90 Adams Ave
Mill Valley 94941 · Muir Woods Park · Unincorporated Marin · Coordinates: 37.90289, -122.56857
Executive Verdict · Public-Records Synthesis
Zoned R1-B2 in Unincorporated Marin with likely ADU & SB 9 infill eligibility and mapped CAL FIRE high fire hazard severity zone (state responsibility area) due diligence; benchmark value $2,489,000 ($2,190,000–$2,788,000).
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 15,943 sq ft lot.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ Documented permitted upgrades (+$277,200 contributory est.)
Public building records show issued construction/renovation work on this parcel (5 total permits, latest Oct 7, 2026).
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 (State 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 Apr 1, 2024)
- ! Delayed or open permit activity on this parcel
Remodel / interior alteration (168095): Issued after 10 mo (3.5× the 83d median) — slower than 90% of remodel / interior alteration permits in Unincorporated Marin (median 83d, 90th pct 266d, n=1,054).
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: New home at 65 Ridge Ave (0.44 mi SE, 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)
Parcel & Assessor
- Lot size:
- 15,943 sq ft (0.37 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 90 ADAMS AVE
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 15,943 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 (State Responsibility Area) (all of the lot, map Apr 1, 2024)
- FEMA National Flood Hazard Layer
- Zone X: minimal flood hazard (all of the lot) · FIRM panel 06041C0465E, effective August 15, 2017
- CGS Alquist-Priolo Earthquake Fault Zone
- Not in an Alquist-Priolo Earthquake Fault Zone
Surrounding Rent & Value Benchmarks (Public Records)
Range: $2,190,000 – $2,788,000 · 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 65 Ridge Ave (Applied)0.44 mi SE
In "Applied" for 4 yr (since Oct 27, 2022), 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, $3,000,000 declared valuation across 1 permit).
- Remodel / interior alteration (168095) (Issued)On this parcel
Issued after 10 mo (3.5× the 83d median) — slower than 90% of remodel / interior alteration permits in Unincorporated Marin (median 83d, 90th pct 266d, n=1,054).
- Remodel / interior alteration (86035) (Applied)On this parcel
Pending in review for 6.3 yr (27.8× the 83d median) — slower than 90% of remodel / interior alteration permits in Unincorporated Marin (median 83d, 90th pct 266d, n=1,054).
- New home at 526 Panoramic Hwy (Issued)410 ft S
Active in "Issued" for 4.6 yr (first record Apr 21, 2022) with no new permit activity recorded in 2 yr. High-impact scale (1 housing unit, $1,329,450 declared valuation across 2 permits).
Entity-resolved builders & contractors in ½ mile: Owner Builder (1 on parcel, 27 in ½ mi · New garage / accessory structure); Owner (1 on parcel, 10 in ½ mi · Remodel / interior alteration); Foley Built (1 on parcel, 1 in ½ mi · Addition (adds square footage)); Vida Building (2 in ½ mi · Remodel / interior alteration); Oxbow Pool And Landscape Contractors (1 in ½ mi · New garage / accessory structure).
Permit & Project History on This Parcel (5 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| 94558 | Remodel / interior alteration | Applied | App. Oct 7, 2026 | — | Addition To Bedroom, Living, And Suite. Roof Raise And Reconfig. Relocate Stairs, Powder Room, And Fireplace. Related To… |
| 180601 | Addition (adds square footage) | Issued | Iss. Dec 15, 2025 | $350,000 | Addn; Rmdl; Roof Deck; Repl Doors, Wndws, Skylights; New Interior Stair; Remodel Kitc & Bath; 2 New Firepls, Replace Fur… |
| 168095 | Remodel / interior alteration | Issued | Iss. May 10, 2021 | $150,000 | Rmdl Whole House; Repl & Add Decks T.D. 10/7/20 |
| 86035 | Remodel / interior alteration | Applied | App. Jul 16, 2020 | — | Structural Remodel Of Entire House. Replace All Decks |
| 150311 | Plumbing / water heater / sewer |