qualified improvement property
(6) Qualified improvement property (A) In general The term “qualified improvement property” means any improvement made by the taxpayer to an interior portion of a building which is nonresidential real property if such improvement is placed in service after the date such building was first placed in service. (B) Certain improvements not included Such term shall not include any improvement for which the expenditure is attributable to— (i) the enlargement of the building, (ii) any elevator or escalator, or (iii) the internal structural framework of the building.