If your roommate's name is on the lease with yours, you cannot evict her. But if not, she is subletting from you, and you must use standard Washington procedures to evict her, including a notice to vacate, followed by a suit for unlawful detainer.
Eviction Laws in Washington State
In Washington, only a landlord can evict a tenant. If both you and your roommate are on the lease or rental agreement, you are co-tenants and cannot evict each other. And if your landlord ends your tenancy, both of you lose the right to occupy the unit.
If only your name is on the lease, your roommate is subletting from you. In that case, you are the landlord and you have authority to evict her, but be sure to follow state laws and procedures carefully.
Procedure to Terminate a Tenancy in Washington
An eviction in Washington begins with a notice terminating the tenancy. Prepare the notice and give it to your roommate personally to start the process. Notice requirements are different depending on the reason for the eviction. If you are evicting your roommate because he didn't pay rent, you must give a three-day notice. If you are evicting for violations of the rental agreement, you give a 10-day notice.
If your roommate has a lease agreement with you for a set term, you cannot end the tenancy early without a valid reason, such as violation of rental agreement terms or failure to pay rent. If not, your roommate is considered to be on a month-to-month tenancy. You can terminate a month-to-month tenancy without cause in Washington by giving 20-days notice. Note that some of the rules and procedures used in Seattle vary from those used in the rest of the state.
Filing a Complaint for Unlawful Detainer
If the period of time set out in the notice expires, and your roommate hasn't moved out voluntarily, file a summons and complaint for unlawful detainer. The clerk will stamp the complaint with the date by which a response must be filed. If you are uncertain about how to fill out the form, consult with an attorney. It is important that you proceed according to law.
Arrange to have a third-party personally hand your roommate a copy of the papers. Your roommate can challenge the eviction by responding to the complaint in the time frame provided. If the complaint is not challenged, the court will likely grant the eviction order.
If your roommate responds and challenges the eviction or raises defenses, the court will schedule a hearing on the matter. Take all of your evidence and witnesses to the hearing. The judge will give both you and your roommate an opportunity to present your cases before making a final decision about whether to grant an order for eviction.