The major sub-contractors should also agree with the selection. The SN’s role should be decided by the parties up front, but essentially he is to be called upon as soon as any problem or dispute arises. He should make a site visit and meet with all parties involved in the dispute including the Architect.
The SN should make a decision to resolve the dispute as soon as practicable – sometimes within hours. The idea is to resolve problems before they get out of hand. He should initially attempt to facilitate a settlement, but failing that he should render a final, binding decision.