* Main shareholders offer 13 euros per share
* Delisting strategy to boost company's business
* Shares down 3.0 percent to 13.06 euros
(Adds detail)
MILAN, Sept 1 (Reuters) - A group of shareholders in Permasteelisa SpA, which owns 61.5 percent of the Italian building cladding company stake, said on Tuesday it had launched an offer for the remaining shares at 13 euros apiece.
The bid for Permasteelisa, whose projects have included the Sydney Opera House and London's Canary Wharf business district, came from companies controlled by Italian Investindustrial LP and Investindustrial IV LP, Alpha investment funds and Andimahia, which represents company executives.
"The promoters of the operation ... propose to insure the necessary shareholder stability in order for Permasteelisa to get future opportunities for development and growth," the shareholders said in a statement.
Permasteelisa shares were down 3.0 percent to 13.06 euros at 1040 GMT.
Investindustrial LP owns 22.3 percent of Permasteelisa and Andimahia has 4.4 percent, the statement said.
Amber Capital LP is part of the agreement on the 61.5 percent stake, it said. Amber Capital has 15.1 percent, according to bourse regulator Consob.
Permasteelisa's products have been used on hundreds of major buildings around the world, including New York's Museum of Modern Art. (Reporting by Nigel Tutt; Editing by Dan Lalor)