Usda, if you feel so inclined to, check with an attourney. This has all the makings of a civil lawsuit for fraud, failure to disclose, or at the very least misrepresentation. Hell, because of the nature of the stairs alone, you or your family could have recieved serious bodily harm. Hell, there may even be criminal charges.
You may not have had the written agreement done, but you did have a verbal contract. Never hurts to ask questions, unless you have already done so.
Hope things work out for you in the long run.