CT-02Check for cables and pipes, then work out what's above the plasterboardBefore you drill anything, run a cable and pipe detector along the whole marked line, in both directions. Still treat the ceiling as if something could be there even with a clear reading - detectors can miss cables in conduit, deep in the void, or behind metal-backed board. 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're at all unsure, isolate the room's circuit at the consumer unit before drilling. Then track along the line with the detector or a magnet - dimples or screw heads every 400mm or 600mm mean timber or metal joists above, and a dull, solid knock everywhere means a concrete soffit. Drill one 3mm test hole where a bracket will sit: pale wood dust means timber, fine grey swarf means a metal furring channel or resilient bar, and hard resistance with brick-red dust means concrete. In houses built before about 1930 the ceiling may be lath and plaster - the test hole will show thin wood laths with gaps behind old lime plaster, and it crumbles more easily than modern plasterboard.