Depending on the circumstances of the case, the roofing company can claim that they reasonably relied on your promise to give them the job and that they suffered damages (spent money on materials, hired workers, declined other contracts, etc.) because of your cancelling out the agreement with them. There are ways to defend against such claim, but it is not a good idea to try doing it yourself. If they already served you with a complaint that was filed with the court, retain an attorney. If they haven't yet, ask them directly what damages do they claim and why, and see whether their answer sounds reasonable enough to convince you to pay. If not, wait and see whether they will, in fact, take you to court (often, the threats to sue are just a bluff). If they will, retain an attorney, don't wait until you lose the case and have to do an appeal.
Answered on Sep 28th, 2012 at 12:33 AM