Carl W. Ernst Jr., 62, an associate of the Washington architectural and engineering firm of John S. Samperton and Associates, died of cancer Monday at Mount Vernon Hospital in Alexandria.

Mr. Ernst joined the architectural firm of Chatelain, Gauger and Nolan, which later became John S. Samperton and Associates, in 1960, and later became a partner. He became an associate of Samperton and Associates when the firm was established in 1979.

Before joining Chatelain, Gauger and Nolan, Mr. Ernst worked for architectural firms in Baltimore, Pennsylvania and Alexandria.

A native of Lancaster, Pa., he earned a bachelor's degree from Pennsylvania State University, and then attended Princeton University for two years on a scholarship. He was awarded the Princeton Prize.

In the late 1940s, Mr. Ernst served on the faculty of the Carnegie Institute of Technology, now Carnegie-Mellon University, in Pittsburgh.

A Washington-area resident since 1950, he lived in Alexandria and was a member and former vestryman of St. Luke's Episcopal church there.

Mr. Ernst was a member of the American Institute of Architects, the Metropolitan Washington Board of Trade, the Washington Building Congress, the Cosmopolitan Club and Belle Haven Country Club in Alexandria.

Survivors include his wife, the former Mary Ellen Weaver, of Alexandria; two daughters, Carol Hastings of Seattle, and Barbara Noall of Denver; a sister, Kathleen Herr of Lancaster, Pa., and five grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to St. Luke's Episcopal Church Memorial Fund in Alexandria.