20 A Rosebank Ave
Kentfield 94904 · Kentfield · Unincorporated Marin · Coordinates: 37.95278, -122.54223
Executive Verdict · Public-Records Synthesis
Zoned R1-B1 in Unincorporated Marin with likely ADU & SB 9 infill eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $2,709,000 ($2,384,000–$3,034,000).
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 18,469 sq ft lot. Local precedent is active with 8 ADU permits within ¼ mile over the last 36 months.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ Documented permitted upgrades (+$293,814 contributory est.)
Public building records show issued construction/renovation work on this parcel (8 total permits, latest Apr 11, 2024).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
- ✓ Above-average reinvestment in Kentfield
104 substantial renovation & housing permits over 24 months (41.3 per 1,000 parcels vs. 16.4 citywide baseline) (#7 of 22 neighborhoods).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (Kentfield)
Watchouts & Due Diligence
- ! Mapped flood awareness zone (Zone X: 0.2% annual chance flood hazard (shaded X))
all of the lot of the parcel intersects Zone X: 0.2% annual chance flood hazard (shaded X). Outside mandatory federal SFHA insurance rules, but check local drainage and finished-floor requirements.
Source: FEMA National Flood Hazard Layer (parcel polygon)
- ! Delayed or open permit activity on this parcel
Accessory dwelling unit at 20 Rosebank Ave (aka 20a Rosebank): Active in "Issued" for 2.8 yr (first record Jan 26, 2024) with no new permit activity recorded in 2.6 yr.
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (review-time benchmark)
- ! 5 slow or stalled nearby projects within ½ mile
Closest lead: Accessory dwelling unit at 34 Wolfe Grade (0.37 mi NE, 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 (~$31,604/yr at $2,709,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,634/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:
- 18,469 sq ft (0.42 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 20A ROSEBANK AVE; 20 ROSEBANK AVE
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 18,469 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: 0.2% annual chance flood hazard (shaded X) (all of the lot) · FIRM panel 06041C0458F, 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: $2,384,000 – $3,034,000 · Status: Off market
HUD Small Area FMR (ZIP 94904) · FY 2026
Studio $2,260 · 1BR $2,710 · 2BR $3,280 · 3BR $4,190 · 4BR $4,340
Developments Deserving Closer Investigation & Active Area Builders
- Accessory dwelling unit at 20 Rosebank Ave (aka 20a Rosebank) (Issued)On this parcel
Active in "Issued" for 2.8 yr (first record Jan 26, 2024) with no new permit activity recorded in 2.6 yr.
- Accessory dwelling unit at 34 Wolfe Grade (Applied)0.37 mi NE
In "Applied" for 2.8 yr (since Jan 17, 2024), 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, $750,000 declared valuation across 1 permit).
- New home at 105 Oak Ave (Issued)0.17 mi N
Active in "Issued" for 4.3 yr (first record Jul 15, 2022) with no new permit activity recorded in 14 mo. High-impact scale (1 housing unit, $965,000 declared valuation across 3 permits).
- New home at 49 Laurel Grove Ave (Issued)0.24 mi N
Active in "Issued" for 9.3 yr (first record Jul 18, 2017) with no new permit activity recorded in 9.1 yr. High-impact scale (1 housing unit, $1,200,000 declared valuation across 1 permit).
Entity-resolved builders & contractors in ½ mile: Owner (1 on parcel, 43 in ½ mi · Remodel / interior alteration); Bay City Contractors (3 on parcel, 4 in ½ mi · Remodel / interior alteration); Ernest Ongaro And Sons (1 on parcel, 1 in ½ mi · HVAC / heat pump); C Medina Plumbing (1 on parcel, 1 in ½ mi · Plumbing / water heater / sewer); Lowes Electric (1 on parcel, 1 in ½ mi · Electrical / panel).
Permit & Project History on This Parcel (8 permits, 1 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| 176384 | Accessory dwelling unit (new or conversion) | Issued | Iss. Apr 11, 2024 | $60,000 | Convert (E) Carport To (N) Garage & Build (N) A D U On Top Of Garage; Exterior Stairs T.D. 2-21-24 |
| B33123 | Electrical / panel | Issued | Iss. Mar 24, 2023 | $2,500 | Gas Meter relocation required by PG&E — New Gas Service |
| 173590 | Remodel / interior alteration | Issued | Iss. Mar 16, 2023 | $3,500 | Bath Remodel - Express |
| 171866 | Remodel / interior alteration | Issued | Iss. Jul 8, 2022 | $60,000 |