635-639 Mason St
A handful of records on file over the last seven years, and our model puts this building at a low risk of further maintenance problems in the next 12 months. A few records worth reading before you sign. Check whether they were closed out, and ask what was actually fixed.
This building has 2 novs (7y), at or below the Union Square average of 7.1.
Is 635-639 Mason St 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.
California Tenant Protection Act of 2019
Even when a building isn't covered by local rent stabilization, the statewide Tenant Protection Act (AB 1482) may still apply. It caps annual rent increases and requires the landlord to state a legal reason to end most tenancies.
AB 1482 does not apply to single-family homes and condos unless owned by a corporation, REIT, or an LLC with a corporate member; to owner-occupied duplexes; or to deed-restricted affordable housing. The Act is in effect until January 1, 2030. Not legal advice — see the California landlord–tenant guide.
| Units | 4 |
|---|---|
| Floors | 3 |
| Year built | 1907 |
| Total area | 6,332 sq ft |
| Property type | Multi-Family Residential |
| Tax status | None |
| Blocklot | 0283003 |
Registered owner per SF Assessor-Recorder (secured roll).
Landlord portfolio
Other SF properties this owner holds, with a risk rating for each.
Unlock complete reportIncluded addresses
All street addresses sharing this blocklot that are covered by this report.
The 4-unit, 3-story multi-family residential building at 635-639 Mason Street in Union Square, owned by Opmc - 635 Mason Llc, has shown a consistent pattern of maintenance and safety compliance issues over its history. Built in 1907, the building experienced significant water damage in 2007 requiring $10,000 in drywall repairs in a storage area. More concerning is the building's fire safety record, with multiple violations and complaints regarding sprinkler systems, alarm systems, and blocked exits between 2019 and 2023, though most were promptly corrected or found to have no merit. A cluster of violations was documented in September 2000, including flammable storage, lack of a utility shut-off tool, an expired hallway fire extinguisher, and door closure issues, though these were abated by October 2000. The building underwent several improvements in 1997, including the installation of two skylights in unit #639's kitchen and adjustments to a skylight's placement.
AI-generated · may contain errors · check the source data tables below
How 635-639 Mason St'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
Lower risk — safer than most nearby
DBI rarely finds violations here. Strong maintenance history and a clean complaint record.
Typical — about average for the neighborhood
Some past violations or complaints on record. Worth asking the landlord about any open issues before signing.
Higher risk — riskier than most nearby
Elevated violation and complaint history. DBI has found issues here before and is statistically likely to again.
Out of 38 buildings in this neighborhood, 2 are predicted to be safer. The band is relative to this neighborhood, so a share of every neighborhood falls in each colour.
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.
635-639 Mason St apartment reviews
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635-639 Mason St event timeline
Violations, complaints, fire incidents, permits, and buyouts — most recent records in order.
See all 2 events
Full history back to 2023 — violations, complaints, permits, buyouts, and fire incidents.
Unlock complete timelineFull data for 635-639 Mason St 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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How 635-639 Mason St compares to the neighborhood
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