R. Byng Duvall, 57, retired owner of a general contracting firm in Kensington, where he had been a civic leader, died of cancer Tuesday at the Veterans Administration Hospital in Washington.

He was head of the Duvall Engineering Co., from its establishment in 1958 until he retired in January 1978. The firm built the Kensington Park Library and was associated with apartment and other commercial buildings.

Mr. Duvall had been a founding director and was the first president of the Chevy Chase Bank and Trust Co. from 1969 to 1974.

A former president of the Kensington-Wheaton Junior Chamber of Commerce, he had served as vice mayor and a member of the Town Council of Kensington.

In 1960, he ran unsuccessfully in the Republican primary as a candidate for Congress from Maryland's 6th District.

Born in Washington, Mr. Duvall was a lifelong resident of this area. He earned a degree in accounting and business administration from Benjamin Franklin University and did graduate work at George Washington University.

During World War II, he served in the Pacific as a bomber pilot with the U.S. Army Air Corps. After the war, he worked as an auditor with Pepco until starting his own business.

He was a member of the Air Craft Owners and Pilots Association and the Congressional Country Club.

He is survived by his wife, Elizabeth, and a son, Martin Byng, of the home in Kensington; a daughter, Julie Stull, of Gaithersburg, and a sister, Katherine Montee, of Cherry Hill, N.J.

The family suggests that expressions of sympathy be in the form of contributions to Holy Redeemer Catholic Church in Kensington.