I had a contract with landscaper which was paid in full . my contractor had him build a wall and now he request payment from me

From the information you've provided above, especially if you required your landscaper to get your signature on any changes to the contract, it would appear that your landscaper is liable. It would be best to try to work something out with him and put this behind you. If you can't work something out, there are quite a number of legal requirements that your landscaper and subcontractor must have complied with completely before they can file a valid and enforceable lien. To file a valid lien, the subcontractor is required to give you "preclaim notice of lien" within 90 days of completing the work. This is because he wasn't working directly with you, and you were entitled to proper notice that someone other than the landscaper had been hired to "improve" your property. The "preclaim notice of lien" must follow a very detailed format for a statement delivered directly to you. There is an example on the Washington State Department of Labor and Industries website. If the subcontractor didn't send you the notice or sent you an improper notice, he can't file a lien properly. If he tries to file the lien anyway, you can move to vacate the lien and can probably collect attorney fees for doing so. If the subcontractor did provide you with "preclaim notice of lien," then he may be able to file a lien properly, but enforcing it will require a Court action. He would have to foreclose on the lien within 8 months of filing the lien, which he would probably do in King County Superior Court. During that action, you could name the landscaper as an additional party responsible for the debt under the contract. It's essential your "lawsuit" against the landscaper under the same action the subcontract filed. Your landscaper was required to provide you with a "Disclosure Statement" as part of the documentation he gave you to start the work on your property. The "Disclosure Statement" must also follow a very detailed format. If he didn't send the notice or sent you an improper notice, then he won't be able to file and enforce a lien. There is an example of this document on the Washington State Department of Labor and Industries website, too. As you can see, there is are quite a number of issues surrounding and preserving your rights in an action for collection against you for work to improve your property. Good luck. Mark Arend.