- Year built
- 1899
- Type
- Condominium
Own an apartment here? See what it would sell for.
A Private Pricing Opinion — what your apartment at 248 20th 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.
248 20th Street is an 1899 three-family house that is being doubled in height and converted into a four-residence condominium. The Department of Buildings filing describes a vertical and horizontal enlargement from three floors and 32 feet to six floors and 67 feet, with the unit count going from three to four.
The offering totals $8.225 million, or about $2.06 million per residence. The filing allows about 7,825 square feet of construction floor area, roughly 1,960 square feet per home before common areas, so the plan likely prices at roughly $1,100 to $1,300 per square foot, depending on final unit sizes. That would sit below the $1,650 to $1,830 per square foot recorded for the upper homes at 379 12th Street in early 2026.
The Attorney General accepted the plan in July 2026, so the sponsor can sign contracts, but the plan is not yet effective and the building is under construction.
Architecture and residences
Aaron Hockett Architect filed the job in April 2025 as an alteration requiring a new certificate of occupancy that keeps elements of the existing house. The Department of Buildings approved the plans in August 2025 and issued the main permit on December 4, 2025. Separate permits cover excavation support and foundations, structural steel and concrete for the enlargement, a needle beam at the third floor, plumbing, mechanical and sprinkler work. The filing's inspection schedule includes elevator work, which indicates an elevator. A further amendment to the main plans drew objections from the plan examiner in September 2026, which is routine but worth asking about.
Layouts, finishes and outdoor space have not been published. With four homes on six floors, some are likely to be duplexes; Schedule A will set out sizes.
Offering and pricing
Per the offering plan filed with the New York State Attorney General (plan CD250351), the plan was submitted October 30, 2025 and accepted July 7, 2026, with 248 20th Street LLC as sponsor. The record lists four residential units. The total offering price moved from $8,147,000 to $8,225,000, an increase of $78,000, or about 1%; the amendment detail was not available for this review. The plan has not been declared effective, and no units are recorded as sold. No asking prices or listings were found as of October 2026.
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 →What would your apartment rent for?
Enter your apartment and I'll send you what it would rent for, from comparable closed leases at 248 20th Street and nearby.
Buying here? Condo closing costs with a mortgage typically run 3 to 6% 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 plan is not yet effective. A contract signed now becomes binding only when the sponsor declares the plan effective. Your deposit stays in escrow until then. Read the effectiveness terms and the sponsor's right to abandon the plan.
Old house, new building. Ask which parts of the 1899 structure remain and what was replaced. A doubled-height building on old party walls and foundations needs a clear engineering record; the foundation and structural filings are where to start.
Delivery. Ask for the construction schedule and the target date for a temporary certificate of occupancy, and what happens to deposits if delivery slips.
Closing costs. In sponsor sales the buyer customarily pays the New York State transfer tax (0.4%) and the New York City real property transfer tax (1.425% above $500,000), plus the state mansion tax: 1% from $1 million and 1.25% from $2 million. Use the calculators below.
Carrying costs and abatement. The plan's budget will set common charges and projected taxes. No tax abatement has been confirmed in this review.
Comparable buildings
If you're considering 248 20th Street, also look at these South Slope and Park Slope condominiums:
- 179 20th Street — Lumina, an 11-story, 26-residence condominium at Fourth Avenue on the same street
- 205 14th Street — 1915 building converted into five condominiums, sold out in 2024–2025
- 222 16th Street — 32-residence condominium in sales since May 2026
- 379 12th Street — six-residence elevator condominium, sold out between December 2025 and March 2026
- 306 12th Street — four-residence condominium with garden and penthouse duplexes
More Park Slope buildings
- 240 8th Street — 1898 co-op
- 241 13th Street — condominium
- 243 4th Avenue (Parlour), 243 Fourth Avenue — 2018 condominium
- 249 18th Street — 2024 condominium
- 25 Montgomery Place — 1892 condominium
- 25 Plaza Street West — 1941 co-op
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 248 20th 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