- Year built
- 1940
- Type
- Cooperative
- Amenities
- Private garden and terrace associated with the lower home; in-home laundry
- Landmark status
- Not an individual landmark; not in a historic district
- NYC Landmarks Preservation Commission and City Planning records, updated February 2026
Own an apartment here? See what it would sell for.
A Private Pricing Opinion — what your apartment at 309 Sixth Avenue 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.
About the building
309 Sixth Avenue is a four-story cooperative with four residences in central Park Slope. The building's small inventory includes broad three-bedroom homes and a lower residence with private outdoor space. City records date the property to 1940. Its recorded floor area exceeds a simple comparison with the current R6B allowance, which does not by itself establish legal zoning floor area or what future work is permitted.
The apartments use floor-through layouts with front and rear rooms. The lower home connects to a private garden and terrace, while an upper-floor three-bedroom plan measures approximately 1,350 square feet. Fireplaces and retained interior details appear alongside modern renovations; laundry is accommodated within the homes. Access to the upper floors is by stairs, and the garden is reserved for a particular residence.
Building staffing and amenities
- Elevator
- NoSource: NYC Department of City Planning records (PLUTO)
- Amenities noted
- GardenSource: The Roebling Team's building profile
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
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
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 |
|---|---|---|---|---|
| Jun 26, 2026 | 1 | 3 BR · 2.5 BA | $2,635,000 | +14.6% |
| Jul 17, 2013 | 4 | 3 BR | $1,455,000 | -2.9% |
| Mar 9, 2011 | 1 | 3 BR | $998,000 | -5.0% |
The retrade record
Lines that have traded more than once in the public record — the building’s appreciation arc, apartment by apartment.
Sales sourced from NYC Department of Finance recorded transfers (BBL 3-00976-0007). 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.
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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
The garden and upper-floor homes carry different maintenance questions. The lower residence's garden drainage and terrace connection affect both its private space and the building envelope. The proprietary lease should establish which work belongs to that shareholder and which is shared by the four-home cooperative. Major common repairs are funded by a very small ownership group.
Comparable buildings
- 240 Eighth Street: A larger former-factory cooperative with elevator service and a courtyard.
- 904 Union Street: A prewar cooperative with a similarly modest building height.
- Sterling Atrium: A small cooperative with a different low-rise residential configuration.
More Park Slope buildings
- 306 Twelfth Street — condominium
- 308 14th Street — 2024 condominium
- 309 2nd Street (The Heritage at Park Slope) — 2008 condominium by Karl Fischer Architects
- 31 Eighth Avenue — 1888 co-op
- 313 Sixth Avenue — 1935 co-op
- 316 22nd Street — 2023 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.
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