SR 18 closures coming as I-90 interchange project nears completion
Published 10:30 am Tuesday, April 21, 2026
After many years, the interchange improvement at State Route 18 and Interstate 90 is coming to a close, with final paving occurring soon.
The Washington State Department of Transportation (WSDOT) will have crews in the area for at least three upcoming separate closures for final paving and striping work. There will be two directional closures, followed by a full closure of SR 18 under I-90.
Paving was postponed due to weather, but if conditions are right, it will begin April 23, according to an April 20 update. For updates on road closures relating to this project, visit wsdot.wa.gov.
Each closure will start at 9 p.m. on a Thursday, and at least one lane of SR 18 will reopen at 5 a.m. the following Monday. The Tuesday before each weekend closure, one lane of SR 18 will close at 9 a.m. so crews can remove the guardrail.
Between the closures, one lane will remain closed so crews can re-install the guardrail and work on drainage.
After these directional closures, there will also be up to four weekend-long ramp closures, one for each direction of the I-90/SR 18 interchange.
When crews are done paving, there will be one more weekend-long closure to apply striping, which will “consist of a sequence of full directional closures and ramp closures of up to eight hours each, not occurring simultaneously,” according to a news release.
Detour options
During closures, drivers should follow signage dictating alternate routes and expect significant traffic delays. For real-time traffic information, visit wsdot.com/Travel/Real-time/Map.
Detours on Issaquah-Hobart Road and city streets in Issaquah are not suitable for truck drivers, who should use SR 169, I-405 or I-90 for all detoured travel.
Project timeline
While this series of closures will complete the diverging diamond interchange project at the intersection of SR 18 and I-90, it is not all of the SR 18 construction. WSDOT widened SR 18 from two lanes to four lanes between I-90 and Deep Creek, a section of about 2 miles, and is expected to complete that project in the late summer.
The widening of SR 18 from Deep Creek to Issaquah-Hobart Road is a separate project, with estimated completion in 2035. More information can be found at wsdot.wa.gov.
