N.D. Cent. Code § 57-02.2-02: Improvement defined

In this chapter, unless the context or subject matter otherwise requires, the term "improvement" means the renovation, remodeling, or alteration, but not the replacement, of an existing building or structure for use for commercial or residential purposes. An improvement for residential purposes is limited to a building or structure at least twenty-five years old. An addition constructed to an existing building or structure to enlarge it is an improvement for the purposes of this chapter.