John C. Niedermair, 88, a naval architect who contributed to the design of the famed LST of World War II, died March 6 at Sibley Memorial Hospital. He had cancer.

Mr. Niedermair came to Washington and joined the Navy's Bureau of Ships in 1928. Ten years later he became the bureau's head of its preliminary design branch, a post he held until retiring in 1958. During his years with the bureau, he directed the basic design of about 8,000 ships.

He received the Navy's Distinguished Civilian Service Award for his role in the design of Navy ships, especially the LST (landing ship, tank) that was used in many amphibious landings during World War II, including the Normandy Invasion. He also received the Navy's David Taylor Gold Medal in 1958.

Mr. Niedermair was a native of Union Hill, N.J., and lived in Chevy Chase. He was a 1918 graduate of the Webb Institute of Naval Architecture and Marine Engineering in New York. He served in the Navy during World War I.

His wife, the former Ethel V.M. Irwin, died in 1974. Survivors include five sons, William I., of Seattle, John C., of Glenn Dale, Md., G. Edward, of Tacoma, Wash., Richard M., of Olney, and F. Robert, of Chevy Chase; three daughters, Marion Williams of Lovettsville, Va., Patricia Long of Los Angeles, and Mary Ann Mallinoff of Lanham; a brother, George, and three sisters, Margaret Spencer, Florence Sindlinger, and Anna Undritz, all of Staten Island, N.Y.; 34 grandchildren, and 12 great-grandchildren.