Dr. Ferdinand Zach, 81, an authority on the restoration of rare books who retired in 1965 as head of the bindery of Catholic University's Mullen Library, died in a hospital in Tortola, British Virgin Islands, after a heart attack. He was on vacation.

He came to Washington in 1943 to help establish the expanded bindery and restoration facility at Catholic University. In addition to his restoration work, he was recognized for his creation of binding designs and for tutoring apprentices.

Dr. Zach had supervised the restoration of books for the Kennedy White House, the Interior Department's Division of Museums, and the National Geographic Society.

His last major restoration was a copy of Gower's "Confessior Amantis" for the University of North Carolina at Chapel Hill. The book had been printed by William Caxton in 1483.

Dr. Zach was born in Teplitz, Bohemia, and earned a doctoral degree in civil and canon law at the University of Prague.

He served as an officer in the Austrian Army during World War I. He was a Czechoslovak trade commissioner in Africa and managed a theater in Algeciras, Spain, before coming to this country in 1937.

Dr. Zach lectured in history at the University of California in Berkeley, where he also worked as an art appraiser. He was a chef in a Santa Barbara restaurant before coming to Washington.

He had undergone a laryngectomy in 1954 for treatment of cancer of the throat, and was a member of the Lost Chord Club, the Washington chapter of the International Association of Laryngectomies.

Survivors include his wife, Elizabeth Baker Zach, a daughter, Sarah Elizabeth, and a son, Robert Ferdinand, all of the home in Washington. CAPTION: Picture, FERDINAND ZACH