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Who's paying that architect? If it's not the Owner, he/she can be ignored since the Contractor is working for the Owner and the Owner agreed to your punch list. And were the items on the punch list defined in the drawings and specs? If the documents were unrealistic, the Contractor has had plenty of time to say so during construction.
And yes, it looks unethical to me. Potentially illegal if he didn't have a written contract before doing his work – at least in the states where I've practiced – CA, OR, WA.
Certainly not nice. Unethical? depending on the information provided to the other architect.
Do the items on the punch list not conform to specifications/drawings? Did the other architect see the contract documents prior to commenting (did the contractor hoodwink an opinion by implying standards not provided). Did the contractor tell the other architect that an architect was involved.
Most important, what is the business, or other relationship between the contractor and the other Architect?
And finally; without permission the other architect is trespassing, assuming the punch list was associated with substantial completion, and the contractor did not tell the architect that he did not have the authority to invite him into the property (architect misinformed rather than ignorant).
Contractor bringing in another architect is irrelevant. He has an agreement with owner to perform and you as architect are responsible for punch list. Do pay till work is completed.
Sean J Bujold, AIASean Bujold & Associates, Inc.