280 Shoreline Hwy
Mill Valley 94941 · Almonte · Unincorporated Marin · Coordinates: 37.88134, -122.52670
Executive Verdict · Public-Records Synthesis
Zoned R1-B1 in Unincorporated Marin with likely ADU & SB 9 infill eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $2,038,000 ($1,793,000–$2,283,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1-B1 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 4,661 sq ft lot. Local precedent is active with 8 ADU permits within ¼ mile over the last 36 months.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ 6 documented municipal building permits on file
On-parcel permit history is indexed through Jun 22, 2023, 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)
- ! Delayed or open permit activity on this parcel
Addition (adds square footage) (91238): Pending in review for 3.4 yr (7.8× the 160d median) — slower than 90% of addition (adds square footage) permits in Unincorporated Marin (median 160d, 90th pct 440d, n=316).
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 home at 217 Cleveland Ave (0.27 mi N, 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 (~$23,887/yr at $2,038,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,991/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:
- 4,661 sq ft (0.11 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 280 SHORELINE HWY
Zoning & Land Use
R1-B1 — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1-B1 (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1-B1, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1-B1, a single-family residential zone. The lot is 4,661 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 06041C0469F, 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: $1,793,000 – $2,283,000 · 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
Nearby Activity (½ mile radius, since November 2024)
20 active or recent development projects (18 housing units across completed, permitted, and pipeline stages) and 557 total building permits recorded within ½ mile.
- New construction15 permits (2 units)
- Adds housing (ADU)16 permits (16 units)
- Demolition1 permit
- Additions & renovations42 permits
- Building systems398 permits
- Repairs25 permits
- Other60 permits
Developments Deserving Closer Investigation & Active Area Builders
- Addition (adds square footage) (91238) (Applied)On this parcel
Pending in review for 3.4 yr (7.8× the 160d median) — slower than 90% of addition (adds square footage) permits in Unincorporated Marin (median 160d, 90th pct 440d, n=316).
- New home at 217 Cleveland Ave (Issued)0.27 mi N
Active in "Issued" for 9.7 yr (first record Feb 21, 2017) with no new permit activity recorded in 2.3 yr. High-impact scale (1 housing unit, $875,000 declared valuation across 1 permit).
- Accessory dwelling unit at 131 Yale Ave A (Issued)0.47 mi N
Active in "Issued" for 4.8 yr (first record Jan 19, 2022) with no new permit activity recorded in 3.4 yr. High-impact scale (1 housing unit, $1,000,000 declared valuation across 1 permit).
- Accessory dwelling unit at 242 Morning Sun Ave (Applied)0.15 mi N
In "Applied" for 2 yr (since Nov 21, 2024), 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: Charles Window And Door (2 on parcel, 2 in ½ mi · Windows / doors / siding); Lapje Roofing (1 on parcel, 1 in ½ mi · Roof replacement); Safe And Warm Chimney Service (1 on parcel, 1 in ½ mi · HVAC / heat pump); Arb (1 on parcel, 1 in ½ mi · Plumbing / water heater / sewer); Owner Builder (83 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (6 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| 91238 | Addition (adds square footage) | Applied | App. Jun 22, 2023 | $120,000 | Detached Addition |
| B23536 | Roof replacement | Issued | Iss. Sep 21, 2020 | $10,800 | REMOVE ROOFING BUILD UP DOWN TO EXISTING SHEATHING SURFACE. REMOVE CONNECTING SHEET METAL ACCESSORIES AND HAUL AWAY DEBR… |
| B19804 | Plumbing / water heater / sewer | Issued | Iss. Sep 9, 2019 | $2,500 | Extend gas house line for meter relocation — New Plumbing Fixture(s) |
| 157013 | HVAC / heat pump | Issued | Iss. Nov 8, 2017 | $6,200 | Install Gas Insert, Gas Line & Elect For Blower |
| 153194 | Windows / doors / siding | Issued | Iss. Sep 7, 2016 | $7,950 | Repl Patio Door; Cut Down 2' For New Patio Door & Header - Express***Expired |
| 144596 | Windows / doors / siding | Issued | Iss. Oct 21, 2014 | $2,469 | Repl 4 Wndws Size For Size - Must Meet W U I And Egress Requirements***Expired*** |