4W21
4 West 21st Street, New York, NY 10010
Flatiron
BBL 1008220045 · BIN 1087636
- Year built
- 2005
- Type
- Condop
- Landmark
- No
Every recorded sale at this building, 2006–2026
Price-per-square-foot over time, the line- and floor-premium curves, and every recorded sale.
- Median $/sf
- $1,318
- Listing discount
- 4.1%
- Recorded sales
- 169
- On record
- 2006–2026
Own an apartment here? See what it would sell for.
A Private Pricing Opinion — what your apartment at 4W21 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.
4W21 is the rare new-millennium building in the Flatiron that managed to feel of its neighborhood rather than imposed on it. Designed by Hugh Hardy of H3 Hardy Collaboration Architecture for The Brodsky Organization and completed in the mid-2000s, it takes the area's defining grammar — the stone-and-cast-iron loft — and re-renders it in a shimmering, articulated facade of glass and stainless steel. The result is a contemporary building that reads as a respectful descendant of the Flatiron's industrial architecture rather than a generic curtain wall.
Just off Fifth Avenue, the building sits at the practical center of downtown: Union Square, Gramercy, Chelsea, and Midtown all within easy reach. It was conceived as a full-service building for buyers who wanted modern construction, real amenities including an on-site garage, and the lofty proportions the neighborhood is known for — with floor-to-ceiling windows and ceilings approaching ten feet.
Structurally, 4W21 is a cooperative operated as a "condop" — a co-op that functions with much of the flexibility of a condominium. That hybrid is the building's quiet advantage: the maintenance-and-management simplicity of co-op ownership paired with notably looser rules than a traditional pre-war co-op board.
Architecture and unit composition
Hardy's facade is the building's signature — an articulated skin of glass and stainless steel that catches light and echoes the rhythm of the loft buildings around it, modern but grounded in context. Behind it, the homes deliver the proportions buyers come to the Flatiron for: floor-to-ceiling windows, hardwood floors, and ceiling heights near ten feet.
The 54 residences run from one-bedrooms through three-bedroom homes, with a handful of terraced two-bedrooms and two penthouses crowning the building. Kitchens were finished to a high contemporary specification — high-gloss Italian cabinetry, premium appliances, and stone counters — and the open layouts read as updated lofts. The mix favors two-bedroom homes, with the larger and terraced units and the penthouses commanding the building's strongest pricing.
Building operations
4W21 operates as a full-service condop with a full-time doorman and resident staff. For a building of its size, the amenity package is genuinely useful: an on-site parking garage — a real rarity in the Flatiron — plus a fitness room, a roof deck, bicycle storage, and private storage.
The condop structure is the operational headline. Because the building is a cooperative that functions with condominium-like flexibility, buyers generally find a lighter approval process and more accommodating rules than at a conventional co-op, while still benefiting from the single, all-in monthly maintenance and the cohesive management a co-op provides. Specific board policies on financing, subletting, pieds-à-terre, and pets follow the building's proprietary lease and house rules; the structure is designed to be more permissive than the pre-war co-op stock nearby. The location — steps from Fifth Avenue with Union Square, Gramercy, Chelsea, and Midtown transit and retail all close — does the rest.
Local Law 97
- 2024–2029 annual penalty
- $0 (under cap)
- 2030–2034 annual penalty
- $40,298/yr
- Per unit / month range
- $0 – $62
Source: NYC LL84 benchmarking and PLUTO · The Roebling Research Library. City record last verified September 2026.
See full Local Law 97 analysis — emissions history, scenarios, methodology →Facade safety — Local Law 11
The latest available filing classified the facade as SWARMP — Safe With A Repair and Maintenance Program: the engineer identified conditions requiring monitoring or repair before the next inspection cycle. The scope, timeline, and how the building funds the work are building-specific — we review the filings and board materials for you.
How to read this, and where it comes from
QEWI = Qualified Exterior Wall Inspector — the licensed engineer the city requires to sign the report (the independent expert, not the managing agent).
Penalties shown are amounts DOB assessed against filings on record across 2010–15 to 2020–25. The FISP dataset does not record whether they were paid, contested or remain open, so treat the figure as history rather than a current balance and confirm the building’s standing with the managing agent.
Source: NYC DOB facade filings (FISP) · The Roebling Research Library. City record last verified September 2026.
Recent sales
Recent transfers at this building, curated by The Roebling Team research desk. 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 |
|---|---|---|---|---|---|
| Mar 18, 2026 | 16A | 2 BR · 2 BA · 1,444 sf | $1,550,000 | $1,073/sf | +0.0% |
| Oct 30, 2025 | 10D | 2 BR · 2.5 BA · 1,518 sf | $1,185,000 | $781/sf | -12.2% |
| Sep 17, 2025 | 2D | 2 BR · 2.5 BA · 1,620 sf | $1,435,000 | $886/sf | -2.7% |
| May 5, 2025 | 14D | 2 BR · 2.5 BA · 1,518 sf | $1,350,000 | $889/sf | -1.8% |
| Jul 15, 2024 | 4D | 2 BR · 2.5 BA · 1,495 sf | $1,300,000 | $870/sf | -6.8% |
| Jun 28, 2024 | 11B | 3 BR · 3 BA · 1,674 sf | $1,450,000 | $866/sf | -6.5% |
| Jun 27, 2024 | 4B | 2 BR · 3 BA · 1,500 sf | $1,169,561 | $780/sf | -8.2% |
| May 30, 2024 | 7C | 2 BR · 2 BA · 1,256 sf | $1,295,000 | $1,031/sf | +0.0% |
Market read. Most recent trades (2026) cleared a median $1,318/sf across 1 sale. Median listing discount 4.1% 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 1-00822-0045) 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; square footage on co-ops is not officially recorded, figures shown are approximate.
What to know if you’re buying
The first thing to understand is the structure: this is a cooperative operated as a condop, which typically means a lighter approval path and more flexible rules than a traditional co-op while retaining co-op simplicity. Confirm the building's current posture on financing, subletting, and pieds-à-terre as part of your offer, since those are the levers that distinguish a condop from a standard co-op. Beyond structure, focus diligence on floor and exposure, the layout and whether the home has a terrace, and the scope of any renovation. The on-site garage is a genuine differentiator in this neighborhood and worth weighing. Review the building's financials and the all-in maintenance, and lean into the location — few Flatiron addresses are this central.
What to know if you’re selling
Lead with the building's distinct combination: a Hugh Hardy-designed glass-and-steel facade, loft-scale homes with near-ten-foot ceilings, a rare on-site garage and roof deck, and the flexibility of condop ownership — a package the surrounding pre-war co-ops and conventional lofts cannot match. Benchmark to comparable Flatiron buildings and emphasize the structure's looser rules to buyers who want condo-like flexibility without condo pricing. Stage to the home's light, ceiling height, and any terrace, and if the sale includes garage access or a deeded space, make it prominent — it is a meaningful draw in this corridor.
Comparable buildings
If you're considering 4W21, also evaluate these Flatiron and nearby downtown peers:
- 15 West 20th Street — Flatiron luxury building a block south
- 16 West 19th Street — boutique Flatiron building nearby
- 16 West 16th Street — established building to the south
- 100 West 15th Street — full-service Flatiron / Chelsea building
- 101 West 24th Street — modern Chelsea / Flatiron tower
The neighborhood
For the full corridor — architecture, schools, transit, and pricing across Flatiron — read The Roebling Team Guide to Flatiron.
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 4W21?
Request a private building brief with the relevant comparable sales, current and off-market availability, and an apartment-specific view of value.