In cases where your appraisal comes in below what you hypothesize to be fair, you don't have to lie down and take it. You can go to the lender and protest it, but you're going to need to be armed with documentation to support your argument. Be sure to include photos and a record of all improvements, as well as comps of other houses that should have been included. Your real estate agent should be able to look at the ones that were used for the appraisal and help you come up with better comps. You can also fork over the cash for your own appraiser and take that with you, if it comes in considerably higher than the first one.