As applicable you must submit 2 sets of building plans, 3 sets of civil plans, and/or 3 sets of fire alarm or fire sprinkler plans.
Architects and engineers are required in accordance with State law. Architects are generally required to design projects where the area of work exceeds 4,000 square feet.
Engineers are required to design items not meeting the prescriptive requirements of the code where the practice of engineering is needed to demonstrate compliance, such as using a steel beam for a large wall opening in a house, roof trusses, or retaining walls. See RCW 18.43.010.