When we bought our house several years ago, we noticed a small crack in the ceiling/corner of a window frame of one of the bedrooms and thought it was likely to be old plaster (house in 1930s) and would need redone at some point, but it's got gradually worse and I'd really like to get someone to check it out to make sure we don't have a structural issue. Would a builder be the best trade to advise or a structural engineer? And should we be doing it via insurance in case there is a major problem?