property 30 years (iv) Nonresidential real property 40 years (v) Any railroad grading or tunnel bore or water utility property 50 years . (5) Conforming amendments (A) Clause (i) of section 168(k)(2)(A) is amended— (i) in subclause (II), by inserting or after the comma, (ii) in subclause (III), by striking or at the end, and (iii) by striking subclause (IV). (B) Section 168 is amended— (i) in subsection (e), as amended by paragraph (2)(B), by adding at the end the following: (6) Qualified improvement property (A) In general The term qualified improvement property means any improvement 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. . (ii) in subsection (k), by striking paragraph (3). (c) Effective date (1) Application The amendments made by this section shall apply to property placed in service after December 31, 2017. (2) Shorter recovery period or more accelerated depreciation method In the case of property placed in service before January 1, 2018, if the amendments made by this section result in— (A) an applicable recovery period which is less than the applicable recovery period for such property before enactment of such amendments, or (B) an applicable depreciation method which is more accelerated than the applicable depreciation method for such property before enactment of such amendments, the depreciation deduction for such property shall, for any taxable year beginning after December 31, 2017, be determined as if such property were placed in service on January 1, 2018. 13205. Use of alternative depreciation system for electing farming businesses (a) In general Section 168(g)(1), as amended by section 13204, is amended by striking