183 Mark Twain Ave
San Rafael 94903 · Santa Venetia · Unincorporated Marin · Coordinates: 38.00466, -122.52604
Executive Verdict · Public-Records Synthesis
Zoned R1 in Unincorporated Marin with likely ministerial ADU eligibility and mapped FEMA AE flood due diligence; benchmark value $1,227,000 ($1,080,000–$1,374,000).
Upsides & Opportunities
- ✓ Ministerial ADU / JADU pathway likely eligible
Zone R1 allows residential use qualifying for ministerial ADU review under state law (1 ADU permit permitted within ¼ mile in 36 months).
Source: Unincorporated Marin zoning · CA Gov. Code 66314
- ✓ Documented permitted upgrades (+$15,702 contributory est.)
Public building records show issued construction/renovation work on this parcel (4 total permits, latest Apr 3, 2023).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
Watchouts & Due Diligence
- ! FEMA Special Flood Hazard Area (AE, about 14% of the lot of lot)
Zone AE: 1% annual chance flood (Special Flood Hazard Area) overlaps this parcel. Expect mandatory flood insurance for federally backed loans and floodplain elevation/mitigation rules for new units or SB 9 applications.
Source: FEMA National Flood Hazard Layer (parcel polygon)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: New commercial building at 170 N San Pedro Rd (0.39 mi S, 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)
- ! Year 1 Prop 13 tax reset (~$14,561/yr at $1,227,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,213/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:
- 9,583 sq ft (0.22 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 183 MARK TWAIN AVE
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 lotPossible, with conditions
Zoned R1, a single-family residential zone. FEMA Special Flood Hazard Area (Zone AE) covers about 14% of the lot: the project must meet the National Flood Insurance Program floodplain standards, or the lot needs a map revision.
- SB 9: split into two lotsPossible, with conditions
Zoned R1, a single-family residential zone. The lot is 9,583 sq ft by the assessor, room for two lots of at least 1,200 sq ft, each at least 40% of the original. FEMA Special Flood Hazard Area (Zone AE) covers about 14% of the lot: the project must meet the National Flood Insurance Program floodplain standards, or the lot needs a map revision.
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 AE: 1% annual chance flood (Special Flood Hazard Area) (about 14% of the lot); Zone X: 0.2% annual chance flood hazard (shaded X) (about 86% of the lot) · FIRM panel 06041C0294E, 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: $1,080,000 – $1,374,000 · 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
- New commercial building at 170 N San Pedro Rd (Issued)0.39 mi S
Active in "Issued" for 4.9 yr (first record Dec 1, 2021) with no new permit activity recorded in 4.4 yr. High-impact scale ($18,000,000 declared valuation across 1 permit).
- New commercial building at 10 Ave Of The Flags (Issued)0.43 mi W
Active in "Issued" for 5.6 yr (first record Mar 26, 2021) with no new permit activity recorded in 5.5 yr. High-impact scale ($2,000,000 declared valuation across 1 permit).
- New home at 16 Crestview Way (Issued)0.5 mi NE
Active in "Issued" for 2.5 yr (first record May 20, 2024) with no new permit activity recorded in 15 mo. High-impact scale (1 housing unit, $770,000 declared valuation across 1 permit).
- Demolition at 13 Edward Ave (Applied)0.27 mi SE
In "Applied" for 3.8 yr (since Jan 23, 2023), exceeding the 55d median and 261d 90th percentile for demolition permits in Unincorporated Marin (n=130).
Entity-resolved builders & contractors in ½ mile: Safe Step Walk In Tub (1 on parcel, 2 in ½ mi · Remodel / interior alteration); Sunrun Installation Services (1 on parcel, 1 in ½ mi · Solar / battery storage); Sonomarin Solar (1 on parcel, 1 in ½ mi · Electrical / panel); Pete A Knight Costruction (1 on parcel, 1 in ½ mi · Electrical / panel); Owner Builder (41 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (4 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B33259 | Solar / battery storage | Issued | Iss. Apr 3, 2023 | $25,517 | 9600W AC, 34 Panel Roof-Mount PV System |
| 166369 | Electrical / panel | Issued | Iss. Nov 24, 2020 | $19,383 | (52) Generator T.D. 10-28-20 |
| 154411 | Remodel / interior alteration | Issued | Iss. Jan 25, 2017 | $15,900 | Inst Walk-In Tub & Dedicated Circuit For Tub - Express |
| B10948 | Electrical / panel | Issued | Iss. Sep 1, 2016 | $2,000 | electrical panel — Service Upgrade |