904 Union Street
904 Union Street, Brooklyn, NY 11215
Park Slope, Brooklyn
BBL 3010660023 · BIN 3024699
- Year built
- 1910
- Type
- Cooperative
- Floors
- 4
- Landmark status
- Requires confirmation
- City records and our profile differ. Confirm with building management.
- Dogs and cats
- Permitted
Every recorded sale at this building, 2005–2025
Bedroom-by-bedroom medians, the full transfer record, and how units trade against ask.
- Recent range
- $1.6M – $1.6M
- Listing discount
- 1.6%
- Recorded transfers
- 15
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
The 2005 statements record management fees and a small operating budget; confirm the current managing agent and 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 2005 audited statements record flip-fee income, but the documents on file do not establish the current fee or formula. Sublet terms, financing limits and the board's position on LLC, trust or pied-à-terre purchases are not documented. The materials reviewed do not establish the current rules or whether they are published elsewhere. Get them in writing from the managing agent before pricing.
Pets and in-unit washer/dryer
- Dogs and cats
- PermittedSource: The Roebling Team's building profile
- In-unit washer/dryer
- Not verified
Considering an apartment here? Send Corey the listing to confirm the pet and washer/dryer rules for that apartment.
Own an apartment here? Request an apartment-specific pricing review.
Local Law 97
This building is below the 25,000 sq ft threshold at which LL97 limits apply to a building on its own. It is still covered if it shares a tax lot or condominium board with buildings totaling over 50,000 sq ft; confirm on DOB’s covered-buildings list.
See full Local Law 97 analysis →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 separate buyers throughout the 2000s, 2010s and 2025, so the building has a documented resale market. Count qualifying arm’s-length transfers over a defined period to establish resale frequency, and compare individual layouts before interpreting a building average.
Unit-level transaction history is maintained in The Roebling Research Library and shared with clients during diligence.
Recent transfers 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 | vs. Ask |
|---|---|---|---|---|
| Oct 9, 2025 | 3A | 1 BA | $415,000 | +4.0% |
| Jun 25, 2025 | 1C | 2 BR · 2.5 BA | $1,550,000 | -1.6% |
| Mar 19, 2015 | 2A | $290,000 | -3.0% | |
| Jun 26, 2014 | 1C | 2 BR | $999,900 | +11.2% |
| May 9, 2013 | 3C | 2 BR | $450,000 | -18.0% |
| Apr 28, 2009 | 3C | 2 BR | $450,000 | -8.0% |
| Nov 21, 2006 | 4A | 2 BR | $425,000 | +0.0% |
Market read. Median listing discount 1.6% from the last ask — a recurring negotiation gap worth pricing into any offer or listing strategy.
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 3-01066-0023). 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.
What would your apartment rent for?
Enter your apartment and I'll send you what it would rent for, from comparable closed leases at 904 Union Street and nearby.
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 2005 statements record transfer-fee income; confirm the current formula, payer and exceptions, alongside the underlying mortgage and any assessment. These documents support net-proceeds planning and lender review without guaranteeing timing.
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
- 862 Carroll Street — 1889 condominium
- 9 Prospect Park West — 1928 co-op
- 90 Eighth Avenue — 1927 co-op by Sugarman & Berger
- 910 Union Street (Park Union) — 1931 condominium
- 914 President Street — 1899 condominium
- 915 President Street — 1890 co-op
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.
646.939.7375 · c.cohen@compass.com