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423-431 Union St

Telegraph Hill, SF 94133 0115054 6 units · 3 fl · 1906

This building has significantly more problems than most nearby buildings. A handful of unresolved issues. Worth a careful walk-through and pointed questions.

NOVs (7y) vs. neighborhood
Compared to a typical building in Telegraph Hill
At or below average
avg 1.2
1
FewerMore

This building has 1 novs (7y), at or below the Telegraph Hill average of 1.2.

Rent & eviction protection

Is 423-431 Union 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.

Built before 1979
Built 1906
2 or more units
6 units
Property type
Multi-Family Residential
Zoning
RH3
Likely rent-controlled. Building age and unit count suggest this property falls under San Francisco's Rent Ordinance.

Based on SF Assessor records. Not legal advice — confirm with the SF Rent Board.

Building characteristics
Units6
Floors3
Year built1906
Total area6,355 sq ft
Property typeMulti-Family Residential
Tax statusNone
Blocklot0115054
Ownership

Registered owner per SF Assessor-Recorder (secured roll).

Owner name
Gilbert Fmly 1991 Tr
Mailing address
Gilbert William F & Lee Ann Po Box 620099 Woodside CA 94062
Last sale
021618

Landlord portfolio

Other SF properties this owner holds, with risk grades for each.

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Multiple entrances & addresses

Included addresses

All street addresses sharing this blocklot that are covered by this report.

423 Union St, San Francisco, CA 94133
429 Union St, San Francisco, CA 94133
431 Union St, San Francisco, CA 94133
425 Union St, San Francisco, CA 94133
427 Union St, San Francisco, CA 94133
Augrented Insights
Initial analysis

The building at 423-431 Union Street in Telegraph Hill is a three-story multi-family residential structure built in 1906, currently owned by the Gilbert Family 1991 Trust. The property, originally consisting of 6 units, has undergone significant modernization and safety improvements over recent years, including comprehensive fire safety upgrades. Most notably, in 2024, the building received a new fire alarm system and underwent a major fire sprinkler installation project covering the basement and new ADUs on the first floor. The building is in compliance with the San Francisco Mandatory Soft Story Retrofit Program, having completed required seismic upgrades in 2024, which included soft-story retrofit work at the basement level and ADA improvements to the first-floor retail space. Recent improvements also include HVAC upgrades, with the installation of new high-efficiency furnaces and heat pumps throughout the building.

The property has experienced some maintenance and safety issues in the past, including lead paint concerns documented in complaints from 2013-2014, which were subsequently addressed. A 2022 complaint regarding garbage area access was resolved, and there have been several 311 calls regarding debris and cleaning issues near the property, most recently in 2024. The building underwent substantial renovation work in 2020-2023, including the removal of non-permitted units and conversion of commercial space into additional residential units, bringing the total to 8 residential units. This extensive work also incorporated new plumbing and electrical systems, with permits showing ongoing maintenance and system upgrades throughout 2023-2024. The most recent inspections and permits indicate that the property is actively maintaining compliance with current building codes and safety requirements, with all major outstanding issues having been addressed or resolved.

AI-generated · may contain errors · check the source data tables below

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Risk rating

How 423-431 Union 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

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.

Neighborhood percentile
10th percentile

Out of 684 buildings in this neighborhood, 616 are predicted to be safer.

RiskiestSafest
Predicted 12-month outcome
37%
No DBI
violation
63%
DBI violation
likely
Model explanation

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.

Number of units

The number of units affects how the model reads complaint and violation totals — more units means more potential sources.

Building size

Total floor area — a proxy for building scale and the number of systems (plumbing, electrical, HVAC) that can fail.

Director's hearings (past 7 years)

Director's hearings are escalated enforcement actions for buildings that haven't resolved violations — a serious signal.

12-Month severity forecast
No violation 39.5%
Moderate concern 53.0%
Severe concern 7.4%
Estimated probability of receiving a DBI Notice of Violation in the next 12 months at each severity level. Model: full_hgb_balanced.
Apartment reviews

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The story over time

423-431 Union St event timeline

Violations, complaints, fire incidents, permits, and buyouts — most recent records in order.

2026
311 Request Jan 25
Other illegal parking
Parking Enforcement
311 RequestJan 02
Garbage and debris

See all 20 events

Full history back to 2020 — violations, complaints, permits, buyouts, and fire incidents.

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Every record we have

Full data for 423-431 Union St apartments

13 SF public datasets for this parcel — permits, violations, complaints, fire records, 311 calls, planning records, and buyouts.

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Cancel anytime · Data sourced from SF Open Data, DBI, SFFD, SF Rent Board & Planning

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