Mill Valley 94941 · Homestead · APN 047-052-10 · Unincorporated Marin
Zoned R1 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 $2,222,000 ($1,955,000–$2,489,000).
Zoned R1 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 9,583 sq ft lot. Local precedent is active with 1 ADU permit 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 (2 total permits, latest Feb 21, 2024).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
22 substantial renovation & housing permits over 24 months (20.7 per 1,000 parcels vs. 16.4 citywide baseline) (#2 of 22 neighborhoods).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (Homestead)
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: 1 homes completed, 3 permitted, 4 proposed or in review.
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.
$2,222,000
Benchmark range: $1,955,000 – $2,489,000
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)
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 65 Ridge Ave (0.41 mi W, 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 (~$2,167/mo). Confirm exact Mello-Roos / CFD special assessments on the county tax bill.
Source: CA Const. Art. XIIIA (Prop 13) · County Tax Collector
133 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 R1 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 12.4 yr (first record Jun 17, 2014), with no completion or new permit record in 12.1 yr. · 1 unit · $1,100,000 declared valuation
Permit issued and active for 11.8 yr (first record Jan 13, 2015), with no completion or new permit record in 11.8 yr. · $3,000 declared valuation
Permit issued and active for 12.1 yr (first record Oct 7, 2014), with no completion or new permit record in 11.2 yr. · 1 unit · $500,000 declared valuation
In "Entitled" for 6.3 yr (since Aug 11, 2020), with no new permit record in 6.3 yr. · 1 unit
Permit issued and active for 6.9 yr (first record Dec 18, 2019), with no completion or new permit record in 5.9 yr. · 1 unit · $750,000 declared valuation
Permit issued and active for 6 yr (first record Nov 18, 2020), with no completion or new permit record in 4.7 yr. · 1 unit · $725,000 declared valuation
Nearby roof replacement (646 Ridgewood Ave): First appeared in published agency feed
Record B49103 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby electrical / panel (58 Castle Rock Dr): First appeared in published agency feed
Record B48991 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff 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)
409 Montford Ave (Adu 409a) · 1 unit · $75,000 valuation
Records span Jul 2, 2026 to Sep 24, 2026 (1 permit).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
550 Montford Ave · 1 unit · $175,000 valuation
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
1 unit
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
473 Panoramic Hwy (A D U 473a) · 1 unit
Records span Aug 21, 2025 to Nov 19, 2025 (1 permit).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
1 unit
Records span Oct 13, 2025 to Oct 23, 2025 (0 permits).
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
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
408 Laverne Ave (Adu 408a) · 1 unit · $2,700,000 valuation
Records span Jul 12, 2024 to Aug 29, 2025 (1 permit).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
1 unit
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 $2,038,275 in September 2023 to $2,042,452 in September 2024.
Source: Zillow Home Value Index (ZHVI) · Data provided by Zillow · Geography: ZIP 94941 (not a parcel appraisal)
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) & HCD APR (grouped project within ½ mile)
Roof replacement permit application filed (B37085)
Current status: Issued
T/O existing roof, install new GAF comp shingle on 1700 sq ft, haul away debris — ReRoofing · Declared valuation: $20,000 · Contractor: Sunshine Roofing
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Geography: parcel
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 yr (since Oct 27, 2022), 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, $3,000,000 declared valuation across 1 permit).
In "Entitled" for 6.3 yr (since Aug 11, 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 deed-restricted affordable across 0 permits).
Active in "Issued" for 8.6 yr (first record Apr 23, 2018) with no new permit activity recorded in 3.8 yr. High-impact scale (1 housing unit, $1,100,000 declared valuation across 1 permit).
Active in "Issued" for 6.9 yr (first record Dec 18, 2019) with no new permit activity recorded in 5.9 yr. High-impact scale (1 housing unit, $750,000 declared valuation across 1 permit).
Active in "Issued" for 2.3 yr (first record Jul 12, 2024) with no new permit activity recorded in 14 mo. High-impact scale (1 housing unit, $2,700,000 declared valuation across 1 permit).
Active in "Issued" for 12.4 yr (first record Jun 17, 2014) with no new permit activity recorded in 12.1 yr. High-impact scale (1 housing unit, $1,100,000 declared valuation across 2 permits).
Substantial improvements (additions, interior remodels, ADUs, commercial TI, and new builds) across 1,063 parcels
+0.0% YoY
City baseline: 16.4 / 1k
22 in trailing 24m
Includes 10 ADUs
| Builder / contractor | Primary specialty | Here / ½ mi | ½ mi valuation | Citywide 24m trend |
|---|---|---|---|---|
| Cal Summit Builders | Remodel / interior alteration | 1 on parcel1 in ½ mi | $40,000 | 0 vs 0 prior |
| Sunshine Roofing | Roof replacement | 1 on parcel1 in ½ mi | $20,000 | 0 vs 0 prior |
| Owner Builder Recent nearby: 226 Panoramic Hwy (Aug 25, 2026) | Remodel / interior alteration | 31 in ½ mi | $2,991,150 |
| 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 ($22,200/yr) + local voter-approved bond debt ($3,330/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.
−$127,299/yr
Cash needed: $488,400
NOI: $7,408/yr
P&I: $11,226/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 | −$11,062/mo | -27.2% | $19,075/mo | −$11,106/mo |
| Base (your inputs) | Your entered assumptions, 3.0%/yr rent growth | $3,950/mo | −$10,608/mo | -26.1% | $17,656/mo | −$10,428/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 | −$10,348/mo | -25.4% | $17,246/mo | −$9,913/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.
T/O existing roof, install new GAF comp shingle on 1700 sq ft, haul away debris — ReRoofing
Rmdl Kitch & Upgrade Elec Panel Express
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.
51 CASTLE ROCK DR
Source: County of Marin GIS (MarinMap), Parcels · Geography: parcel · Retrieved Nov 13, 2026
Search by parcel number 047-052-10. Assessed value is not market value.
Search by parcel number 047-052-10 (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.
| 226 vs 240 prior−6% |
| Owner Recent nearby: 408 Laverne Ave (Adu 408a) (Aug 29, 2025) | Remodel / interior alteration | 13 in ½ mi | $3,549,000 | 25 vs 15 prior+67% |
| Green Bay Remodeling Recent nearby: 311 Edgewood Ave (Mar 8, 2022) | Remodel / interior alteration | 3 in ½ mi | $74,000 | 5 vs 5 prior |
| Argo Construction Recent nearby: 420 Laverne Ave (Feb 2, 2023) | New single-family home | 2 in ½ mi | $1,200,000 | 0 vs 2 prior |
| Schalich Brothers Construction Recent nearby: 409 Montford Ave (Sep 29, 2014) | Demolition | 2 in ½ mi | $1,119,000 | 7 vs 1 prior |
| Lowry Construction Recent nearby: 430 Laverne Av (Jun 19, 2018) | New garage / accessory structure | 2 in ½ mi | $1,100,000 | 0 vs 0 prior |
| Vida Building Recent nearby: 455 Panoramic Hwy (Nov 7, 2023) | Remodel / interior alteration | 2 in ½ mi | $668,420 | 3 vs 2 prior |
| Osmun Construction Recent nearby: 620 Douglas Dr (Aug 12, 2021) | Addition (adds square footage) | 2 in ½ mi | $475,000 | 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 |
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.