509-511 21St Ave
This building has a higher-than-average number of open problems nearby. Few open issues; problems get fixed quickly. A reasonable bet for a smooth tenancy.
This building has 0 novs (7y), at or below the Central Richmond average of 0.5.
Is 509-511 21St Ave rent-controlled?
San Francisco's Rent Ordinance caps rent increases and provides eviction protection for most residential units built before 1979 with 2+ units. Here's how this building scores.
Based on SF Assessor records. Not legal advice — confirm with the SF Rent Board.
| Units | 2 |
|---|---|
| Floors | 2 |
| Year built | 1922 |
| Total area | 2,820 sq ft |
| Property type | Multi-Family Residential |
| Tax status | None |
| Blocklot | 1564001B |
Registered owner per SF Assessor-Recorder (secured roll).
Landlord portfolio
Other SF properties this owner holds, with risk grades for each.
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All street addresses sharing this blocklot that are covered by this report.
The two-unit residential building at 509-511 21st Avenue in the Central Richmond neighborhood is a two-story flats and duplex structure built in 1922, currently owned by Benjamin C. Owyoung. The building has undergone several significant improvements over the years, with the most recent major work being the installation of new fiber cement siding at the rear of the building in 2015, a project that cost $5,000. Other notable improvements include a garage door replacement in 2007 ($750), a complete reroofing in 2007 ($5,000), and substantial electrical upgrades in 2003-2004, including the installation of a new electrical panel and additional circuits throughout the unit. A possible illegal basement unit was reported in 1997 but was resolved by January 1998.
AI-generated · may contain errors · check the source data tables below
How 509-511 21St Ave's risk score is calculated
We trained a model on 7 years of SF DBI inspection data — notice of violation filings, complaint history, and owner track records. It estimates the probability that DBI inspectors will issue a Notice of Violation at this address in the next 12 months. Lower % = safer.
What the score means for you
Grade A–B — Low risk
DBI rarely finds violations here. Strong maintenance history and a clean complaint record.
Grade C — Moderate risk
Some past violations or complaints on record. Worth asking the landlord about any open issues before signing.
Grade D–F — High risk
Elevated violation and complaint history. DBI has found issues here before and is statistically likely to again.
Out of 2250 buildings in this neighborhood, 855 are predicted to be safer.
violation
likely
What's driving this score
The three data points that most influenced this building's risk rating — ranked by the weight the model placed on each one.
509-511 21St Ave apartment reviews
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509-511 21St Ave event timeline
Violations, complaints, fire incidents, permits, and buyouts — most recent records in order.
See all 1 events
Full history back to 2025 — violations, complaints, permits, buyouts, and fire incidents.
Unlock complete timelineFull data for 509-511 21St Ave apartments
13 SF public datasets for this parcel — permits, violations, complaints, fire records, 311 calls, planning records, and buyouts.
What this is
Permits issued by the SF Department of Building Inspection for new construction, alterations, and repairs. Includes estimated cost and current permit status.
| Permit # | Description | Cost | Filed | Status |
|---|---|---|---|---|
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What this is
Plumbing permit applications filed with the SF Department of Building Inspection. Covers plumbing installation, repair, and replacement work.
| Permit # | Description | Filed | Status |
|---|---|---|---|
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What this is
Electrical permit applications filed with the SF Department of Building Inspection. Covers electrical wiring, panel upgrades, and related work.
| Permit # | Description | Filed | Status |
|---|---|---|---|
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What this is
Notices of Violation issued by the SF Department of Building Inspection for code violations. Unresolved notices can escalate to legal action.
| Date Filed | Complaint # | Description | Item | Category | Status |
|---|---|---|---|---|---|
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What this is
Complaints filed with the SF Department of Building Inspection about code violations. Tracks the complaint lifecycle from filing through abatement or referral.
| Complaint # | Date Filed | Date Abated | Division | Status | Description |
|---|---|---|---|---|---|
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What this is
Planning Department project entitlements — discretionary review, conditional use, variances, and environmental review for this parcel.
| Address | Opened | Closed | Status | Description | Applicant |
|---|---|---|---|---|---|
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What this is
Planning Department administrative and compliance records that are not full project entitlements — pre-application meetings, code violations, and referrals.
| Address | Opened | Closed | Status | Description | Applicant |
|---|---|---|---|---|---|
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What this is
SFFD fire incidents geo-joined to this parcel. Covers structure fires, alarms, and emergency responses with injury and fatality counts.
| Date | Situation | Civilian Injuries | Civilian Fatalities |
|---|---|---|---|
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What this is
Fire code violations issued by the SFFD. Tracks corrective actions required and resolution status for fire safety code enforcement.
| Violation Date | Description | Corrective Action | Status | Close Date |
|---|---|---|---|---|
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What this is
Fire code complaints received by the SF Fire Department geo-joined to this parcel. Includes complaint type, disposition, and outcome.
| Received | Description | Disposition Date | Disposition |
|---|---|---|---|
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What this is
SF 311 service requests geo-joined to this parcel. Includes maintenance complaints, street/sidewalk issues, and quality-of-life requests.
| Opened | Type | Agency | Category | Details | Status |
|---|---|---|---|---|---|
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What this is
Buildings subject to SF's mandatory soft-story seismic retrofit program. Unreinforced multi-story wood-frame buildings must meet compliance tiers.
| Tier | Status |
|---|---|
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What this is
Tenant buyout (Ellis Act pre-cursor) agreements recorded with the SF Rent Board. Tracks amounts paid to tenants to vacate rent-controlled units.
| Disclosure Date | Buyout Date | Amount | Tenants |
|---|---|---|---|
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