Isaac & Stern Architects is an active New York practice founded in 1988 by Ramy Issac, who trained at the Technion and Pratt; Ralph Kowalczyk became a partner in 2017. The firm signs its own work "Issac | Stern Architects, P.C."; press and municipal records generally use the Isaac spelling. It builds ground-up residential and mixed-use projects across four boroughs, favoring brick, limestone, and precast over glass curtain wall. Ten Manhattan buildings in our catalog carry the credit, all completed from 2016 onward, from six-unit boutique buildings to a 27-story tower on Sixth Avenue.
Who they are
Isaac & Stern Architects is an active New York practice founded in 1988 by Ramy Issac. Issac trained at the Technion in Israel, where he took degrees in architecture and city planning, and holds a master's in architecture from Pratt. He is licensed in New York, New Jersey, Connecticut, and Florida. Ralph Kowalczyk, who trained in Poland and ran his own studio in Europe before joining the office in 2007, became a partner in 2017.
The name is spelled two ways in the record, and both spellings are correct depending on the source. The firm signs its own materials "Issac | Stern Architects, P.C.," after the founder's surname. Architectural and municipal records, and most press, render it "Isaac & Stern Architects." Our building pages carry both. We use the common press spelling on this page and treat the firm's own rendering as the authoritative one for legal documents.
The practice works across Manhattan, Brooklyn, Queens, and the Bronx on ground-up residential buildings, mixed-use projects with retail, condominium conversions, affordable housing, and renovations of older buildings. Ten buildings in our Manhattan catalog carry the credit, and every one of them was completed in 2016 or later.
The work
The Lower East Side and East Village group came first. 50 Clinton Street opened in 2016 for DHA Capital — seven stories, an articulated brick elevation with prominent cornices over a wood-clad ground floor, interiors by Paris Forino. 100 Avenue A followed for Magnum Real Estate Group, eight stories with setbacks above the sixth floor and 32 residences over retail; city records date the filing to 2014, sales launched in 2015, and closings ran through 2016 and 2017. 148 Attorney Street is six stories and six residences, full-floor units above with duplex space below, dated to 2018 in city records and 2019 by the architect. 253 East 7th Street replaced a four-story townhouse demolished at the end of 2015 and completed in 2018; the offering carries seven residences and city records carry eight, which the offering plan settles.
The Midtown and Gramercy work is larger. 249 East 50th Street, from 2019, is 27 residences in limestone panel, massed as an L around an interior garden court with a lower western portion and a taller eastern one. 250 East 21st Street, 2021, runs 13 stories and 54 residences with a limestone facade, French and Juliette windows, and a mansard crown. The Lexi (165 Lexington Avenue), also 2021, is 11 stories in precast masonry drawn from the loft architecture of the surrounding blocks, developed by Brooklyn North Capital with interiors by DNA Design Studios.
Uptown, 427 East 90th Street — Gracie Green — is 11 floors and 21 residences in tan masonry with French casements and glass-enclosed balconies, interiors by GE-T Architects. Its structure was finished around 2019, sales launched in 2022, and first closings came in 2023, a longer gap than the rest of the group.
The two most recent are the largest. 815 Broadway, completed in 2025 and marketed as La Maison Collette, is a brick building near Union Square with a graduated color palette, a tight grid of floor-to-ceiling windows in rectangular, square, and arched openings, balconies from the second floor up, and a landscaped roof. Interiors are by Paris Forino, the developer is Magnum. Unit counts differ across sources: our records carry 23 residences and the published architectural coverage carried 20 at the rendering stage, so read the offering plan. 842 Avenue of the Americas, completing in 2026 for Pro-H Development, is 27 stories with planted terraces and is the tallest building the firm has in our catalog.
Outside Manhattan the office has built Eleven Hancock in Harlem, 71 units with a 22-foot cantilever, 505 Saint Mark's Avenue and 827 Sterling Place in Crown Heights, 450 Grand Avenue in Clinton Hill, and 10 Lenox Avenue.
How the work is regarded
There is no substantial critical writing on this firm. Coverage is trade and architectural press reporting approvals, renderings, and sales launches. No building of theirs holds landmark designation, and none is old enough to be considered for one.
