910 Union Street (Park Union)
910 Union Street, Brooklyn, NY 11215
BBL 3010667503 · BIN 3024701
- Year built
- 1931
- Type
- Condominium
- Units
- 15
- Floors
- 7
- Landmark
- No
Own an apartment here? See what it would sell for.
A Private Pricing Opinion — what your apartment at Park Union, per listing records would likely sell for today, what it costs to sell, and what you’d walk away with — reviewed personally against condition, exposures, renovation quality, and the competition actually on the market.
910 Union Street is one of the properties near Grand Army Plaza that were left outside the Park Slope Historic District. That is how the project happened: a low 1930s clubhouse was enlarged to seven stories without Landmarks review. The building was sold for redevelopment in 2008. The first developer stalled, and American Development Group took over in 2010. The addition topped out in 2012, and the condominium was declared in May 2013. All fifteen residences closed that summer to fifteen separate buyers.
The design choice was to make the old building part of the new one. Press accounts at the time described the limestone entry and cornice as kept and the new floors as brick color-matched to the original. The developer publicly floated seeking landmark status after completion, but LPC's database shows none. For a buyer, that means no Landmarks review on the outside, and no Landmarks protection against change next door either.
Architecture and unit composition
The building is seven stories on a 59-by-95-foot lot, with the old base carrying the ground floor and the new brick floors above. There are two apartments on most floors, an A line and a B line. On floors 3 through 7 these run about 1,430 to 1,535 square feet. The second floor has three smaller units of about 735 to 1,220 square feet. On the ground floor, Unit 1A is the largest residence at about 1,905 square feet, and 1B is the smallest at about 785.
The commercial unit is about 5,025 square feet at the base and is separately owned. Commercial real estate press reported in 2023 that a preschool operator was taking the space. Ask for the commercial unit's share of common charges, what the declaration says about its use, and how its entrance and hours sit alongside the residential lobby.
Amenities and outdoor space are not in the city record; confirm them at offer stage.
Building operations
This is a fifteen-residence elevator condominium without full-time lobby staff documented in the public record. Confirm the staffing model with the managing agent. The 2017 amended declaration has not been reviewed here. Read it for any change to unit boundaries, common interests or the commercial unit's rights.
Policy framework
421-a, in plain terms. 421-a is a New York City program that exempts the added value from new construction, or from a qualifying conversion, from property tax for a fixed term. The Department of Finance records exemption code 5118, 421-a 15-year with cap, benefit start 2014, on every residential lot and on the commercial unit. "Cap" means the exempt amount per unit is limited. Under the program's 15-year schedule the benefit runs at full value for its first years, then steps down in 20-percent increments and ends after the 2028/29 tax year. It is in the phase-down now. The 2027/28 roll shows the exempt amount per unit down from 2026/27. Confirm the current percentage on the unit's Notice of Property Value.
What that means for a buyer. Each remaining year raises the tax bill. From 2029/30 every unit pays full tax. Anyone holding past 2029 should underwrite the full-tax number.
No J-51, no affordable units. Despite the building's age, no J-51 benefit appears on any roll. ACRIS shows no regulatory agreement recorded against the condominium lots.
Condominium mechanics. Apartments convey by deed on separate tax lots. The 2013 declaration and 2017 amendment set leasing, pets and any right of first refusal. Confirm them with the managing agent.
Recent sales
910 Union trades at the upper end of Park Slope's small-condominium market, priced per square foot against park-block and Grand Army Plaza product: the large conversion at 1 Prospect Park West, the plaza's postwar co-ops, and the newer condominiums on the Prospect Heights side. Resales have been steady since the 2013 sellout, a handful a year at most. The A- and B-line units on the upper floors set the building's price level. The second-floor units and 1B trade at the smaller end of the market. Unit-level transaction history is maintained in The Roebling Research Library and shared with clients during diligence.
The retrade record
Lines that have traded more than once in the public record — the building’s appreciation arc, apartment by apartment.
Recent closings at this building, sourced from NYC Department of Finance records. Apartment-level detail (line, condition, asking-price context) verified upon consultation request.
| Date | Unit | Price |
|---|---|---|
| Jun 15, 2026 | 4B | $2,815,000 |
| May 19, 2026 | 5B | $2,825,000 |
| Dec 22, 2025 | 1B | $930,000 |
| Aug 26, 2025 | 3B | $2,575,000 |
| Nov 27, 2023 | 1B | $865,000 |
| May 31, 2023 | 4A | $2,510,000 |
Full closing history with price-per-square-foot over time, the complete retrade record, and every line that has traded.
Sales sourced from NYC Department of Finance recorded transfers (BBL 3-01066-7503) and verified listing data. Apartment-level facts (line, condition, asking-price context) curated and cross-verified by The Roebling Team research desk. Not all transactions cross-verify with ACRIS records — sponsor and LLC purchases sometimes record at stipulated values rather than market price.
At the recent median sale of $2.81M (4 sales since 2024), a buyer putting 25% down would pay about $114,181 to close, or 4.1% of the price.
- Mansion tax: $35,188
- Mortgage recording tax: $40,642
- Title insurance: $12,667
- Attorneys, lender, building fees, reserves and filings: $25,684
Assumes a resale (the seller pays transfer taxes), a $4,500 attorney fee and a mortgage on the rest.
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What to know if you’re buying
Model the tax bill to 2029/30. The 421-a is in its last phase-down years. Today's bill understates what every owner will pay within a few years.
Understand the commercial unit. It is one of sixteen lots but about a fifth of the building's floor area. Its use, its share of charges and its tenant affect life in the building.
No landmark cover. The building is outside the district, and so is the corner lot next door.
Comparable buildings
- 1 Prospect Park West — the 2019 clubhouse conversion on the corner of this block
- 1 Grand Army Plaza — the glass condominium across the plaza, the new-construction alternative
- 9 Prospect Park West — the 1929 park-front cooperative a block south
- 309 2nd Street — another conversion with a vertical enlargement, on the Fourth Avenue side of the Slope
- 11 Sterling Place — a 1986 conversion of a prewar industrial building near the plaza
- 145 Park Place — a theater-building conversion with commercial units at its base
- 939 Union Street — a 2003–04 condominium on Union Street's park block
- 759 President Street — an institutional-to-residential conversion, run as a co-op
More Park Slope buildings
- 9 Prospect Park West — 1928 co-op
- 90 Eighth Avenue — 1927 co-op by Sugarman & Berger
- 904 Union Street — 1910 co-op
- Baltic Park Slope (613 Baltic Street) — 2016 condominium
- The Park Pavilion, 372 15th Street — 2005 condominium
- The Shinnecock, 939 Union Street — 2003 condominium
The neighborhood
For the full neighborhood — its buildings, character, and market — read The Roebling Team Guide to Park Slope.
How to read the facts on this page. Items attributed to an offering plan describe the building as it was offered at that filing — unit mix, square footage, the amenity program as planned. They are not a statement about how the building operates today. Tax and compliance figures are sourced separately to current City records and carry their own dates. House rules, staffing and fee policy can change by board resolution without any public filing: treat every policy line here as a starting point for diligence and confirm it with the managing agent. Where this page compares one building or neighborhood to another, that is our analysis of the recorded record — it names the measure, the period and the sample it rests on, and it is an observation about medians rather than a prediction about any particular apartment.
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