EF-06Fix the new mounting points for your wall or ceiling typeCables and pipes can run almost anywhere in a ceiling void, including places you wouldn't expect. Use a cable and pipe detector, but don't trust it alone - it can miss deep cables, cables in metal conduit, or anything behind foil-backed plasterboard, and a metal frame confuses cheap detectors further. Find your stopcock (usually under the kitchen sink) and check it turns, so you can shut off water fast if you hit a pipe. If you have any doubt, isolate the circuit at the consumer unit before drilling, and turn off the water before cutting into anything that could carry water. Solid brick or block: drill a 6mm hole 35mm deep and use a red wall plug with a 40mm woodscrew. Timber joist or stud: drive a 4x40mm woodscrew straight into the centre of the timber, no plug needed. Metal stud: never use a wood screw or plastic plug, it strips straight through 0.5mm steel - use a self-drilling metal-stud fixing or a spring toggle rated for the fan's weight. Dot-and-dab: use a fixing long enough to pass through the plasterboard and adhesive dabs into the masonry behind, typically 50-75mm. Lath and plaster: locate a joist or batten behind the lath rather than fixing into the plaster alone, which will crumble. If the new unit is a heavier inline fan fitted separately in the loft, support it on a noggin or a proper pattress rather than plasterboard alone.