This is all so they can make good comparisons, you don't want to compare an apple to an orange even though they are both a piece of fruit!
In different parts of Anchorage where the homes were built in the 50's - 70's many of them had no garage but did have a carport. Quite often the owners would enclose the carport and install a door. Sometimes they insulated and sheet rocked them, sometimes not. It's a good idea to have you're Realtor and home inspector investigate this if it's an older home in a long standing established neighborhood.
In Anchorage I've been seeing about $8,000 per additional car bay when it's an actual attached heated garage. NOTE: This is not the same as the difference between having a garage and having no garage, whether it's 1, 2 or 3 bay.
If you would like my "Cheat Sheet" of standard appraisers adjustments which I have compiled using many appraisals from my successful sold listings, just email me at email@example.com and put Appraisers Cheat Sheet in the subject line, or call me at 907-223-8422.
Mark Mandigo is a licensed Real estate professional and a REALTORÂ® for the State Of Alaska
http://www.mandigomanor.com you can visit his Blog at http://anchorageliving.wordpress.com