Mill Valley 94941 · Tamalpais · APN 050-252-16 · Unincorporated Marin
Zoned R1-B1 in Unincorporated Marin with likely ADU & SB 9 infill eligibility and mapped CAL FIRE high fire hazard severity zone (local responsibility area) due diligence; benchmark value $2,040,000 ($1,795,000–$2,285,000).
Zoned R1-B1 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 5,053 sq ft lot. Local precedent is active with 5 ADU permits within ¼ mile over the last 36 months.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
On-parcel permit history is indexed through Oct 22, 2020, 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)
50 substantial renovation & housing permits over 24 months (20.5 per 1,000 parcels vs. 16.3 citywide baseline) (#3 of 22 neighborhoods).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (Tamalpais)
Automated synthesis of indexed municipal, county, state, and federal public records — informational context only, not a formal appraisal, survey, or legal/tax determination.
$2,040,000
Benchmark range: $1,795,000 – $2,285,000
about 81% 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)
Located in a mapped Fire Hazard Severity Zone. Expect Chapter 7A ignition-resistant building standards, defensible-space inspections, and stricter property insurance underwriting.
Source: CAL FIRE FHSZ (map Mar 24, 2025)
Closest lead: Accessory dwelling unit at 403 Marin Ave (adu 403a) (460 ft 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)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,993/mo). Confirm exact Mello-Roos / CFD special assessments on the county tax bill.
Source: CA Const. Art. XIIIA (Prop 13) · County Tax Collector
Since November 2024 within ½ mile: 1 homes completed, 14 permitted, 10 proposed or in review; 1 demolition.
26 projects with a record in this window, grouped by us from permits and State housing reports. Units are as proposed on each project's latest record and counted at its current stage.
564 permits within ½ mile since November 2024
The map shows new construction, ADUs, demolitions, additions, and renovations. Routine systems work (roofs, HVAC, water heaters) is counted but not mapped. Unit counts are as stated on permits.
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Geography: permits located by parcel, ½ mile radius · Retrieved Nov 14, 2026
Public-records benchmark estimate combining Zillow Home Value Index (Data provided by Zillow), Census ACS 5-year estimates, parcel land-use/lot characteristics, and issued building permits. Not an official appraisal.
Permit counts, by the date issued (or applied, if not yet issued). Lot splits are planning cases, which we don't have.
We read public zoning and hazard maps against state law (ADUs: Gov. Code 66314; SB 9: Gov. Code 65852.21 and 66411.7). Local rules, title, tenancy history and site conditions can change the answer. Check with Unincorporated Marin's planning department before relying on it.
Sources: County of Marin GIS (MarinMap), Zoning (11 cities and unincorporated Marin) (retrieved Nov 14, 2026) · CAL FIRE Office of the State Fire Marshal, Fire Hazard Severity Zones in the State Responsibility Area (effective 2024-04-01) (retrieved Nov 9, 2026) · CAL FIRE Office of the State Fire Marshal, Fire Hazard Severity Zones in the Local Responsibility Area (map dated 2025-03-24) (retrieved Nov 9, 2026) · FEMA, National Flood Hazard Layer — flood hazard zones (retrieved Nov 9, 2026) · FEMA, National Flood Hazard Layer — FIRM panels (retrieved Nov 9, 2026) · California Geological Survey, Alquist-Priolo Earthquake Fault Zones (retrieved Nov 9, 2026) · Zoning classes: our classification of R1-B1 as single-family residential, checked against the zone description on Oct 24, 2026
Chronological history of building permit applications and issuances, snapshot-dated status changes, State housing entitlements, surrounding development within ½ mile, and area home-value trends.
Permit issued and active for 7.1 yr (first record Oct 21, 2019), with no completion or new permit record in 6.8 yr. · 1 unit · $15,000 declared valuation
Permit issued and active for 7.3 yr (first record Aug 13, 2019), with no completion or new permit record in 6 yr. · 1 unit · $600,000 declared valuation
Permit issued and active for 6.1 yr (first record Oct 13, 2020), with no completion or new permit record in 5.8 yr. · 1 unit · $150,000 declared valuation
In "Entitled" for 5.6 yr (since Mar 31, 2021), with no new permit record in 5.6 yr. · 1 unit
Permit issued and active for 5.7 yr (first record Mar 1, 2021), with no completion or new permit record in 5.3 yr. · 1 unit · $25,000 declared valuation
Permit issued and active for 5.6 yr (first record Mar 30, 2021), with no completion or new permit record in 5.3 yr. · 1 unit · $350,000 declared valuation
Nearby remodel / interior alteration (303 Dawn Ct): Description text was updated
Record 94638 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (4 Leo Ln): First appeared in published agency feed
Record B49100 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (403 Marin Ave): First appeared in published agency feed
Record B49090 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby accessory dwelling unit (new or conversion) (3 Leo Ln (Aka 3 A)): First appeared in published agency feed
Record 182940 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby remodel / interior alteration (303 Dawn Ct): Description text was updated
Record 94638 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby roof replacement (4 Leo Ln): First appeared in published agency feed
Record B49080 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Record 94306 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby remodel / interior alteration (303 Dawn Ct): First appeared in published agency feed
Record 94638 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (358 Starling Rd): First appeared in published agency feed
Record B49046 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby roof replacement (330 Tennessee Ave): First appeared in published agency feed
Record B49023 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby accessory dwelling unit (new or conversion) (254 Cleveland Ave): First appeared in published agency feed
Record 94629 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Record 94571 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (402 Countyview Dr): First appeared in published agency feed
Record 94624 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (386 Pinehill Rd): First appeared in published agency feed
Record B48997 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (552 Shoreline Hwy): First appeared in published agency feed
Record B48968 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Cross-referenced intelligence from our historical development graph—connecting parcels, permits, entity-resolved builders, empirical review-time distributions, and neighborhood renovation trends.
