San Rafael 94903 · Marinwood · APN 164-521-20 · Unincorporated Marin
Zoned RMP-6 in Unincorporated Marin with likely ministerial ADU eligibility and mapped CAL FIRE moderate fire hazard severity zone (local responsibility area) due diligence; benchmark value $1,255,000 ($1,104,000–$1,406,000).
Zone RMP-6 allows residential use qualifying for ministerial ADU review under state law (2 ADU permits permitted within ¼ mile in 36 months).
Source: Unincorporated Marin zoning · CA Gov. Code 66314
On-parcel permit history is indexed through Oct 4, 2023, 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)
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)
Automated synthesis of indexed municipal, county, state, and federal public records — informational context only, not a formal appraisal, survey, or legal/tax determination.
$1,255,000
Benchmark range: $1,104,000 – $1,406,000
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: 125 new homes (0.32 mi N, entitled). 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 (~$1,240/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: 9 permitted, 125 proposed or in review (124 of them deed-restricted affordable).
11 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.
530 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 RMP-6 as multifamily 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 10.1 yr (first record Oct 17, 2016), with no completion or new permit record in 9.7 yr. · 1 unit · $185,000 declared valuation
Permit issued and active for 8.2 yr (first record Sep 10, 2018), with no completion or new permit record in 8.2 yr. · $9,500 declared valuation
In "Applied" for 5.5 yr (since Apr 29, 2021), with no new permit record in 5.5 yr. · 1 unit · $27,000 declared valuation
Permit issued and active for 4.5 yr (first record May 13, 2022), with no completion or new permit record in 4.5 yr. · $275,000 declared valuation
In "Applied" for 3.9 yr (since Dec 14, 2022), with no new permit record in 3.9 yr. · $35,000,000 declared valuation
In "Applied" for 3.1 yr (since Oct 20, 2023), with no new permit record in 3.1 yr. · 1 unit · $559,117 declared valuation
Nearby remodel / interior alteration (515 Pinewood Dr): First appeared in published agency feed
Record 182948 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby remodel / interior alteration (515 Pinewood Dr): No longer present in latest agency feed
Record 94393 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby roof replacement (2510 Opalstone Ter): First appeared in published agency feed
Record B49084 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby roof replacement (155 Blackstone Dr): First appeared in published agency feed
Record B49081 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (2618 Las Gallinas Ave): First appeared in published agency feed
Record B49057 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby addition (adds square footage) (2195 Las Gallinas Ave): Contractor changed from (blank) to BOLT DOWN THE BAY AREA
Record 182899 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby windows / doors / siding (435 Pinewood Dr): First appeared in published agency feed
Record B49047 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby plumbing / water heater / sewer (320 Quietwood Dr): First appeared in published agency feed
Record B49024 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby roof replacement (245 Cobblestone Dr): First appeared in published agency feed
Record B49009 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby addition (adds square footage) (2545 Opalstone Ter): First appeared in published agency feed
Record 94632 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby addition (adds square footage) (2195 Las Gallinas Ave): First appeared in published agency feed
Record 182899 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby windows / doors / siding (255 Flagstone Ter): First appeared in published agency feed
Record B48984 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby ev charger (475 Pinewood Dr): First appeared in published agency feed
Record B48993 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby other (475 Pinewood Dr): First appeared in published agency feed
Record B48992 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby addition (adds square footage) (2195 Las Gallinas Ave): No longer present in latest agency feed
Record 94431 · 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 →In "Entitled" for 23 mo (since Dec 6, 2024), exceeding the 292d median and 313d 90th percentile for new multifamily / condos / mixed-use permits in Unincorporated Marin (n=21). High-impact scale (125 housing units, 124 deed-restricted affordable across 0 permits).
In "Applied" for 3 yr (since Oct 31, 2023), 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, $2,993,758 declared valuation across 1 permit).
In "Applied" for 3 yr (since Nov 28, 2023), 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, $56,632,994 declared valuation across 1 permit).
In "Applied" for 3 yr (since Nov 28, 2023), 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, $55,415,888 declared valuation across 1 permit).
