Paul H. Otto, 68, chairman of the board and retired president of Washington Stair and Ornamental Iron Works Inc., died of cardiac arrest Friday at Suburban Hospital in Bethesda.

Born and reared in Washington, Mr. Otto graduated from McKinley Technical High School and earned a bachelor's degree from Catholic University's School of Engineering and Architecture.

He then joined his late father, Louis H., in the family business, the Washington Stair and Ornamental Iron Works, and became it's first president when the firm was incorporated in 1954. He retired as president in 1975 and served as board chairman until his death.

Mr. Otto served on the advisory board of the branch banks division of American Security and Trust. He was a past president of the Northeast Kiwanis Club, a former member of the Business Round Table, an association of executives, and past secretary of the Loyal Order of Jesters. aHe was a 33rd degree Mason and a member of the Almas Temple and a former deacon of the Chevy Chase Presbyterial Church. He was a member of the Columbia Country Club in Chevy Chase.

Survivors include his wife, Winifred J.; a son, Paul L., of Bethesda; a daughter, Suson O. Getz of Bentonville, Va.; a sister, Margaret Billings of Tiburon, Calif., and one grandson.

The family suggests that expressions of sympathy be in the form of contributions to the American Heart Association or to a favorite charity.