No, he cannot: doing work on a house, making additions or renovations to, even contributing money to does NOT give him any right to or interest in the home unless there had been a written agreement in place, prior to him doing the work, that in exchange for what he did, he would get an interest in the home (essentially, that he was buying an interest with his work). Doing something voluntarily (of your own free will) to benefit a person (or to benefit yourself: if was living there, he received the benefit of improvements, too, since it made his living situation better) doesn't let you claim their property unless you agreed to give them a claim.