In "Applied" for 3 yr (since Nov 28, 2023), 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, $55,415,888 declared valuation across 1 permit).
Active in "Applied" for 3.9 yr (first record Dec 14, 2022) with no new permit activity recorded in 3.9 yr. High-impact scale ($35,000,000 declared valuation across 2 permits).
Substantial improvements (additions, interior remodels, ADUs, commercial TI, and new builds) across 1,737 parcels
−23.1% YoY
City baseline: 16.4 / 1k
23 in trailing 24m
Includes 15 ADUs
| Builder / contractor | Primary specialty | Here / ½ mi | ½ mi valuation | Citywide 24m trend |
|---|---|---|---|---|
| High Wire Electric | Electrical / panel | 1 on parcel1 in ½ mi | $3,000 | 0 vs 0 prior |
| Owner Builder Recent nearby: 155 Marinwood Ave (Oct 22, 2026) | Remodel / interior alteration | 39 in ½ mi | $2,305,456 | 226 vs 240 prior−6% |
| Owner Recent nearby: 2 Erin Dr (Feb 7, 2025) | Remodel / interior alteration |
| 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 94903
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 ($12,550/yr) + local voter-approved bond debt ($1,883/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.
−$55,557/yr
Cash needed: $276,100
NOI: $20,595/yr
P&I: $6,346/mo
For $0/mo net cash flow
At $4,175/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 | $3,841/mo | −$5,109/mo | -22.2% | $10,973/mo | −$5,068/mo |
| Base (your inputs) | Your entered assumptions, 3.0%/yr rent growth | $4,175/mo | −$4,630/mo | -20.1% | $10,157/mo | −$4,352/mo |
| Optimistic (cap-limited) | +6% starting rent, 3% vacancy, 4.5%/yr rent growth (capped by AB 1482 ceiling of 8.6%/yr) | $4,426/mo | −$4,354/mo | -18.9% | $9,921/mo | −$3,807/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 obsolete 100amp underground electrical service — Service Upgrade
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
0.01 acres
Assessor's classification for assessment purposes. This is not zoning.
40 BLACKSTONE DR
Source: County of Marin GIS (MarinMap), Parcels · Geography: parcel · Retrieved Nov 13, 2026
Search by parcel number 164-521-20. Assessed value is not market value.
Search by parcel number 164-521-20 (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.
| 28 in ½ mi |
| $1,468,687 |
| 25 vs 15 prior+67% |
| Haven Construction Recent nearby: 19 Erin Dr & 19a - Lot 5 (May 2, 2025) | Accessory dwelling unit (new or conversion) | 7 in ½ mi | $3,773,930 | 14 vs 3 prior |
| Mastec Communicaitons Group Recent nearby: 155 Marinwood Ave Bldg A (121 (Jun 23, 2026) | New multifamily / condos / mixed-use | 5 in ½ mi | $175,000 | 10 vs 0 prior |
| Gelardi Construction Recent nearby: 417 Miller Creek Rd (Aug 13, 2024) | Addition (adds square footage) | 4 in ½ mi | $842,420 | 0 vs 1 prior |
| Marin Kitchen Works Recent nearby: 345 Peachstone Ter (Jan 25, 2022) | Remodel / interior alteration | 4 in ½ mi | $125,000 | 0 vs 2 prior |
| Kl Construction Recent nearby: 209 Blackstone Dr (Jun 13, 2025) | Addition (adds square footage) | 3 in ½ mi | $862,000 | 2 vs 0 prior |
| Hsc Services Recent nearby: 377 Quietwood Dr (May 4, 2022) | Remodel / interior alteration | 3 in ½ mi | $784,500 | 1 vs 0 prior |
| Swan Pools Recent nearby: 2750 Heatherstone Dr (Aug 2, 2016) | Pool / spa | 3 in ½ mi | $114,500 | 1 vs 4 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) |
| Electrical / panelOn this parcel | 3,019 | 0d | 0d | 0d | 2d | 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.