Robert F. Gatje, FAIA, known for his extensive collaboration with AIA Gold Medalist Marcel Breuer, died April 1, 2018 in New York City after suffering a stroke. He was 90.

Gatje was born on November 27, 1927 in Brooklyn, N.Y., to Frederick C. Gatje and Erna Kelting. He attended Brooklyn Technical High School and Deep Springs College before spending time in the United States Army Corps of Engineers between 1946 and 1947. In 1951, he graduated from Cornell University with a B.Arch. That same year, he became a Fulbright Scholar at London’s Architectural Association School.

In 1953, Gatje joined Breuer’s office as a draftsman and stayed until 1982. As he recalled in his book Marcel Breuer: A Memoir, it was “one of the best places for a young architect to work in New York City.” As an associate and partner, Gatje took part in the design for projects at the Institute for Advanced Study in Princeton, New Jersey (1957) and New York University in the Bronx (1961), as well as IBM La Gaude, a distinctive concrete, double Y-shaped building in France (1962).

Gatje later became the resident director of Breuer’s European office, overseeing the design of a residential quarter in Bayonne, France (1966) and the Flaine ski resort (1969), which was subsequently listed in the French Historical Monuments Survey. While acknowledging that his mentor’s method of design was “rather mysterious,” Gatje also pointed out in a 2015 interview that Breuer was not a Brutalist architect, although much of Breuer’s architecture was poured-in-place concrete. “For one thing, the term was not used at the time—certainly not by us in the office, “ he said. The label was a misinterpretation of the French phrase béton brut, or “rough-formed concrete,” and did not accurately fit the buildings that were described as such, Gatje explained.

Among his former colleagues, Gatje was well respected. “He was the ideal foil for Marcel Breuer,” recalls Peter Samton, FAIA, who worked for Gatje from 1960 to late 1962. “Breuer was fast and not easy to understand; Bob was ever patient and mindful of the difficulty in understanding Breuer.”

From 1975 to 1976, Gatje served as the president of the American Institute of Architects’ New York chapter.

Six years following Breuer’s retirement in 1976, Gatje formed an office with Tician Papachristou and Hamilton Smith, both of whom had also been on Breuer’s staff. During the firm’s four-year existence, Gatje was partner-in-charge of projects for IBM, United Airlines, and the Broward County Main Library in Florida.

In 1987, Gatje joined the firm headed by Richard Meier, whom he had met in his early days at Breuer’s office. He left in 1995 to become an author, arbitrator, and architect on his own. His most recent book, Great Public Squares: An Architect’s Selection, explores plazas in both Europe and the U.S.

Gatje is survived by his daughters Alexandra Gatje, Marianna Perrier, and Margot Small; his sister Norma Smith; and his longtime partner Susan Witter.