What the buildings show is a consistent set of habits. The firm builds in masonry — brick, limestone panel, precast — rather than in glass curtain wall, on sites where the neighbors are prewar. It uses punched windows in a regular grid, cornices, setbacks, and balconies, and it tends to break larger massings into parts, as at 249 East 50th Street. At 165 Lexington Avenue the precast is explicitly a reference to the loft buildings nearby, and at 250 East 21st Street the mansard is a period gesture on a new building. That posture is what gets projects of this size through community review in low-rise districts, and it is why the buildings read as quiet from across the street.
The finish level buyers actually respond to often comes from a separate interior designer. Paris Forino at 50 Clinton and 815 Broadway, Built In Studio at 100 Avenue A and 148 Attorney, DNA Design Studios at The Lexi, GE-T at Gracie Green. When you compare two of these buildings, you are frequently comparing two interiors consultants working inside a similar envelope.
What the credit means for value
The name carries no premium. It tells you the building is new construction from the last decade, small to mid-size, condominium, and masonry-clad. Price the apartment and the building.
Boutique scale changes the math on common charges. Six to 54 residences means the cost of staff, elevator maintenance, and any capital event divides across a small number of units. One facade repair can move common charges materially in a building of this size. In the largest of the group, the exposure is smaller.
Ask about the staffing model. Buildings at this scale run everything from full-time doormen to virtual doorman systems and part-time superintendents. That decision affects both daily experience and resale, and it is not something you can read off the facade.
New construction pushes the capital cycle out by a decade. These buildings are five to ten years old. Sponsor warranty periods have generally expired, first facade inspection cycles are arriving, and construction defects from the 2015 to 2021 building boom are a live category. Ask for the reserve, the board minutes, and any litigation history against the sponsor. Buildings above 25,000 square feet fall inside Local Law 97; several of the smaller ones here fall below that line, so confirm the square footage before assuming exposure. Our Local Law tools will show a specific building's position.
Unit counts and dates in the public record disagree. 253 East 7th Street carries seven or eight residences depending on the source; 815 Broadway carries 20 or 23; several buildings have a filing date, a completion date, and a first-closing date separated by two or three years. The offering plan is the document that governs.
Check the interiors credit and the finish schedule. In this segment the appliance package, the millwork, and the bath specification are what separate one building from its neighbor, and those decisions belong to the interior designer and the developer.
Buying one today
Comp against new development within a few blocks, not against the neighborhood average. These buildings sell into the recent-construction market. Prewar comps on the same street tell you very little.
Read the offering plan and the amended plans in full. In small buildings the sponsor's remaining units, the commercial unit, and the reserve contribution shape the next five years of board decisions.
Test resale liquidity before you buy. A building with 21 residences produces very few closed sales, so a single distressed print sets the comparable record for the next year. That risk is real and it is priced differently by different lenders.
Look hard at the outdoor space. Balconies, terraces, and setbacks are consistent features of this firm's work and among the most durable value items in the group. They are also the most common source of water infiltration, so read the maintenance record alongside the floor plan.
Working with The Roebling Team
Recent boutique condominiums look interchangeable from the street and behave very differently once you read the financials. The differences that matter — sponsor position, reserve, staffing, defect history — are all in documents rather than in the architecture. If you are buying or selling in one of these buildings, start with a thirty-minute consultation.
Corey Cohen, Principal The Roebling Team at Compass 646.939.7375 · c.cohen@compass.com
Run the numbers
Related architect spotlights
- BKSK Architects — contextual masonry infill in the same districts
- SLCE Architects — the volume practice working the same development pipeline at larger scale
- Robert A.M. Stern Architects — a separate firm, no connection to this one despite the shared name
Isaac & Stern Architects buildings with Roebling building pages
| Building | Completed |
|---|---|
| 100 Avenue A | — |
| 148 Attorney Street | 2018 |
| The Lexi (165 Lexington Avenue) | — |
| 249 East 50th Street | 2019 |
| 250 East 21st Street | 2021 |
| 253 East 7th Street | — |
| 427 East 90th Street | — |
| 50 Clinton Street | 2016 |
| 815 Broadway | 2025 |
| 842 Avenue of the Americas | — |
This page reflects publicly available information and The Roebling Team transaction experience, compiled by The Roebling Research Desk from public records and the offering plans held in The Roebling Research Library. The Roebling Team at Compass does not represent any individual building's management, board, or sponsor. Where sources disagree on attribution or biography, the disagreement is noted rather than resolved. © 2026 The Roebling Team at Compass.