Explore full Unincorporated Marin development graph →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).
Active in "Issued" for 6.1 yr (first record Oct 22, 2020) with no new permit activity recorded in 22 mo. High-impact scale (1 housing unit, $980,000 declared valuation across 1 permit).
Active in "Issued" for 18 mo (first record May 12, 2025) with no new permit activity recorded in 15 mo. High-impact scale (1 housing unit, $955,000 declared valuation across 1 permit).
Active in "Issued" for 3.3 yr (first record Jul 19, 2023) with no new permit activity recorded in 2.3 yr. High-impact scale (1 housing unit, $1,183,700 declared valuation across 2 permits).
In "Applied" for 2.1 yr (since Oct 25, 2024), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
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).
Substantial improvements (additions, interior remodels, ADUs, commercial TI, and new builds) across 2,439 parcels
−7.7% YoY
City baseline: 16.3 / 1k
50 in trailing 24m
Includes 16 ADUs
| Builder / contractor | Primary specialty | Here / ½ mi | ½ mi valuation | Citywide 24m trend |
|---|---|---|---|---|
| Owner | Remodel / interior alteration | 2 on parcel56 in ½ mi | $4,400,819 | 25 vs 15 prior+67% |
| Peterson Power And Light | Electrical / panel | 1 on parcel1 in ½ mi | $7,500 | 0 vs 0 prior |
| Owner Builder Recent nearby: 312 Dolan Ave (Oct 16, 2026) | Remodel / interior alteration | 90 in ½ mi |
| Permit category | Sample (n) | 25th pct | Median (50th) | 75th pct | 90th pct | Recent 24m median |
|---|---|---|---|---|---|---|
| New single-family home | 121 | 166d | 253d | 456d | 686d | 210d(vs 276d prior) |
| New multifamily / condos / mixed-use | 21 | 272d | 292d | 293d | 313d | 293d(vs 197d prior) |
| Accessory dwelling unit (new or conversion) | 298 | 120d | 204d | 331d | 549d | 214d(vs 181d prior) |
| Addition (adds square footage) |
HUD Small Area Fair Market Rent · ZIP 94941
HUD FY 2026 · 40th-percentile gross rentCensus ACS 5-year median gross rent (all bedroom counts combined):
Area home-value benchmarks (not an appraisal)
ZIP & neighborhood mediansUnder California Proposition 13, the seller's historical assessed value does not carry over to a buyer. On sale, the parcel is reassessed at the purchase price: 1.00% base rate ($20,400/yr) + local voter-approved bond debt ($3,060/yr) + fixed direct levies/Mello-Roos ($450/yr).
Mapped hazard zone insurance context on this parcel:
Model adding a backyard ADU or garage conversion under California's Prop 13 blended new-construction assessment (existing house & land tax base stays intact; only ADU build cost is assessed) and SB 13 impact-fee rules.
−$114,307/yr
Cash needed: $448,800
NOI: $9,478/yr
P&I: $10,315/mo
For $0/mo net cash flow
At $3,950/mo gross rent
| Scenario | Assumptions | Year 1 Rent | Year 1 Cash Flow | Cash-on-Cash | Break-Even Rent | Year 5 Cash Flow |
|---|---|---|---|---|---|---|
| Conservative | −8% starting rent, +3% vacancy, +3% combined maintenance/CapEx, 1.5%/yr rent growth | $3,634/mo | −$9,979/mo | -26.7% | $17,564/mo | −$10,009/mo |
| Base (your inputs) | Your entered assumptions, 3.0%/yr rent growth | $3,950/mo | −$9,526/mo | -25.5% | $16,257/mo | −$9,332/mo |
| Optimistic (cap-limited) | +6% starting rent, 3% vacancy, 4.5%/yr rent growth (capped by AB 1482 ceiling of 8.6%/yr) | $4,187/mo | −$9,265/mo | -24.8% | $15,879/mo | −$8,816/mo |
Rental regulatory context (informational only — not legal advice):
California AB 1482 (Tenant Protection Act, Civ. Code § 1947.12) caps annual rent increases at 5% + local CPI (max 10%) on covered properties.
