The Role of a Relevant Building Surveyor: Ensuring Compliance and Safety in Domestic Projects

I’ve been going through the process of planning a small extension at home and keep running into questions about what exactly a relevant building surveyor does beyond just checking drawings. Some people told me they only show up for inspections, others say they’re deeply involved right from the permit stage. For a domestic project, especially when you want to make sure everything is compliant and safe, how far does their responsibility actually go? Do they help avoid mistakes, or is it more like a final stamp of approval?