169 Mark Twain Ave
San Rafael 94903 · Santa Venetia · Unincorporated Marin · Coordinates: 38.00405, -122.52759
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 $1,191,000 ($1,048,000–$1,334,000).
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
- ✓ 5 documented municipal building permits on file
On-parcel permit history is indexed through Jun 27, 2024, letting you verify roof, HVAC, electrical, or structural work against seller disclosures.
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))
about 99% 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)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: New commercial building at 10 Ave Of The Flags (0.34 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 (~$14,147/yr at $1,191,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,179/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:
- 169 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) (about 99% 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: $1,048,000 – $1,334,000 · 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 10 Ave Of The Flags (Issued)0.34 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)0.29 mi S
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).
- Demolition at 13 Edward Ave (Applied)0.3 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: Charles Window And Door (1 on parcel, 1 in ½ mi · Windows / doors / siding); Excellence Heating And Air (1 on parcel, 1 in ½ mi · HVAC / heat pump); Zaragoza Plumbing (1 on parcel, 1 in ½ mi · Plumbing / water heater / sewer); Window Factory (1 on parcel, 1 in ½ mi · Windows / doors / siding); Ernest Ongaro And Sons (1 on parcel, 1 in ½ mi · Plumbing / water heater / sewer).
Permit & Project History on This Parcel (5 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B38539 | Plumbing / water heater / sewer | Issued | Iss. Jun 27, 2024 | $1,600 | Replace failed 40 gal WH with new 40 gal WH — Replace Plumbing Fixtures(s) |
| B24603 | HVAC / heat pump | Issued | Iss. Jan 12, 2021 | $5,853 | replace with a 96% efficiency 2 stage furnace — Replace Mechanical Appliance |
| 152277 | Plumbing / water heater / sewer | Issued | Iss. Jun 9, 2016 | $3,500 | Repl Tankless W/40 Gal Water Heater |
| 148636 | Windows / doors / siding | Issued | Iss. Aug 31, 2015 | $10,000 | Enlarge (E) Patio Dr & Close-In Window |
| 148123 | Windows / doors / siding | Issued | Iss. Jul 23, 2015 |