Breach of Trust

Hi Sir, We have started constructing a house in January-2015 without any service agreement with Engineer (we didn't signed any contract or agreement since the Engineer was known person to us and our friend and this was mutually agreed). However he breached our trust by delaying the construction work by providing irrelevant justifications. Its been 14 months now but only 70% of the construction work is completed. Because of this delay we are extending our stay at rented house and also underwent lots of personal trauma and pain. Now we do not want to continue with him as also we noticed that he has rigged few of old bills (by charging high material and labour cost- we have certified this with new Engineer). we are continuing the construction work with the help of new Engineer now. In the meantime we have kept few of his old bills pending as we felt that he has cheated us by rigging the old bills. So does he have any chance of filing case against us and if he does so- how should we defend in turn through legal way as we didn't signed any agreement with him.