attached
- Addresses on lot:
- 42 DE SILVA ISLAND DR
Zoning & Land Use
RMP-1.5-BFC — Residential Multiple Planned (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned RMP-1.5-BFC (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-1.5-BFC (multifamily residential), not a single-family residential zone.
- SB 9: split into two lotsUnlikely
Zoned RMP-1.5-BFC (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 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: $1,872,000 – $2,382,000 · 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 25 Vista Del Sol (Applied)0.46 mi N
In "Applied" for 2.1 yr (since Oct 11, 2024), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- Demolition at 160 Shoreline Hwy - (Issued)0.38 mi SW
Active in "Issued" for 6.7 yr (first record Feb 19, 2020) with no new permit activity recorded in 6.7 yr.
- New commercial building at 574 Redwood Hwy Frontage Rd Formerly (Issued)0.42 mi N
Active in "Issued" for 11.4 yr (first record Jun 15, 2015) with no new permit activity recorded in 11.1 yr.
- New home at 156 Shoreline Hwy (Issued)0.49 mi SW
High-impact scale ($2,059,500 declared valuation across 1 permit).
Entity-resolved builders & contractors in ½ mile: Ernest Ongaro And Sons (1 on parcel, 1 in ½ mi · HVAC / heat pump); Towery Electric (1 on parcel, 1 in ½ mi · Electrical / panel); Jemico (1 on parcel, 1 in ½ mi · Windows / doors / siding); Owner Builder (5 in ½ mi · Remodel / interior alteration); Icon General Contractors (4 in ½ mi · Commercial tenant improvement).
Permit & Project History on This Parcel (3 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B46519 | Windows / doors / siding | Issued | Iss. Apr 16, 2026 | $3,345 | Non-structural Door/Window Replacement |
| B34535 | HVAC / heat pump | Issued | Iss. Jul 3, 2023 | $17,100 | Replace failed furnace, AC, coil and ducting with new furnace, AC, coil and ducting - ducting located in crawlspace — Re… |
| B32623 | Electrical / panel | Issued | Iss. Feb 15, 2023 | $8,000 | Replace kitchen lighting. Replace dimmers. Add 20 amp circuit for kitchen. Blank off old warning drawer circuit. — New C… |