AB-02Work out what's behind the tilesTap the tiled wall in several places. A dull, solid thud usually means solid brick or block, or plasterboard bonded tight to the wall with dot-and-dab adhesive (common since the 1990s). A hollow, drum-like sound means a timber or metal stud wall, with solid strips roughly every 400-600mm where the studs sit — run a stud detector or a strong magnet along the wall to find them, since screw heads under the board give regular clicks. Drill a small 3mm pilot hole somewhere already loose or hidden: pale, fine dust means a timber stud, grey metallic swarf means a metal stud, and a soft crumbly give with no resistance suggests lath and plaster (common before about 1930). Cables and pipes can run almost anywhere behind a tiled wall, especially near sinks, showers and baths, so treat every wall as live and full of pipework until you've proven otherwise — a detector helps but can miss cables that are deep, in metal conduit, behind metal-backed board, or thrown off by a metal stud frame. Before you drill, find your stopcock, usually under the kitchen sink, and check it turns freely so you can shut the water off fast if you hit a pipe. If you have any doubt at all, isolate the relevant circuit at the consumer unit first.