860 Idylberry Rd
San Rafael 94903 · Marinwood · Unincorporated Marin · Coordinates: 38.02866, -122.56143
Executive Verdict · Public-Records Synthesis
Zoned R1 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 $1,339,000 ($1,178,000–$1,500,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 11,979 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 (+$14,400 contributory est.)
Public building records show issued construction/renovation work on this parcel (6 total permits, latest May 28, 2021).
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)
- ! Delayed or open permit activity on this parcel
Accessory dwelling unit at 860 Idylberry Rd: In "Applied" for 5.5 yr (since May 28, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
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: Accessory dwelling unit at 598 Loganberry Dr (adu 598a) (0.41 mi NE, issued). 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:
- 11,979 sq ft (0.28 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 860 IDYLBERRY RD
Zoning & Land Use
R1 — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1, a single-family residential zone. The lot is 11,979 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 06041C0293E, 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: $1,178,000 – $1,500,000 · 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 860 Idylberry Rd (Applied)On this parcel
In "Applied" for 5.5 yr (since May 28, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- Accessory dwelling unit (new or conversion) (88317) (Applied)On this parcel
Pending in review for 5.5 yr (9.8× the 204d median) — slower than 90% of accessory dwelling unit (new or conversion) permits in Unincorporated Marin (median 204d, 90th pct 549d, n=298).
- Accessory dwelling unit at 598 Loganberry Dr (adu 598a) (Issued)0.41 mi NE
Active in "Issued" for 2.2 yr (first record Sep 6, 2024) with no new permit activity recorded in 22 mo. High-impact scale (1 housing unit, $830,000 declared valuation across 1 permit).
- New home (Entitled)0.34 mi W
In "Entitled" for 2.9 yr (since Dec 7, 2023), 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 (1 on parcel, 6 in ½ mi · Remodel / interior alteration); Sonomarin Solar (1 on parcel, 1 in ½ mi · Solar / battery storage); Abril Roofing (1 on parcel, 1 in ½ mi · Roof replacement); Integrity Electric (1 on parcel, 1 in ½ mi · EV charger); No Ark Electric (1 on parcel, 1 in ½ mi · Electrical / panel).
Permit & Project History on This Parcel (6 permits, 1 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| 88317 | Accessory dwelling unit (new or conversion) | Applied | App. May 28, 2021 | $110,000 | Det A D U |
| B25499 | EV charger | Issued | Iss. Apr 21, 2021 | $2,000 | SERVICE UPGRADE TO A 200 AMP MAIN PANEL ELECTRIC VEHICLE STATION — Service Upgrade, EV Charging Station |
| 167177 | Solar / battery storage | Issued | Iss. Feb 17, 2021 | $60,493 | 11.25kw Rooftop Photovoltaic & Energy Storage System |
| 147109 | Plumbing / water heater / sewer | Issued | Iss. May 14, 2015 | $2,500 |