5806 21st Avenue, Brooklyn
Four-family · built c. 1931 · Block 5507, Lot 38.
Building permits
- Alteration, filed Aug 15, 2025, estimated cost $9K, described as “Plumbing work as per plan.”
- Alteration, filed May 27, 2025, estimated cost $12K, described as “Proposed installation of temporary pipe scaffold as per plans. Work shall comply with chapter #33 of the NYC building code. No change in use, occupancy, or egress under this application.”
- Alteration, filed May 27, 2025, estimated cost $5K, described as “Proposed installation of heavy duty sidewalk shed as per plans. Live load 300 lbs per square feet. Sidewalk shed shall comply with chapter #33 of the NYC building code. No change in use, occupancy, or egress under this application.”
- Alteration, filed Jun 17, 2024, estimated cost $808K, described as “Adding a new story to an existing 2 story, 4 family dwelling. Work as per plan.”
- Alteration, filed May 29, 2024, estimated cost $242K, described as “Interior removal, work only. No change of bulk, egress or use.”
Property taxes
- Assessment
- $398,250
- 2026–27 tax
- $14,712
- Market value (city estimate)
- $885,000
- Taxable value
- $118,275
- Assessed land
- $95,400
- Assessed improvements
- $302,850
Zoning
R5: floor area ratio 1.32 built, 1.50 allowed by base zoning.
Flood zone
Current FEMA flood map: zone X, minimal flood hazard.