621 Union Avenue, Brooklyn
Apartment building · 5 units · built c. 1910 · Block 2292, Lot 18.
Building permits
- Alteration, filed Sep 9, 2025, estimated cost $1K, described as “Installation of temporary heavy duty sidewalk shed as per plans. No change in use, egress or occupancy. Sidewalk shed shall comply with chapter #33 of 2022 the NYC building code. Live load 300PSF.”
- Major Renovation — Multi-Family, filed Aug 5, 2024, estimated cost $2.4M, 9 units in all, 6 stories, described as “Vertical extension of existing 2 story and converted to 6 story mixed use building, commercial and 9 dwelling units, obtain new c of o.”
- Alteration, filed May 17, 2022, estimated cost $33K, described as “Modernize the front facade and providing a facelift to the front facade to make it fit into the surrounding neighborhood better.”
Property taxes
- Assessment
- $864,000
- 2026–27 tax
- $11,724
- Market value (city estimate)
- $1,920,000
- Taxable value
- $94,253
- Assessed land
- $202,950
- Assessed improvements
- $661,050
Zoning
M1-2/R6A: floor area ratio 1.62 built, 3.00 allowed by base zoning.
Flood zone
Current FEMA flood map: zone AE, high risk: a 1% chance of flooding each year, base flood elevation 10 ft (NGVD29). FEMA’s preliminary map: zone X, moderate risk: a 0.2% chance of flooding each year.
Recent sales
- Apr 14, 2022: $4,501,000
Open-market sales since 2016, from the Department of Finance’s sales files.