Lets look at the bigger picture. What will the buyer be solely responsible for concerning maintenance, repair & replacement? What is the home owner association responsible for? These questions should be answered by the RE Agent. The patios are a construction defect and It would be my guess that they fall under the HOA's responsibility. This still would affect the individual owners as each owner would have to pay their portion of the repair bill and costs of litigation against the builder. I would report this as a construction defect that will affect the buyer solely or as a member of the owners association. The buyer should consult with the agent as to who is responsible for the repair. The seller, in a perfect world should be taking care of the repair by themselves or through the HOA.