Illinois Construction Defect Statute
An action based in tort, contract, or otherwise may be commenced within 4 years from the time the plaintiff knew or should have known of the act or omission complained of. No action can be brought after 10 years from the time of such act or omission, but if act or omission is discovered prior to the expiration of 10 years the plaintiff shall have 4 years to bring his action. 735 ILL. COMP. STAT. 5/13-214.