910 Union Street (Park Union)
910 Union Street, Brooklyn, NY 11215
Park Slope, Brooklyn
BBL 3010667503 · BIN 3024701
- Year built
- 1931
- Type
- Condominium
- Units
- 15
- Floors
- 7
- Landmark status
- Requires confirmation
- City records and our profile differ. Confirm with building management.
- Doorman
- Full-time doorman
Park Union, per listing records sales history: 28 recorded sales
Every recorded sale at this building, 2013–2026
Price-per-square-foot over time, the line- and floor-premium curves, and every recorded sale.
- Median $/sf, 2026 to date
- $1,884
- floor-adjusted, 2 sales
- Listing discount
- 0.0%
- Recorded sales
- 28
- On record
- 2013–2026
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. Because the lot is outside the district, the enlargement of a low 1930s clubhouse to seven stories needed no 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 about 786; the smallest residence on the Department of Finance roll is 2C, at about 735. These are tax-roll gross areas; confirm interior square footage from the offering plan or a measured plan.
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, counting from the recorded start, ends after the 2028/29 tax year; confirm the final year on the unit's official 421-a schedule. 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.
Application and transaction fees
Fees below are from building management's published schedule, as of August 2026. They are shown as published, item by item; no total is added because the total depends on the transaction. Deposits are listed apart from nonrefundable charges.
Purchase
7 items
Fees and charges
| Item | Paid by | When | Amount | Refundable |
|---|---|---|---|---|
| Application Processing Fee | Paid by Buyer | When With the application | Amount $700 | Refundable Non-refundable |
| Credit Report FeePer applicant | Paid by Buyer | When With the application | Amount $200 per applicant | Refundable Non-refundable |
| Waiver of Right of First Refusal | Paid by Seller | When With the application | Amount $350 | Refundable Not stated |
| Management Closing Fee | Paid by Buyer | When At closing | Amount $275 | Refundable Not stated |
| Management Closing Fee | Paid by Seller | When At closing | Amount $275 | Refundable Not stated |
Deposits
| Item | Paid by | When | Amount | Refundable |
|---|---|---|---|---|
| Move In Deposit | Paid by Buyer | When With the application | Amount $500 | Refundable Refundable |
| Move Out Deposit | Paid by Seller | When With the application | Amount $500 | Refundable Refundable |
Rental or lease
5 items
Fees and charges
| Item | Paid by | When | Amount | Refundable |
|---|---|---|---|---|
| Waiver of Right of First Refusal | Paid by Landlord | When With the application | Amount $350 | Refundable Not stated |
| Application Processing Fee | Paid by Tenant | When With the application | Amount $350 | Refundable Non-refundable |
Deposits
| Item | Paid by | When | Amount | Refundable |
|---|---|---|---|---|
| Move Out Deposit | Paid by Landlord | When With the application | Amount $500 | Refundable Refundable |
| Move In Deposit | Paid by Tenant | When With the application | Amount $500 | Refundable Refundable |
Lease renewal
Fees and charges
| Item | Paid by | When | Amount | Refundable |
|---|---|---|---|---|
| Application Processing Fee | Paid by Tenant | When With the application | Amount $300 | Refundable Non-refundable |
Management updates its schedule without a public filing. The date is when management last updated the page, not when a rule changed. Confirm the current schedule with management before you apply.
Considering an apartment here? Send Corey the listing to discuss the building's costs and purchase requirements.
Own an apartment here? Request an apartment-specific pricing review.
Monthly carrying charges in recent sales
- Common charges + taxes, per room
- $371 per room a monthMedian of 5 recorded sales since October 2023Source: recorded sales, refreshed October 2026
- Common charges + taxes, per square foot
- $1.45 per square foot a monthMedian of 4 recorded sales since October 2023Source: recorded sales, refreshed October 2026
Common charges plus real estate taxes, combined into one monthly figure the way New York condominium listings show them. Add a mortgage payment for the monthly outlay. A summary of recorded sales, not a current bill; charges change.
Building staffing and amenities
- Doorman
- Full-time doormanSource: recent listing records
- Elevator
- YesSource: NYC Department of Buildings elevator records
Staffing and amenities as our building profile and recent listing records describe them. A feature not listed is not confirmed absent. Outdoor space, parking and some facilities can belong to particular apartments or to a separate owner; confirm access for the specific apartment.
