Mill Valley 94941 · Alto · APN 033-092-15 · Unincorporated Marin
Zoned RA-B2 in Unincorporated Marin with likely ministerial ADU eligibility and mapped FEMA AO flood due diligence; benchmark value $2,201,000 ($1,937,000–$2,465,000).
Zone RA-B2 allows residential use qualifying for ministerial ADU review under state law (10 ADU permits permitted within ¼ mile in 36 months).
Source: Unincorporated Marin zoning · CA Gov. Code 66314
Public building records show issued construction/renovation work on this parcel (3 total permits, latest Jun 8, 2026).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
Zone AO: 1% annual chance flood (Special Flood Hazard Area) overlaps this parcel. Expect mandatory flood insurance for federally backed loans and floodplain elevation/mitigation rules for new units or SB 9 applications.
Source: FEMA National Flood Hazard Layer (parcel polygon)
Automated synthesis of indexed municipal, county, state, and federal public records — informational context only, not a formal appraisal, survey, or legal/tax determination.
$2,201,000
Benchmark range: $1,937,000 – $2,465,000
Remodel / interior alteration (181832): Issued after 2.3 yr (9.9× the 83d median) — slower than 90% of remodel / interior alteration permits in Unincorporated Marin (median 83d, 90th pct 266d, n=1,054).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (review-time benchmark)
Closest lead: New home at 55 Thomas Dr (0.39 mi E, applied). 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 (~$2,147/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: 2 homes completed, 5 permitted, 3 proposed or in review.
10 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.
140 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 13, 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 13, 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 RA-B2 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 12.7 yr (first record Mar 13, 2014), with no completion or new permit record in 12.6 yr. · $6,450 declared valuation
Permit issued and active for 12.9 yr (first record Dec 19, 2013), with no completion or new permit record in 12.6 yr. · 1 unit · $445,000 declared valuation
Permit issued and active for 12.7 yr (first record Mar 6, 2014), with no completion or new permit record in 12.3 yr. · 1 unit · $174,000 declared valuation
Permit issued and active for 12.4 yr (first record Jun 30, 2014), with no completion or new permit record in 12.2 yr. · 1 unit · $685,000 declared valuation
Permit issued and active for 12.5 yr (first record May 13, 2014), with no completion or new permit record in 11.3 yr. · 1 unit · $350,000 declared valuation
Permit issued and active for 10.5 yr (first record May 25, 2016), with no completion or new permit record in 10.1 yr. · 1 unit · $650,000 declared valuation
Nearby other (50 Shell Rd): First appeared in published agency feed
Record B49028 · 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) (29 Meadow Dr): First appeared in published agency feed
Record 182865 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Record 94052 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
54 Shell Rd · 1 unit · $182,160 valuation
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
Latest published Zillow Home Value Index (ZHVI) update
Changed from $1,980,059 in September 2025 to $2,181,389 in September 2026.
Source: Zillow Home Value Index (ZHVI) · Data provided by Zillow · Geography: ZIP 94941 (not a parcel appraisal)
Remodel / interior alteration permit issued (181832)
Recorded status: Issued
Remodel Bathrm Incl Roof Replacement, (N) Windows & Doors; (N) Deck W/Spa; Driveway Resurface & Landscaping; Spa · Declared valuation: $100,000 · Contractor: Mastec Communicaitons Group
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Geography: parcel
Roof replacement permit application filed (B46595)
Current status: Issued
ReRoofing · Declared valuation: $20,000 · Contractor: Rooflow Inc
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Geography: parcel
Roof replacement permit issued (B46595)
Recorded status: Issued
ReRoofing · Declared valuation: $20,000 · Contractor: Rooflow Inc
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Geography: parcel
29 Meadow Dr · 1 unit · $3,000 valuation
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
13 Shell Rd · 1 unit · $100,000 valuation
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
12 Shell Rd (A D U 12 A) · 1 unit · $8,000 valuation
Records span Mar 3, 2023 to Oct 15, 2025 (1 permit).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
Annual ZIP 94941 home-value index checkpoint
Changed from $2,042,452 in September 2024 to $1,980,059 in September 2025.
Source: Zillow Home Value Index (ZHVI) · Data provided by Zillow · Geography: ZIP 94941 (not a parcel appraisal)
1 unit
Records span Mar 4, 2024 to Sep 16, 2025 (0 permits).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
16 Shell Rd ( Adu 16a) · 1 unit · $300,000 valuation
Records span Mar 7, 2025 to Jul 17, 2025 (1 permit).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
55 Plaza Dr (Adu 55a) · 1 unit · $790,000 valuation
Records span Apr 17, 2024 to Apr 3, 2025 (1 permit).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project 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 →In "Applied" for 6.2 yr (since Sep 1, 2020), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121). High-impact scale (1 housing unit, $1,000,000 declared valuation across 1 permit).
