ZURICH, Jan 29 (Reuters) - Holcim's biggest shareholder has given his backing to the building material company's plan to spin off its North American business through a listing on the New York Stock Exchange.

Swiss billionaire Thomas Schmidheiny, the great grandson of Holcim's founder and a former chairman of the company, owns around a 7% stake in the company, according to his spokesperson.

"Mr. Schmidheiny fully supports the separation and listing of the American business, which he believes is in line with industrial logic," the spokesperson told Reuters.

"This creates new growth prospects for both companies in the future," he added. "Holcim has always followed industrial logic, and this transaction makes complete sense in view of the growth opportunities in the United States."

Holcim on Sunday said it will spin off 100% of its North American operations in a New York flotation which could value the business at $30 billion. (Reporting by John Revill; Editing by Jan Harvey)