Wash. Rev. Code § 36.70C.050
If the applicant for the land use approval is not the owner of the real property at issue, and if the owner is not accurately identified in the records referred to in RCW 36.70C.040(2) (b) and (c), the applicant shall be responsible for promptly securing the joinder of the owners. In addition, within fourteen days after service each party initially named by the petitioner shall disclose to the other parties the name and address of any person whom such party knows may be needed for just adjudication of the petition, and the petitioner shall promptly name and serve any such person whom the petitioner agrees may be needed for just adjudication. If such a person is named and served before the initial hearing, leave of court for the joinder is not required, and the petitioner shall provide the newly joined party with copies of the pleadings filed before the party's joinder. Failure by the petitioner to name or serve, within the time required by RCW 36.70C.040(3), persons who are needed for just adjudication but who are not identified in the records referred to in RCW 36.70C.040(2)(b), or in RCW 36.70C.040(2)(c) if applicable, shall not deprive the court of jurisdiction to hear the land use petition.
RCW 36.70C.050