Wash. Rev. Code § 11.56.040
If the court should determine that it is necessary or proper, for any of the said purposes, to mortgage any or all of said property, it may make an order directing the personal representative to mortgage such thereof as it may determine upon, and such order shall contain the terms and conditions of such transaction and authorize the personal representative to execute and deliver his or her note or notes and secure the same by mortgage, and thereafter it shall be the duty of such personal representative to comply with such order. The personal representative shall not deliver any such note, mortgage, or other evidence of indebtedness until he or she has first presented same to the court and obtained its approval of the form. Every mortgage so made and approved shall be effectual to mortgage and encumber all the right, title, and interest of the said estate in the property described therein at the time of the death of the said decedent, or acquired by his or her estate, and no irregularity in the proceedings shall impair or invalidate any mortgage given under such order of the court and approved by it.
RCW 11.56.040