Local Law 97
- 2024–2029 annual penalty
- $0 (under cap)
- 2030–2034 annual penalty
- $650/yr
- Per unit / month range
- $0 – $4
- Modeled exposure split equally across 15 units (the residential count on the city's lot record). Not an assessed amount; condominium owners are typically charged by each unit's common-interest percentage.
Source: NYC LL84 benchmarking and PLUTO · The Roebling Research Library. City data last refreshed October 2026.
See full Local Law 97 analysis — emissions history, scenarios, methodology →Facade safety — Local Law 11
The latest available FISP filing classified the facade as Safe — no repairs were required at that inspection. A filed Safe grade is not a guarantee of current condition: owners still maintain the facade and, where required, observe parapets each year. Future inspection timing (Local Law 49 of 2025 changed the cycle framework from October 1, 2026), repair and any assessment decisions remain building-specific.
How to read this, and where it comes from
QEWI = Qualified Exterior Wall Inspector — a licensed professional engineer or registered architect who meets DOB’s FISP qualifications and signs the report (the independent expert, not the managing agent).
Source: NYC DOB facade filings (FISP) · The Roebling Research Library. City data last refreshed October 2026.
Recent sales
Compare 910 Union with Park Slope park-block and Grand Army Plaza product using verified apartment areas: 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. Compare the upper-floor A and B lines with second-floor units and 1B using verified interior areas, condition, exposure and dated transactions; the tax-roll area ranges do not establish a price hierarchy. Unit-level transaction history is maintained in The Roebling Research Library and shared with clients during diligence.
Recent closings at this building, from The Roebling Research Library. Prices are the transfer amounts recorded with the NYC Department of Finance; apartment-level detail is checked against the building’s own file in The Roebling Research Library before publishing.
| Date | Unit | Apartment | Price | PPSF | vs. Ask |
|---|---|---|---|---|---|
| Jun 5, 2026 | 4B | 3 BR · 2.5 BA · 1,535 sf | $2,815,000 | $1,834/sf | +8.3% |
| May 11, 2026 | 5B | 3 BR · 2.5 BA · 1,525 sf | $2,825,000 | $1,852/sf | +9.7% |
| Dec 10, 2025 | 1B | 1 BR · 1 BA · 786 sf | $930,000 | $1,183/sf | -2.1% |
| Aug 19, 2025 | 3B | 3 BR · 2.5 BA · 1,535 sf | $2,575,000 | $1,678/sf | -2.8% |
| May 15, 2023 | 4A | 3 BR · 2.5 BA · 1,515 sf | $2,510,000 | $1,657/sf | +0.0% |
| May 16, 2022 | 7A | 3 BR · 1.5 BA · 1,428 sf | $2,400,000 | $1,681/sf | -2.0% |
| Oct 25, 2021 | 1A | 3 BR · 2.5 BA · 1,904 sf | $2,612,500 | $1,372/sf | -6.5% |
| Sep 9, 2021 | 7B | 3 BR · 2 BA · 1,505 sf | $2,300,000 | $1,528/sf | — |
Market read. Most recent trades (2026 to date) cleared a median $1,884/sf (floor-adjusted) across 2 sales. Floor-adjusted means each sale is restated to a constant mix of floors, so the figure can differ from the plain median of the sales listed above. Median listing discount 0.0% from the last ask.
The retrade record
Lines that have traded more than once in the public record — the building’s appreciation arc, apartment by apartment.
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; each condominium apartment is its own tax lot). Apartment-level facts (line, condition, asking-price context) curated and cross-verified in The Roebling Research Library. Not all transactions cross-verify with ACRIS records — sponsor and LLC purchases sometimes record at stipulated values rather than market price; square footage from recorded condo declarations and offering plans.
What would your apartment rent for?
Enter your apartment and I'll send you what it would rent for, from comparable closed leases at Park Union, per listing records and nearby.
At the recent median sale of $2.69M (4 sales in the past 24 months, since November 10, 2024), a buyer putting 25% down would pay about $109,976 to close, or 4.1% of the price.
- Mansion tax: $33,688
- Mortgage recording tax: $38,909
- Title insurance: $12,127
- Attorneys, lender, building fees, reserves and filings: $25,252
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
- 914 President Street — 1899 condominium
- 915 President Street — 1890 co-op
- 916 Eighth Avenue — 1892 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.
Considering a move at Park Union, per listing records?
Request a private building brief with the relevant comparable sales, current and off-market availability, and an apartment-specific view of value.
646.939.7375 · c.cohen@compass.com