Mill Valley 94941 · Alto · APN 033-091-31 · Unincorporated Marin
Zoned RA-B2 in Unincorporated Marin with likely ministerial ADU eligibility and mapped FEMA AO flood due diligence; benchmark value $2,204,000 ($1,940,000–$2,468,000).
Zone RA-B2 allows residential use qualifying for ministerial ADU review under state law (3 ADU permits permitted within ¼ mile in 36 months).
Source: Unincorporated Marin zoning · CA Gov. Code 66314
On-parcel permit history is indexed through Mar 11, 2024, 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)
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.
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.
$2,204,000
Benchmark range: $1,940,000 – $2,468,000
Accessory dwelling unit at 70 Shell Rd: In "Applied" for 4.2 yr (since Aug 18, 2022), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (review-time benchmark)
Closest lead: New home at 30 Shell Rd (0.26 mi E, 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 (~$2,150/mo). Confirm exact Mello-Roos / CFD special assessments on the county tax bill.
Source: CA Const. Art. XIIIA (Prop 13) · County Tax Collector
76 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.
In "Applied" for 4.2 yr (since Aug 18, 2022), with no new permit record in 3.7 yr. · 1 unit · $300,000 declared valuation
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 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)
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)
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
30 Shell Rd · 1 unit · $2,800,000 valuation
Records span Jul 5, 2024 to Jan 3, 2025 (1 permit).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
30 Shell Rd (Adu 30a) · 1 unit · $500,000 valuation
Records span Jul 23, 2024 to Jan 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 4.2 yr (since Aug 18, 2022), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
Pending in review for 4.2 yr (7.6× the 204d median) — slower than 90% of accessory dwelling unit (new or conversion) permits in Unincorporated Marin (median 204d, 90th pct 549d, n=298).
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 |
|---|---|---|---|---|
| Window And Door Factory Of California | Windows / doors / siding | 1 on parcel1 in ½ mi | $22,000 | 0 vs 0 prior |
| Cost U Less Roofing | Roof replacement | 1 on parcel1 in ½ mi | $13,750 | 0 vs 0 prior |
| Divine Electric | EV charger | 1 on parcel1 in ½ mi | $4,200 |
| 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)On this parcel | 298 | 120d | 204d | 331d | 549d | 214d(vs 181d prior) |
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 ($22,050/yr) + local voter-approved bond debt ($3,308/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.
−$126,216/yr
Cash needed: $485,100
NOI: $7,580/yr
P&I: $11,150/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 | −$10,972/mo | -27.1% | $18,949/mo | −$11,015/mo |
| Base (your inputs) | Your entered assumptions, 3.0%/yr rent growth | $3,950/mo | −$10,518/mo | -26.0% | $17,539/mo | −$10,337/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 | −$10,258/mo | -25.4% | $17,132/mo | −$9,822/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.
Applied1 unitsAug 18, 2022 – Mar 17, 2023
We group related permits and State housing reports into projects. That grouping is our inference, not an official record.
Replace 15 windows and 1 patio sliding glass door like for like — Non-structural Door/Window Replacement
Replace 100 AMP Main Service Panel with new 200 AMP Main service Panel in same location. Install 40 AMP Electric Vehicle charger. — Service Upgrade, EV Charging Station
Detached A D U
Tear off existing roof material. Install new Class A fire rated dimensional composition cool roof shingles - 25 sq. — ReRoofing
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.
| Report year | Project / record | Type | Entitled | Permitted | Completed | Deed-restricted |
|---|---|---|---|---|---|---|
| 2023 | —(P4008) | ADU · Renter | 1 (Mar 17, 2023) | — | — | — |
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
0.31 acres
Assessor's classification for assessment purposes. This is not zoning.
70A SHELL RD; 70 SHELL RD
Source: County of Marin GIS (MarinMap), Parcels · Geography: parcel · Retrieved Nov 13, 2026
Search by parcel number 033-091-31. Assessed value is not market value.
Search by parcel number 033-091-31 (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) | Addition (adds square footage) | 18 in ½ mi | $2,351,800 | 226 vs 240 prior−6% |
| Owner Recent nearby: 3 Plaza Dr (Feb 19, 2021) | Addition (adds square footage) | 9 in ½ mi | $1,209,090 | 25 vs 15 prior+67% |
| Kurt Jehling Construction Recent nearby: 14 Lomita Dr (Jan 12, 2021) | Remodel / interior alteration | 4 in ½ mi | $220,000 | 0 vs 0 prior |
| Drosihn Construction Recent nearby: 41 Shell Rd (Dec 10, 2015) | New garage / accessory structure | 3 in ½ mi | $805,000 | 0 vs 0 prior |
| Van Houten Construction Recent nearby: 57 Shell Rd (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 |
| Addition (adds square footage) | 316 | 103d | 160d | 249d | 440d | 157d(vs 167d 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) |
| EV chargerOn this parcel | 482 | 0d | 0d | 0d | 0d | 0d |
| Roof replacementOn this parcel | 3,663 | 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.