Wash. Rev. Code § 8.28.040
Whenever in any eminent domain proceeding, heretofore or hereafter instituted for the taking or damaging of private property, a verdict shall have been returned by the jury, or by the court if the case be tried without a jury, fixing the amount to be paid as compensation for the property so to be taken or damaged, such verdict shall bear interest at the maximum rate of interest permitted at that time under RCW 19.52.020 from the date of its entry to the date of payment thereof: PROVIDED, That the running of such interest shall be suspended, and such interest shall not accrue, for any period of time during which the entry of final judgment in such proceeding shall have been delayed solely by the pendency of an appeal taken in such proceeding.
RCW 8.28.040