Wash. Rev. Code § 4.16.310
All claims or causes of action as set forth in RCW 4.16.300 shall accrue, and the applicable statute of limitation shall begin to run only during the period within six years after substantial completion of construction, or during the period within six years after the termination of the services enumerated in RCW 4.16.300, whichever is later. The phrase "substantial completion of construction" shall mean the state of completion reached when an improvement upon real property may be used or occupied for its intended use. Any cause of action which has not accrued within six years after such substantial completion of construction, or within six years after such termination of services, whichever is later, shall be barred: PROVIDED, That this limitation shall not be asserted as a defense by any owner, tenant or other person in possession and control of the improvement at the time such cause of action accrues. The limitations prescribed in this section apply to all claims or causes of action as set forth in RCW 4.16.300 brought in the name or for the benefit of the state which are made or commenced after June 11, 1986.
If a written notice is filed under RCW 64.50.020 within the time prescribed for the filing of an action under this chapter, the period of time during which the filing of an action is barred under RCW 64.50.020 plus sixty days shall not be a part of the period limited for the commencement of an action, nor for the application of this section.
RCW 4.16.310
Preamble-Report to legislature-Applicability-Severability-1986 c 305: See notes following RCW 4.16.160.