An action based on breach of warranty or deficiency in the design, planning, or construction of improvement must be brought within 4 years of alleged act or omission contributing to such breach of warranty or deficiency. If such cause of action is not, and could not be, discovered within 4 years (or within 1 year before the end of the 4 year period), then the action may be commenced within 2 years of discovery or from the date of discovery of facts which should reasonably lead to discovery, but in any event no more than 10 years from the act giving rise to the action. NEB. REV. STAT. ยง 25-223.