Wash. Rev. Code § 8.04.112
If there is a building standing, in whole or in part, upon any land to be taken, the jury shall add to their finding of the value of the land taken, the damages to the building. If the entire building is taken, or if the building is damaged, so that it cannot be readjusted to the premises, then the measure of damages shall be the fair market value of the building. If part of the building is taken or damaged and the building can be readjusted or replaced on the part of the land remaining, and the state agrees thereto, then the measure of damages shall be the cost of readjusting or moving the building, or the part thereof left, together with the depreciation in the market value of the building by reason of such readjustment or moving.
RCW 8.04.112