904 Union Street
904 Union Street, Brooklyn, NY 11215
BBL 3010660023 · BIN 3024699
- Year built
- 1910
- Type
- Cooperative
- Units
- 12
- Floors
- 4
- Landmark
- No
Own an apartment here? See what it would sell for.
A Private Pricing Opinion — what your apartment at 904 Union Street 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.
904 Union Street is one of the smallest cooperatives within a block of Grand Army Plaza. It has about a dozen apartments in a 1910 walk-up, and no staff or amenities to speak of. It is a building for someone who wants the Prospect Park end of Park Slope in a four-story house rather than an elevator building on the Plaza.
The block is easy to mix up. Within about 100 feet on Union Street sit three ownership structures: this cooperative (lot 23, share transfers), the seven-story 910 Union Street condominium, and the 1 Prospect Park West condominium on the corner. The lot number settles which one a record refers to.
It also sits just outside the 1973 Park Slope Historic District, which takes in 902 Union Street next door. Exterior work here does not need Landmarks approval, as it would one door west.
Architecture and unit composition
The engineering report in the offering plan describes a four-story brick and masonry building with wood joists, a full cellar, a skylit stair and no elevator. The building sits on a 2,250-square-foot lot. At the 1982 conversion it held 15 small apartments. Most were two-space layouts, with a kitchen-dining area and a living area divided by a low partition, and each had its own bath.
Combinations have reshaped that stock. ACRIS records a third- and fourth-floor pair conveyed as one unit, and the count has fallen from 15 to 13 (2005) to 12 (city records today). Ask for the current floor plan and share allocation; don't assume the plan-era layout.
Building operations
This is a small cooperative with a managing agent (the 2005 statements carry management fees) and a small budget. In 2005, maintenance brought in about $86,000 a year, and real estate taxes and fuel oil were the largest expenses. The audited statements recorded laundry income that year, although the offering plan said there was no laundry room at conversion. Confirm what laundry is there now.
Capital posture is the diligence item. In 2003 the corporation refinanced into a $225,000 self-amortizing first mortgage, scheduled to be fully repaid in March 2023. ACRIS then records a 2015 mortgage consolidation and modification. The current balance, rate and maturity must come from the current financial statements. The 2005 statements also showed special-assessment income and noted that no reserve study had been done.
DOB records show a 2016 application for façade restoration and roof replacement, which was disapproved at plan examination, and a sidewalk-shed permit in 2017. Ask the managing agent for the current Local Law 11 façade cycle status and whether that work has been completed.
Policy framework
The house rules on file are short and conventional, and the board can amend them by resolution, so get the current version. The corporation charges a flip fee, which shows in its books as income, but the documents on file do not state the formula. Sublet terms, financing limits and the board's position on LLC, trust or pied-à-terre purchases are not documented. With about a dozen shareholders, each of these is a board decision and not a posted policy. Get them in writing from the managing agent before pricing.
Recent sales
904 Union Street trades as small prewar walk-up co-op stock at the Prospect Park end of Park Slope. It is priced per room, with renovation, light and floor level driving the spread. Top-floor apartments cost buyers a walk-up premium to reach, and combined apartments trade in a different price band from the original small layouts. ACRIS shows share transfers to unrelated buyers throughout the 2000s, 2010s and 2025, so the building has a documented resale market. With so few apartments, though, only a handful trade in any year, so any single sale moves the building's apparent price level.
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 transfers 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 |
|---|---|---|
| Jul 10, 2025 | 1C | $1,550,000 |
| Aug 7, 2017 | 13 | $749,000 |
| Dec 24, 2014 | 1B | $565,000 |
| Jul 11, 2014 | 1C | $999,900 |
| Sep 7, 2010 | 1C | $705,000 |
| Oct 18, 2005 | 1C 2C | $739,000 |
Sales sourced from NYC Department of Finance recorded transfers (BBL 3-01066-0023) 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.
Buying here? Co-op closing costs typically run 2 to 3% of the price. See NYC co-op and condo closing costs, line by line.
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What to know if you’re buying
Underwrite the building, not just the apartment. In a building this size, one roof or façade job can mean an assessment. Ask for the last three years of financial statements, the current mortgage terms, and any planned capital work.
Confirm the apartment's history. Combinations and reconfigurations are common here. Make sure the alteration agreement, share allocation and proprietary lease match the apartment you're buying.
Expect a full board package. No written board requirements are on file. Assume a full package and an interview, and confirm the financing limit and minimum down payment before you bid.
What to know if you’re selling
Get the flip fee formula and current financials early. The corporation collects a transfer fee, and buyers' lenders will ask about the underlying mortgage and any assessment. Having both ready protects your net and shortens underwriting.
Comparable buildings
If you're considering 904 Union Street, also evaluate:
- 1 Prospect Park West, the condominium at the corner of the same block; the fee-simple, amenitized alternative at the same address cluster
- 86 Prospect Park West, a cooperative of two four-story walk-ups offered in 1978; the closest match in format near the park
- 10 Montgomery Place, a cooperative of two four-story walk-ups in the historic district
- 375 Lincoln Place, a 1921 four-story co-op; a larger walk-up alternative
- 75 Prospect Park West, a 24-apartment prewar co-op on the park; the elevator step-up at similar scale
- 90 8th Avenue, a prewar elevator co-op one block west on Eighth Avenue
More Park Slope buildings
- 86 Prospect Park West — 1908 co-op
- 9 Prospect Park West — 1928 co-op
- 90 Eighth Avenue — 1927 co-op by Sugarman & Berger
- 910 Union Street (Park Union) — 1931 condominium
- Baltic Park Slope (613 Baltic Street) — 2016 condominium
- The Park Pavilion, 372 15th Street — 2005 condominium
The neighborhood
For the full neighborhood — its buildings, character, and market — read The Roebling Team Guide to Park Slope.
The full playbook — what goes in the package, how boards read your financials, the interview, and the timeline — plus sample cover, reference, and personal letters you can adapt.
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 904 Union Street?
Request a private building brief with the relevant comparable sales, current and off-market availability, and an apartment-specific view of value.