What are my options if landlord refuses to fix leaking roof?

For the past six years, I have been living in a room at the same premises as my parents, owned by my grandfather, for which rent is collected. The room is a single room with a leaking roof and no water or bathroom facilities. Despite asking them to fix it, they have dragged it on for six years with excuses and still haven't fully fixed it. Now they are denying responsibility, saying that I should fix it myself and that they don’t owe me anything.