It really depends on what the Architect is hired to do, how complex or thorough the documentation needs to be and the size of the job. Could be anywhere from 10% or even less to 20%+ of construction. Averages I have typically seen for not-too-involved residential remodel are in the 15% vicinity, but again: completely dependent on location, size and complexity. Best bet is to ask around locally and let the Architects tell you. You'll get a better sense of number AND a better sense of how the Architects work with you.