Mill Valley 94941 · Tamalpais · APN 200-252-25 · Unincorporated Marin
Zoned RSP-4 in Unincorporated Marin with likely ADU & SB 9 infill eligibility and mapped CAL FIRE high fire hazard severity zone (state responsibility area) due diligence; benchmark value $2,158,000 ($1,899,000–$2,417,000).
Zoned RSP-4 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 9,191 sq ft lot. Local precedent is active with 2 ADU permits within ¼ mile over the last 36 months.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
Public building records show issued construction/renovation work on this parcel (7 total permits, latest Mar 14, 2024).
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. 16.4 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.
$2,158,000
Benchmark range: $1,899,000 – $2,417,000
about 66% 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)
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 Apr 1, 2024)
Closest lead: New home at 535 Tennessee Valley Rd (adu 531) (0.28 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 (~$2,106/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, 3 permitted, 3 proposed or in review; 1 demolition.
8 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.
296 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 RSP-4 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 9.6 yr (since Mar 20, 2017), with no new permit record in 9.6 yr. · $250,000 declared valuation
Permit issued and active for 9.6 yr (first record Mar 28, 2017), with no completion or new permit record in 9.6 yr. · $250 declared valuation
Permit issued and active for 9.6 yr (first record Apr 11, 2017), with no completion or new permit record in 9.6 yr. · $45,000 declared valuation
In "Applied" for 7.4 yr (since Jun 25, 2019), with no new permit record in 7.4 yr. · 1 unit · $120,000 declared valuation
Permit issued and active for 8.1 yr (first record Oct 8, 2018), with no completion or new permit record in 7.3 yr. · 1 unit · $40,000 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
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 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 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 new garage / accessory structure (359 Durant Way): Contractor changed from (blank) to BOLT DOWN THE BAY AREA
Record 182828 · 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 plumbing / water heater / sewer (400 Tennessee Glen Way): First appeared in published agency feed
Record B49038 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (341 Durant Way): First appeared in published agency feed
Record B49036 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby electrical / panel (301 Tennessee Valley Rd): First appeared in published agency feed
Record B49005 · 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 plumbing / water heater / sewer (343 Durant Way): First appeared in published agency feed
Record B48846 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby new garage / accessory structure (359 Durant Way): First appeared in published agency feed
Record 182828 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (359 Durant Way): No longer present in latest agency feed
Record 94342 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby roof replacement (385 Countyview Dr): First appeared in published agency feed
Record B48891 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby electrical / panel (354 Starling Rd): First appeared in published agency feed
Record B48885 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (314 Durant Way): First appeared in published agency feed
Record B48877 · 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 6 yr (first record Oct 29, 2020) with no new permit activity recorded in 4 yr. High-impact scale (1 housing unit, $800,000 declared valuation across 1 permit).
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).
In "Applied" for 5.2 yr (since Sep 3, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
In "Applied" for 7.4 yr (since Jun 25, 2019), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
In "Entitled" for 5.6 yr (since Mar 31, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
Active in "Applied" for 13 mo (first record Oct 21, 2025) with no new permit activity recorded in 13 mo.
Substantial improvements (additions, interior remodels, ADUs, commercial TI, and new builds) across 2,439 parcels
−7.7% YoY
City baseline: 16.4 / 1k
50 in trailing 24m
Includes 16 ADUs
| Builder / contractor | Primary specialty | Here / ½ mi | ½ mi valuation | Citywide 24m trend |
|---|---|---|---|---|
| Owner Builder | Remodel / interior alteration | 1 on parcel40 in ½ mi | $4,400,243 | 226 vs 240 prior−6% |
| Owner | Remodel / interior alteration | 1 on parcel26 in ½ mi | $1,684,600 | 25 vs 15 prior+67% |
| Jaj Roofing | Solar / battery storage | 3 on parcel |
| 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 ($21,600/yr) + local voter-approved bond debt ($3,240/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.
−$122,968/yr
Cash needed: $475,200
NOI: $8,098/yr
P&I: $10,922/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 | −$10,701/mo | -27.0% | $18,572/mo | −$10,741/mo |
| Base (your inputs) | Your entered assumptions, 3.0%/yr rent growth | $3,950/mo | −$10,247/mo | -25.9% | $17,189/mo | −$10,063/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 | −$9,987/mo | -25.2% | $16,790/mo | −$9,547/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.
Install James Hardie fiber cement siding to all exterior walls of home. Approx. 4100 sq.ft. — Siding Replacement
Water Heater Replacement with Same — Replace Plumbing Fixtures(s); Replace Mechanical Appliance
Retaining Wall - Emergency
PV Solar roof mount 6.40kW with 16 Panels and 16 Micro Inverters, With New 24A PV Breaker
Removal of existing roof membrane down to the insulation. Install 1 layer of ¼” DensDeck mechanically attached with screws and plates. Install white 60 mil IB PVC roof membrane, mechanically attached with heat-welded seams. — ReRoofing
Install New Battery System of 27KWH Wall Mounted
Replace 2 Furnaces W/Duct Work
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
0.21 acres
Assessor's classification for assessment purposes. This is not zoning.
303 ASHTON LN
Source: County of Marin GIS (MarinMap), Parcels · Geography: parcel · Retrieved Nov 13, 2026
Search by parcel number 200-252-25. Assessed value is not market value.
Search by parcel number 200-252-25 (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.
| $70,830 |
| 0 vs 0 prior |
| Rps Remodeling | Windows / doors / siding | 1 on parcel1 in ½ mi | $42,500 | 0 vs 0 prior |
| Ongaro Ernest And Sons | HVAC / heat pump | 1 on parcel1 in ½ mi | $9,800 | 0 vs 0 prior |
| Philip Kline Gen Cont Recent nearby: 318 Via Recodo (Mar 13, 2019) | Remodel / interior alteration | 6 in ½ mi | $229,000 | 0 vs 0 prior |
| Green Bay Remodeling Recent nearby: 301 Via Recodo (Mar 6, 2024) | Remodel / interior alteration | 5 in ½ mi | $210,000 | 5 vs 5 prior |
| Hunts Construction Partnership Recent nearby: 368 Shoreline Hwy (Aug 26, 2020) | Remodel / interior alteration | 4 in ½ mi | $145,000 | 0 vs 0 prior |
| Wingers Erection Recent nearby: 349 Carrera Dr (Apr 21, 2026) | Remodel / interior alteration | 3 in ½ mi | $300,000 | 1 vs 0 prior |
| Hsc Services Recent nearby: 331 Linda Way (Oct 6, 2022) | Remodel / interior alteration | 3 in ½ mi | $264,187 | 1 vs 0 prior |
| 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) |
| Solar / battery storageOn this parcel | 2,977 | 0d | 0d | 0d | 2d | 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.