We hired someone to build a cement stock tank type swimming pool. After he finished the job, we found lots of problems. The plumbing and skimmer is not going to be usuable at all without us breaking cement and redoing. The cement work is terrible. The bottom is so rough you can hardly walk on it. We stopped payment on his last check and would like to have someone else fix our pool. Are we obligated to pay him any more? We have paid him about 80% of the amount he charged. No signed contracts involved.