Understand Liens.
Anyone hired by your contractor to work on your property, or to provide materials for your project, who has not been paid, has the right to force you, the consumer, to pay them by making a claim against your property.
This claim is known as a "lien" specifically, a "construction lien." A lien is filed within 90 days of work stoppage or delivery of materials. Washington state law allows this — and it is an easy way to get yourself in financial trouble. Fortunately, there are ways to protect yourself.