Issued after 2.3 yr (9.9× the 83d median) — slower than 90% of remodel / interior alteration permits in Unincorporated Marin (median 83d, 90th pct 266d, n=1,054).
Active in "Issued" for 2.4 yr (first record Jul 5, 2024) with no new permit activity recorded in 22 mo. High-impact scale (1 housing unit, $2,800,000 declared valuation across 1 permit).
Active in "Issued" for 2.6 yr (first record Apr 17, 2024) with no new permit activity recorded in 19 mo. High-impact scale (1 housing unit, $790,000 declared valuation across 1 permit).
In "Applied" for 6.7 yr (since Feb 20, 2020), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
In "Applied" for 2.7 yr (since Mar 4, 2024), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
| Builder / contractor | Primary specialty | Here / ½ mi | ½ mi valuation | Citywide 24m trend |
|---|---|---|---|---|
| Mastec Communicaitons Group | Remodel / interior alteration | 1 on parcel1 in ½ mi | $100,000 | 10 vs 0 prior |
| Rooflow | Roof replacement | 1 on parcel1 in ½ mi | $20,000 | 0 vs 0 prior |
| The Plumbing Two | Plumbing / water heater / sewer | 1 on parcel1 in ½ mi | $9,817 | 0 |
| Permit category | Sample (n) | 25th pct | Median (50th) | 75th pct | 90th pct | Recent 24m median |
|---|---|---|---|---|---|---|
| New single-family home | 121 | 166d | 253d | 456d | 686d | 211d(vs 273d 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 ($22,000/yr) + local voter-approved bond debt ($3,300/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.
−$125,855/yr
Cash needed: $484,000
NOI: $7,638/yr
P&I: $11,124/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 | −$10,942/mo | -27.1% | $18,907/mo | −$10,984/mo |
| Base (your inputs) | Your entered assumptions, 3.0%/yr rent growth | $3,950/mo | −$10,488/mo | -26.0% | $17,500/mo | −$10,307/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 | −$10,227/mo | -25.4% | $17,094/mo | −$9,791/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.
Remodel Bathrm Incl Roof Replacement, (N) Windows & Doors; (N) Deck W/Spa; Driveway Resurface & Landscaping; Spa
ReRoofing
CombiBoiler Swap — Replace Plumbing Fixtures(s)
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Geography: parcel (APN) · Retrieved Nov 13, 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 13, 2026
0.22 acres
Assessor's classification for assessment purposes. This is not zoning.
39 SHELL RD
Source: County of Marin GIS (MarinMap), Parcels · Geography: parcel · Retrieved Nov 13, 2026
Search by parcel number 033-092-15. Assessed value is not market value.
Search by parcel number 033-092-15 (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.
| Owner Builder Recent nearby: 29 Meadow Dr (Nov 2, 2026) | Remodel / interior alteration | 34 in ½ mi | $3,575,300 | 226 vs 240 prior−6% |
| Owner Recent nearby: 25 Knoll Ln (Mar 30, 2022) | Remodel / interior alteration | 20 in ½ mi | $1,703,090 | 25 vs 15 prior+67% |
| Drosihn Construction Recent nearby: 31 N Knoll Rd A K A 29c (May 8, 2017) | New single-family home | 6 in ½ mi | $2,191,000 | 0 vs 0 prior |
| Kurt Jehling Construction Recent nearby: 14 Lomita Dr (Jan 12, 2021) | Remodel / interior alteration | 4 in ½ mi | $220,000 | 0 vs 0 prior |
| Van Houten Construction Recent nearby: 57 Shell Rd #A (Oct 10, 2016) | Accessory dwelling unit (new or conversion) | 3 in ½ mi | $789,000 | 0 vs 0 prior |
| Plr Builders Recent nearby: 16 Shell Rd (Apr 16, 2026) | Accessory dwelling unit (new or conversion) | 3 in ½ mi | $623,000 | 5 vs 0 prior |
| Nafius Construction Service Recent nearby: 24 Shell Rd (Sep 27, 2016) | Addition (adds square footage) | 3 in ½ mi | $177,500 | 0 vs 0 prior |
| 316 |
| 103d |
| 160d |
| 249d |
| 440d |
| 157d(vs 167d prior) |
| Remodel / interior alterationOn this parcel | 1,054 | 36d | 83d | 148d | 266d | 112d(vs 77d prior) |
| Commercial tenant improvement | 81 | 99d | 148d | 233d | 443d | 152d(vs 150d prior) |
| Roof replacementOn this parcel | 3,663 | 0d | 0d | 0d | 0d | 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.