It all depends on the wording in the contract. Most contracts state that the house is being sold as-is, meaning it should be in the same condition as is was when the buyer viewed the house. A normal contract of sale usually would also guarantee and represent that the electrical system, heating system and plumbing system be in working order and free of leaks. In addition, usually the roof is guaranteed to be free of leaks. This is only up until the closing. Once the closing is finished, any problems are now the new buyers headache. A typical contract does not make any warranties after the closing. Because of this, the buyers do a "final walk-through" the day of or before the closing to make sure that the house is in the same condition as it was when they last saw it.
If the condition had been changed, as would be the case in your example, the seller would have to fix or give financial consideration to the buyers if the contract was worded on the "normal" fashion (here in Brooklyn at least). If your contract was not worded in the "normal fashion, you may have no recourse. As an example, when someone purchases a foreclosure property, most of the time the property is being sold strictly as-is, meaning that you have to take it in whatever condition it is in at the time of the closing and you do not get any warrrantees or guarantees at all. The other extreme is when you are dealing with new construction... with new construction, the seller must give the buyers a full one year warrantee on virtually everything in the house!
So in order to answer your question, you need to know how your contract is worded. Your lawyer should be helping you with all of this.
One more thing, often times it is very hard to prove that the condition has changed, if you do not have concrete evidence to support that, you will not win in a court of law. Please bear in mind that I am not an attorney and I cannot give legal advice, this answer is just my humble opinion after being in the real estate business since 1993. You must speak to your attorney.
Mitchell S. Feldman
Associate Broker/ Director of Sales
Madison Estates & Properties, Inc.
Office: (718) 645-1665/ Cell: (917) 805-0783