I don't know about other areas, but in Columbia, SC the listing agent has a fiduciery responsibility to their Seller client to verify square footage of the home when it is listed. The listing agent should provide a sketch addendum (drawing with square footage) with the other listing documents submitted to MLS and/or their broker. The Listing Agent is representing that the square footage is accurate within plus or minus 10%. Realtors are not Appraisers so small errors or getting as close as possible in their measurements is realistic. If you hired a Realtor to help you purchase your home in Columbia, your Realtor also has a fiduciery responsibility to you to verify information on the listing.
I know the popular idea is Buyer beware and it's the buyer's responsibility to verify everything....The contract does have all that disclaimer information already mentioned, so it is easy to understand why Realtors may think that the Buyer has the burden. I personally would not want to explain all of these ideas about buyer beware to a jury of my peers after the opposing attorney has just explained my commision to them.
To answer your question...If you financed your home, it is likely that an appraisal was done. Most lenders will provide you with a copy, especially if you ask for it, but they don't have to share it with you. Most people are not aware that the Lender or the Bank is the Appraiser's client and the Appraiser will not provide a copy to anyone other than their client and the Bank is not obligated to give you a copy.
If you don't have access to an appraisal and your Realtor is not able to assist you in verifying square footage, you can contact an Appraiser to measure your home. Many Appraisers will measure a home for $50 to $75 and provide you with a sketch to show how that square footage was calculated.
It may be that the Realtors did verify square footage and made a mistake or you may not understand how square footage is calulated in this area. It may be a good idea to talk with your Realtor first to get some answers. If there is an issue, an attorney can advise you about options.
Let me know if you need contact information for an Appraiser to measure square footage.
Tina Ormerod, Realtor
Also if you used the "Offer to Purchase" contract revised 07/06 developed by the Greater Columbia Association of Realtors. Note the Disclaimer in Section 33: it states: "The parties acknowledge that the listing and selling broker(s) and their agent(s) ... (B) Give no warranty, express or implied, concerning the conditions of the property, ... or the accuracy of the square footage heated or unheated...." By the way a new Offer to Purchase contract have been developed by our local SC REALTOR's - Central Carolina Realtors, in effect this 10/1/08.
Consult an attorney if you still have questions or concerns.
You should see the source quoted for the measurement (usually the County Assessor's office).
Go to the local City Dept. of Building and Safety and ask to see the building permits for your property.
Also, an architect could measure the square living area of your home, they'll need to make a scale drawing.
Then you should discuss with the Realtor who represented you.
If it is important for you to know I would recommend hiring someone to measure. At this point, however, there is really nothing that can be done even if your home measures less that the 1945 square feet. Good luck!