“Cost” means the actual cost of rehabilitation, as defined by Chapter 84.26 RCW, which cost shall be at least 25 percent of the assessed valuation of the historic property, exclusive of the assessed value attributable to the land, prior to rehabilitation. The costs shall be incurred within 24 months prior to the date of application and directly resulting from one or more of the following: (A) improvements to an existing building located on or within the perimeters of the original structure; or (B) improvements outside of but directly attached to the original structure which are necessary to make the building fully usable but shall not include rentable/habitable floor space attributable to new construction; or (C) architectural and engineering services attributable to the design of the improvements; or (D) all costs defined as “qualified rehabilitation expenditures” for purposes of the federal historic preservation investment tax credit. (Ord. 2069 § 2 (Exh. B), 2011).