157 Mark Twain Ave
San Rafael 94903 · Santa Venetia · Unincorporated Marin · Coordinates: 38.00332, -122.52867
Executive Verdict · Public-Records Synthesis
Zoned R1 in Unincorporated Marin with likely ADU & SB 9 infill eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $1,201,000 ($1,057,000–$1,345,000).
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 7,710 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 (+$9,619 contributory est.)
Public building records show issued construction/renovation work on this parcel (5 total permits, latest Oct 9, 2024).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
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
Remodel / interior alteration (87489): Pending in review for 5.8 yr (25.4× 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)
- ! 5 slow or stalled nearby projects within ½ mile
Closest lead: New commercial building at 10 Ave Of The Flags (0.27 mi W, 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 (~$14,262/yr at $1,201,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,188/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:
- 7,710 sq ft (0.18 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 157 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 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 7,710 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 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: $1,057,000 – $1,345,000 · 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
- Remodel / interior alteration (87489) (Applied)On this parcel
Pending in review for 5.8 yr (25.4× the 83d median) — slower than 90% of remodel / interior alteration permits in Unincorporated Marin (median 83d, 90th pct 266d, n=1,054).
- New commercial building at 10 Ave Of The Flags (Issued)0.27 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 commercial building at 170 N San Pedro Rd (Issued)0.39 mi SE
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).
- Accessory dwelling unit at 15 Roosevelt Ave (Applied)0.27 mi SE
In "Applied" for 4.3 yr (since Jul 13, 2022), 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: John Owens Services (1 on parcel, 1 in ½ mi · HVAC / heat pump); Sunrun Installation Services (1 on parcel, 1 in ½ mi · Solar / battery storage); Ed Electric (1 on parcel, 1 in ½ mi · Electrical / panel); Sun Beam Solar Energy (1 on parcel, 1 in ½ mi · Electrical / panel); Owner Builder (35 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (5 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B39684 | Solar / battery storage | Issued | Iss. Oct 9, 2024 | $23,234 | PV SOLAR 4860W DC, 23000W AC, (12) MODULES, (2) 13.5KWH ESS |
| B24795 | Electrical / panel | Issued | Iss. Feb 3, 2021 | $3,500 | Upgrading Sub panel. currently located inside the wall of kitchen and garage. Adding 8 reset lighting in living room,kit… |
| 87489 | Remodel / interior alteration | Applied | App. Feb 3, 2021 | $100,000 | Remodel Kitchen And Master Bath |
| B24678 | HVAC / heat pump | Issued | Iss. Jan 22, 2021 | $23,515 | Replace furnace, AC and 7 duct runs — Replace Ductwork, Replace Mechanical Appliance |
| B24577 | Electrical / panel | Issued |