I find it hard to believe that you live in a 12 year old townhouse that has no association associated with it. It would be very surprising if the local authorities allowed that to happen.
I think you should contact your local property registrar (recorder? clerk?) and ask them to see if in fact you are in an association. They should be able to do that from your address. If that doesn't work, I think you need to talk to an attorney.
If that doesn't work, seek an attorney.
In either event, talk to your neighbor about your concerns. That is the best solution to these problems.
My advice, of course, is general and based on very little knowledge of your personal situation, and I am licensed to practice law only in Idaho, Utah and Wyoming. You should retain legal counsel and review you situation with him or her, if it has significant financial or other implications. <a href="http://www.haolaw.com" target="_blank">Visit www.haolaw.com!</a>
I don't disagree with Mr. Hobbs, but often Associations won't get involved in matters between two neighbors that have no affect on the Association or common areas.
I also agree that you need to speak to your neighbor, who may be as oblivious as you were about what's going on up on the roof. First I would suggest you check the covenants (if there is an association) and verify who is responsible for roof/gutter repair and maintenance. Take that with you when you go to speak with your neighbor, along with any contractor's reports about what occurred, how it occurred and how it needs to be fixed. Photos may be helpful, as well. You certainly should ask your neighbor to provide his insurance information so you may make a claim against his homeowner's policy. If he doesn't have a homeowners policy, you may want to ask the Association (if there is one) if their policy offers water damage coverage and if you can use it (presuming you pay assessments that allow them to purchase the coverage). But be aware that in Georgia, policies that offer water damage coverage usually have unbelievably high deductibles, and your nighbor may find it cheaper to make the repairs/pay for the repairs than paying the deductible.
If your neighbor doesn't like what he's hearing and wants to argue, don't fight it or argue. Instead, see an attorney and prepare to take him to court if the repair costs are too high. You may have to take such action anyway if he won't make the gutter repair, because anything you do to fix the interior will be damaged again after the next rain/snow if the gutters aren't fixed...
This is not intended to be legal advice or create an attorney-client relationship. If more information is needed, you should consult with an attorney in your state regarding the specifics of your situation and the options available to you.
Although it may be late to inquire, there may be original contractor liability here. And your neighbor may also have damage in the common wall. It is good advice to talk to your neighbor as soon as possible. Invite him over for tea and cookies, and to view your damage, and your estimates to fix it. And you do need to do your property and HOA legal research. If you feel overwhelmed by it all, consulting a local real estate lawyer may help sort things out. But you should contact your neighbor in person before sending in the lawyers.
DISCLAIMER: The forgoing comment is for general educational purposes only, and is not legal advice upon which the reader may rely as the commenter has no actual knowledge of the facts of the case, has not interviewed persons or examined evidence, and has not researched the applicable law. The comment is based only on the facts provided, which are extremely limited, and may or may not be true. Complete defenses may prevent the success of any claim. Competent legal advice should always be obtained before taking any legal action or filing suit. Readers employ any information provided herein at their own risk.