San Rafael 94903 · Marinwood · APN 164-142-02 · Unincorporated Marin
Zoned R1 in Unincorporated Marin with likely ADU & SB 9 infill eligibility and zero mapped flood, fire, or fault hazard overlaps; benchmark value $1,531,000 ($1,347,000–$1,715,000).
Zoned R1 supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 7,797 sq ft lot. Local precedent is active with 3 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 (3 total permits, latest Sep 5, 2025).
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.
$1,531,000
Benchmark range: $1,347,000 – $1,715,000
Accessory dwelling unit at 287 Blackstone Dr: Active in "Issued" for 19 mo (first record Apr 23, 2025) with no new permit activity recorded in 14 mo.
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (review-time benchmark)
Closest lead: 125 new homes (180 ft NW, 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 (~$1,505/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: 4 permitted, 125 proposed or in review (124 of them deed-restricted affordable).
6 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.
460 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 8.7 yr (first record Mar 15, 2018), with no completion or new permit record in 8.6 yr. · $100 declared valuation
Permit issued and active for 8.4 yr (first record Jun 12, 2018), with no completion or new permit record in 7.7 yr. · 1 unit · $180,000 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 "Entitled" for 23 mo (since Dec 6, 2024), with no new permit record in 23 mo. · 125 units
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 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 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 solar / battery storage (175 Marinwood Ave (Bldg A)): First appeared in published agency feed
Record 94605 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby solar / battery storage (175 Marinwood Ave (Bldg B)): First appeared in published agency feed
Record 94606 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby solar / battery storage (175 Marinwood Ave (Bldg C)): First appeared in published agency feed
Record 94607 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby solar / battery storage (175 Marinwood Ave (Bldg D)): First appeared in published agency feed
Record 94608 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby hvac / heat pump (95 Windstone Dr): First appeared in published agency feed
Record B48894 · Detected between snapshots
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · Snapshot diff within ½ mile
Nearby new garage / accessory structure (155 Marinwood Ave): Issued date changed from 2026-09-21 to 2026-10-22
Record 182601 · 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 $1,200,587 in September 2025 to $1,250,063 in September 2026.
Source: Zillow Home Value Index (ZHVI) · Data provided by Zillow · Geography: ZIP 94903 (not a parcel appraisal)
2535 Opalstone Ter ( A D U 2535 A) · 1 unit · $116,456 valuation
Records span Mar 13, 2026 to Sep 30, 2026 (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 "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).
Active in "Issued" for 19 mo (first record Apr 23, 2025) with no new permit activity recorded in 14 mo.
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).
In "Applied" for 5.5 yr (since Apr 29, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
Active in "Issued" for 19 mo (first record Apr 18, 2025) with no new permit activity recorded in 14 mo.
Active in "Issued" for 8.7 yr (first record Mar 15, 2018) with no new permit activity recorded in 8.6 yr.
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 |
|---|---|---|---|---|
| Filshie Enterprises | Accessory dwelling unit (new or conversion) | 1 on parcel1 in ½ mi | $500,000 | 0 vs 0 prior |
| Allen Heating And Sheet Metal | HVAC / heat pump | 1 on parcel1 in ½ mi | $10,864 | 0 vs 0 prior |
| Integrity Electric | Electrical / panel | 1 on parcel1 in ½ mi | $6,300 |
| 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 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 ($15,300/yr) + local voter-approved bond debt ($2,295/yr) + fixed direct levies/Mello-Roos ($450/yr).
Insurance & hazard context:
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.
−$74,086/yr
Cash needed: $336,600
NOI: $18,752/yr
P&I: $7,737/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 | −$6,654/mo | -23.7% | $13,129/mo | −$6,623/mo |
| Base (your inputs) | Your entered assumptions, 3.0%/yr rent growth | $4,175/mo | −$6,174/mo | -22.0% | $12,152/mo | −$5,906/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 | −$5,898/mo | -21.0% | $11,869/mo | −$5,361/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.
Issued1 unitsApr 23, 2025 – Sep 5, 2025
We group related permits and State housing reports into projects. That grouping is our inference, not an official record.
Whole House Remodel; Kitchen Addition; (N) Attached Rear Ground Flr J A D U; Covered Entry Porch
Service Upgrade To 200 Amp, Circuit For A/C System By Others, Can Lights In Lvg Rm
Rplc Heating And A/C***Expired
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 |
|---|---|---|---|---|---|---|
| 2025 | —(179994) | ADU · Renter | — | 1 (Sep 5, 2025) | — | — |
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
0.18 acres
Assessor's classification for assessment purposes. This is not zoning.
287 BLACKSTONE DR
Source: County of Marin GIS (MarinMap), Parcels · Geography: parcel · Retrieved Nov 13, 2026
Search by parcel number 164-142-02. Assessed value is not market value.
Search by parcel number 164-142-02 (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: 155 Marinwood Ave (Oct 22, 2026) | Remodel / interior alteration | 41 in ½ mi | $2,542,556 | 226 vs 240 prior−6% |
| Owner Recent nearby: 435 Peachstone Ter (Sep 6, 2024) | Remodel / interior alteration | 23 in ½ mi | $775,187 | 25 vs 15 prior+67% |
| Mastec Communicaitons Group Recent nearby: 155 Marinwood Ave Bldg B (121 (Jun 23, 2026) | New multifamily / condos / mixed-use | 5 in ½ mi | $175,000 | 10 vs 0 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 |
| Swan Pools Recent nearby: 2750 Heatherstone Dr (Aug 2, 2016) | Pool / spa | 3 in ½ mi | $114,500 | 1 vs 4 prior |
| Rebath By Schicker Recent nearby: 20 Miller Ranch Ct (Jan 14, 2019) | Remodel / interior alteration | 3 in ½ mi | $53,000 | 0 vs 1 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) |
| HVAC / heat pumpOn this parcel | 2,946 | 0d | 0d | 0d | 0d | 0d |
| 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.