547 Northern Ave
Mill Valley 94941 · Tamalpais · Unincorporated Marin · Coordinates: 37.88151, -122.54268
Executive Verdict · Public-Records Synthesis
Zoned RA-B2 in Unincorporated Marin with likely ministerial ADU eligibility and mapped CAL FIRE moderate fire hazard severity zone (local responsibility area) due diligence; benchmark value $2,204,000 ($1,940,000–$2,468,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone RA-B2 allows residential use qualifying for ministerial ADU review under state law (2 ADU permits permitted within ¼ mile in 36 months).
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ Documented permitted upgrades (+$12,246 contributory est.)
Public building records show issued construction/renovation work on this parcel (4 total permits, latest Dec 10, 2025).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
- ✓ Above-average reinvestment in Tamalpais
50 substantial renovation & housing permits over 24 months (20.5 per 1,000 parcels vs. 16.4 citywide baseline) (#3 of 22 neighborhoods).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (Tamalpais)
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 Moderate 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)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: Accessory dwelling unit at 875 Marin Dr (0.48 mi S, 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 (~$25,796/yr at $2,204,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,150/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:
- 12,632 sq ft (0.29 ac)
- Assessor use:
- Multiple-Resid. - Improved
- Addresses on lot:
- 547 NORTHERN AVE
Zoning & Land Use
RA-B2 — Residential Agriculture (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned RA-B2 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotCan't tell
Zoned RA-B2 (single-family residential): we can't tell whether it counts as a single-family zone for SB 9. Residential agriculture, estate and restricted: large-lot residential; confirm SB 9 with the county.
- SB 9: split into two lotsCan't tell
Zoned RA-B2 (single-family residential): we can't tell whether it counts as a single-family zone for SB 9. Residential agriculture, estate and restricted: large-lot residential; confirm SB 9 with the county.
Mapped Hazard Zones on This Lot
- CAL FIRE Fire Hazard Severity Zone
- Moderate 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 06041C0468F, 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: $1,940,000 – $2,468,000 · 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 875 Marin Dr (Applied)0.48 mi S
In "Applied" for 2.6 yr (since Apr 11, 2024), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121). Record changed to "updated" in snapshot Nov 4, 2026.
- New home at 560 Alta Way (Applied)0.3 mi N
In "Applied" for 3.3 yr (since Aug 10, 2023), 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, $975,000 declared valuation across 1 permit).
- New home at 731 Bay Rd (Issued)0.22 mi SE
Active in "Issued" for 18 mo (first record May 12, 2025) with no new permit activity recorded in 15 mo. High-impact scale (1 housing unit, $955,000 declared valuation across 1 permit).
- New home at 510 Browning Ct (Issued)0.26 mi NE
Active in "Issued" for 10.2 yr (first record Aug 15, 2016) with no new permit activity recorded in 9.9 yr. High-impact scale (1 housing unit, $900,000 declared valuation across 1 permit).
Entity-resolved builders & contractors in ½ mile: Solarcraft Services (2 on parcel, 2 in ½ mi · Solar / battery storage); Allbay Roofing (1 on parcel, 1 in ½ mi · Roof replacement); Red Mountain Heating And Air (1 on parcel, 1 in ½ mi · Other); Owner Builder (74 in ½ mi · Remodel / interior alteration); Owner (37 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (4 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B45112 | Other | Issued | Iss. Dec 10, 2025 | $8,000 | Like for like replacing gas heater inside the garage. — Replace Mechanical Appliance |
| B36066 | Roof replacement | Issued | Iss. Nov 13, 2023 | $10,400 | Remove all composition shingles on one side only • Apply 30lb felt underlayment • Install 1 ply base sheet • Install 1 p… |
| 156771 | Solar / battery storage | Issued | Iss. Oct 17, 2017 | $4,233 | Thermal System Express |
| 156321 | Solar / battery storage | Issued | Iss. Aug 22, 2017 | $24,744 | 4.81kw Roof Mount Photovoltaic -Express |