John J. Durkin, 79, a civilian engineer with the Army's Research and Development Laboratory here for 20 years before retiring in 1970, died of congestive heart failure Tuesday at Mount Vernon Hospital in Alexandria.

Mr. Durkin, who lived in Alexandria, was a native of Cleveland, where he earned a bachelor's degree in civil engineering at the Case Institute of Technology. He moved to the Washington area in 1940 and began working as an engineer for the Army later that year.

He was a member of the parish of the St. Louis Catholic Church in Alexandria. He was a charter member and past president of the Serra Club, a religious organization, at Fort Belvoir.

Mr. Durkin also was a member of the Holy Name Society and the Nocturnal Adoration Society and was a 4th Degree member of the Knights of Columbus. He was a member of the board of regents of the Ascension Academy in Alexandria.

Survivors include his wife, the former Laurie Murray, of Alexandria; four sons, John M. of Vienna, Lawrence E. of Wilmington, Del., Thomas H. of Evansville, Ind., and James V. of Derwood, Md.; a daughter, Mary Jo Ibanez of Silver Spring; two sisters, Helen C. and Elizabeth F. Durkin, both of Arlington, and 10 grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the Vocational Fund of the Catholic Diocese of Arlington, or the Cystic Fibrosis Clinic, Deaconess Hospital, 600 Mary St., Evansville, Ind., 47747.