136 Blackstone Dr
San Rafael 94903 · Marinwood · Unincorporated Marin · Coordinates: 38.03461, -122.53847
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 $1,280,000 ($1,126,000–$1,434,000).
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
- ✓ 3 documented municipal building permits on file
On-parcel permit history is indexed through Mar 18, 2021, 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: 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)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: 125 new homes (0.3 mi NW, entitled). 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 (~$15,170/yr at $1,280,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,264/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:
- 136 BLACKSTONE DR
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: minimal flood hazard (all of the lot) · FIRM panel 06041C0291D, effective May 4, 2009
- CGS Alquist-Priolo Earthquake Fault Zone
- Not in an Alquist-Priolo Earthquake Fault Zone
Surrounding Rent & Value Benchmarks (Public Records)
Range: $1,126,000 – $1,434,000 · 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
Nearby Activity (½ mile radius, since November 2024)
6 active or recent development projects (129 housing units across completed, permitted, and pipeline stages) and 424 total building permits recorded within ½ mile.
- New construction12 permits
- Adds housing (ADU)4 permits (4 units)
- Demolition2 permits
- Additions & renovations13 permits
- Building systems327 permits
- Repairs32 permits
- Other34 permits
Developments Deserving Closer Investigation & Active Area Builders
- 125 new homes (Entitled)0.3 mi NW
In "Entitled" for 23 mo (since Dec 6, 2024), exceeding the 292d median and 313d 90th percentile for new multifamily / condos / mixed-use permits in Unincorporated Marin (n=21). High-impact scale (125 housing units, 124 deed-restricted affordable across 0 permits).
- New commercial building at 200 Marinwood Ave (Applied)0.12 mi W
Active in "Applied" for 3.9 yr (first record Dec 14, 2022) with no new permit activity recorded in 3.9 yr. High-impact scale ($35,000,000 declared valuation across 2 permits).
- Accessory dwelling unit at 2558 Heatherstone Dr (Applied)0.24 mi NW
In "Applied" for 5.5 yr (since Apr 29, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- Demolition at 187 Marinwood Ave (Issued)0.12 mi SW
Active in "Issued" for 4.5 yr (first record May 13, 2022) with no new permit activity recorded in 4.5 yr.
Entity-resolved builders & contractors in ½ mile: Maap (1 on parcel, 1 in ½ mi · Electrical / panel); Bay Demo (1 on parcel, 1 in ½ mi · Demolition); Telford Electric (1 on parcel, 1 in ½ mi · EV charger); Owner Builder (39 in ½ mi · Remodel / interior alteration); Owner (22 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (3 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B25199 | Electrical / panel | Issued | Iss. Mar 18, 2021 | $25,096 | Replace 12 windows & one 3-panel PD in-kind with white vinyl & 1 entry door size-for-size — Non-structural Door/Window R… |
| B24964 | EV charger | Issued | Iss. Feb 24, 2021 | $1,000 | 60 amp Electric Vehicle Charger Circuit — EV Charging Station; With Electronic Inspection |
| 162567 | Demolition | Issued | Iss. Sep 9, 2019 | $5,500 | Pool Demo |