Va. Code § 55.1-2823
When any fence (i) that has been built and used by adjoining landowners as a division fence, or any fence that has been built by one landowner and the other landowner is afterwards required to pay half of the value or expense of such fence under the provisions contained in this article, and (ii) that has thereby become a division fence between such lands, becomes out of repair to the extent that it is no longer a lawful fence, either one of such adjoining landowners may give written notice to the other, or to his agent, of his desire and intention to repair such fence and require him to repair his half of such fence. If the landowner receiving written notice fails to repair his half within 30 days after being so notified, the one giving such notice may then repair the entire fence so as to make it a lawful fence, and the other shall be liable to him for one-half of the expense of such repairs.
Va. Code § 55.1-2823