We are having a house built that was supposed to be done in Sept and it still isn't done. We want to sue for breach of contract. Do we have a case?

You certainly have the right to expect that your contractor will adhere to the terms of your agreement.  Whether you have a case depends on the facts and the contents of your contract.  Other factors will need to be considered to develop a list of your options that will get your issue solved quickly and with the least amount of cost.  Suing the contractor isn't always the best solution but sometimes it's what's necessary.  You should contact an attorney in your area to review the details and get some specific advice.