Va. Code § 33.2-1007
In acquiring rights-of-way for highway construction, reconstruction, or improvement, and lands incidental to such construction, reconstruction, or improvement, the Commissioner of Highways is authorized and empowered, whenever a portion of a tract of land is to be utilized for right-of-way or a purpose incidental to the construction, reconstruction, or improvement of a public highway, to acquire by purchase, gift, or the exercise of the power of eminent domain the entire tract of land or any part thereof whenever (i) the remainder of such tract or part thereof can no longer be utilized for the purpose for which the entire tract is then being utilized; (ii) a portion of a building is to be taken; (iii) the cost of removal or relocation of the buildings or other improvements on the remaining portion necessitated by the taking would exceed the cost of destroying such buildings or other improvements; (iv) the highway project will leave the remaining portions without a means of access to a public highway; or (v) in the judgment of the Commissioner of Highways the resulting damages to the remainder of such tract or part thereof lying outside the proposed right-of-way, or the area being acquired for a purpose incidental to the construction, reconstruction, or improvement of a public highway, will approximate or equal the fair market value of such remaining lands. However, the Commissioner of Highways shall not acquire the remainder of such tracts by purchase where the remaining portion is in excess of 10 acres or by condemnation where the remaining portion is in excess of two acres. Nothing contained in this section shall be construed as preventing the Commissioner of Highways from complying, where applicable, with the provisions of § 25.1-417.
Va. Code § 33.2-1007