Replace existing electrical - old wires and poor workmanship — New Circuits / Outlets, Replace Circuits / Outlets
Replace existing plumbing - 80 year old cast iron drains are leaking, copper has tested positive for lead solder. Need to demo sheetrock in bathroom and a closet to access pipes, would like to replace sheetrock and compromised tile in bathroom at the same time. Remove old tank water heater from indoor closet and replace with new tankless mounted outside. Remove 1st generation tankless from indoor closet and replace with new tankless mounted outside. Replace compromised boards on exterior siding. Replace compromised front stairs. — Replace Plumbing Fixtures(s); Siding Replacement, Non-structural Door/Window Replacement
Provide and install new 200amp overhead electrical service and re-feed the existing 2 units. Install new sub panel feed to lower kitchen and re-feed existing kitchen and bath circuits. Provide GFI plugs for 2 on demand water heaters. — Service Upgrade, Replace Circuits / Outlets
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Geography: parcel (APN) · Retrieved Nov 14, 2026 · Received and issued dates come from the County of Marin. The county publishes no final or expired status, so an issued permit stays 'Issued' after the work is done.
No housing activity reported to the State for this parcel (2018–2025 reports).
Source: California HCD, Housing Element Annual Progress Report — Table A2 · Geography: project (parcel) · Retrieved Nov 9, 2026 · From Unincorporated Marin's Housing Element Annual Progress Reports. A project can appear in several report years as it moves from entitlement to permit to completion.
Source: County of Marin GIS (MarinMap), Zoning (11 cities and unincorporated Marin) · Geography: zoning district polygon at parcel point · Retrieved Nov 14, 2026
0.12 acres
Assessor's classification for assessment purposes. This is not zoning.
378 MARIN AVE
Source: County of Marin GIS (MarinMap), Parcels · Geography: parcel · Retrieved Nov 14, 2026
Search by parcel number 050-252-16. Assessed value is not market value.
Search by parcel number 050-252-16 (Marin County Tax Collector)
Permits issued in unincorporated Marin in the past 48 months. Each city keeps its own records.
The official flood hazard map for this location. Our reading of it is under What could be built here.
This site does not show owner names.
| $9,623,379 |
| 226 vs 240 prior−6% |
| International Building Investment Recent nearby: 396 Pine Hill Rd #37 (May 31, 2017) | Remodel / interior alteration | 12 in ½ mi | $173,200 | 0 vs 0 prior |
| Leon Construction Recent nearby: 396 Pinehill Rd #10 (Sep 9, 2014) | Remodel / interior alteration | 7 in ½ mi | $224,000 | 0 vs 0 prior |
| Barton Design And Constuction Recent nearby: 406 Wendy Way (Oct 21, 2022) | Addition (adds square footage) | 6 in ½ mi | $1,525,000 | 0 vs 0 prior |
| Lamperti Contracting And Design Recent nearby: 370 Dolan Ave (Feb 15, 2024) | Remodel / interior alteration | 6 in ½ mi | $452,511 | 2 vs 7 prior |
| Salgo Constructions Recent nearby: 291 Morning Sun Ave (Jan 23, 2019) | Remodel / interior alteration | 5 in ½ mi | $141,500 | 0 vs 0 prior |
| Pmm Construction Recent nearby: 295 Greene St (Mar 11, 2021) | Accessory dwelling unit (new or conversion) | 4 in ½ mi | $775,000 | 0 vs 0 prior |
| Christensen Construction Recent nearby: 3 Leo Ln (Aka 3 A) (Nov 10, 2026) | Remodel / interior alteration | 4 in ½ mi | $460,000 | 1 vs 0 prior |
| 316 |
| 103d |
| 160d |
| 249d |
| 440d |
| 159d(vs 166d prior) |
| Remodel / interior alteration | 1,054 | 36d | 83d | 148d | 266d | 112d(vs 77d prior) |
| Commercial tenant improvement | 81 | 99d | 148d | 233d | 443d | 152d(vs 150d prior) |
| Electrical / panelOn this parcel | 3,020 | 0d | 0d | 0d | 2d | 0d |
| Plumbing / water heater / sewerOn this parcel | 2,211 | 0d | 0d | 0d | 0d | 0d |
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Computed from issued permits with recorded application and issuance dates over the trailing 60 months. Categories with fewer than 20 permits are excluded.