Three things, and a file stalls when any one of them is missing.
Independence. The appraiser cannot have an interest in the transaction. That is why a value supplied by the party who wants the loan is rarely accepted on its own.
A defined basis of value. Market value, as of a stated effective date, with the approach used set out in full. A number with no reasoning behind it cannot be reviewed.
A recognised standard. Reports written to CUSPAP, the Canadian Uniform Standards of Professional Appraisal Practice, by an appraiser holding a designation from the Appraisal Institute of Canada. Our appraisers hold AACI and CRA designations.
One thing worth understanding before you start. Lenders size the loan against the appraised value, not against the price you agreed. If the appraisal comes in below the purchase price, the shortfall comes out of your down payment, not the lender’s advance.