312 Morning Sun Ave
Mill Valley 94941 · Tamalpais · Unincorporated Marin · Coordinates: 37.88057, -122.52949
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 $2,094,000 ($1,843,000–$2,345,000).
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 7,013 sq ft lot. Local precedent is active with 11 ADU permits 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 Jun 16, 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)
- ✓ Above-average reinvestment in Tamalpais
50 substantial renovation & housing permits over 24 months (20.5 per 1,000 parcels vs. 16.4 citywide baseline) (#3 of 22 neighborhoods).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (Tamalpais)
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: New home at 217 Cleveland Ave (0.32 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 (~$24,531/yr at $2,094,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$2,044/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:
- 7,013 sq ft (0.16 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 312 MORNING SUN AVE
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 7,013 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: $1,843,000 – $2,345,000 · 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)
22 active or recent development projects (20 housing units across completed, permitted, and pipeline stages) and 594 total building permits recorded within ½ mile.
- New construction18 permits (2 units)
- Adds housing (ADU)18 permits (18 units)
- Demolition1 permit
- Additions & renovations39 permits
- Building systems416 permits
- Repairs31 permits
- Other71 permits
Developments Deserving Closer Investigation & Active Area Builders
- New home at 217 Cleveland Ave (Issued)0.32 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 403 Marin Ave (adu 403a) (Issued)0.39 mi SW
Active in "Issued" for 2.9 yr (first record Dec 21, 2023) with no new permit activity recorded in 19 mo. High-impact scale (1 housing unit, $1,000,000 declared valuation across 1 permit).
- Accessory dwelling unit at 384 Woodside Ave (Applied)0.25 mi W
In "Applied" for 2 yr (since Oct 25, 2024), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- New home at 249 Perry St (Applied)0.26 mi NE
In "Applied" for 2 yr (since Oct 31, 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: Westco Roofing (1 on parcel, 1 in ½ mi · Roof replacement); Ernest Ongaro And Sons (1 on parcel, 1 in ½ mi · Other); Reggies Reliable Plumbing Service (1 on parcel, 1 in ½ mi · Plumbing / water heater / sewer); Owner Builder (95 in ½ mi · Remodel / interior alteration); Owner (56 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (3 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B34330 | Roof replacement | Issued | Iss. Jun 16, 2023 | $23,000 | Removal of existing roofing materials down to the existing sheathing and installation of new class A architectural shing… |
| B20433 | Other | Issued | Iss. Nov 22, 2019 | $8,000 | Replace 2 failed furnaces with 2 new furnaces- one to service main house and the other to service the attached studio — … |
| B11700 | Plumbing / water heater / sewer | Issued | Iss. Jan 19, 2017 | $5,297 | Install new 50 gal. water heater to replace old. — Replace Plumbing Fixtures(s) |