Refix a light switch that's loose in the wall

Turn off the power, work out what's behind the wall, then refit the switch with the right fixing and test it.

LS-01Turn off the power and prove it's deadSwitch off the circuit at the consumer unit for the lighting circuit involved, then prove it's dead at the switch using your voltage tester before touching any wires. Leave a note or ask someone to stay by the consumer unit so nobody switches it back on while you work. Don't rely on the wall switch itself being off — always isolate at the consumer unit.

LS-02Know what's behind the wall before you drillCables and pipes can run almost anywhere, not just in obvious straight lines, so use a cable and pipe detector before you drill or deepen any fixing holes — and still treat the area as live until you've proved otherwise. Cheap detectors can miss deep cables, cables in metal conduit, cables behind metal-backed plasterboard, and they get confused by metal stud frames. Find your stopcock now (usually under the kitchen sink) and check it turns, so you can shut off water fast if you ever hit a pipe. If you have any doubt, isolate the circuit at the consumer unit before drilling, and turn off the water at the stopcock before cutting into anything that could carry a pipe.

LS-03Remove the faceplate and check the boxUndo the two fixing screws holding the switch faceplate and gently pull it away from the wall, keeping the wires attached. Look at how the box is fixed to the wall — check for cracked plastic, stripped screw threads, a loose plaster patch, or a box that's come away from its lugs entirely. This tells you what's actually failed before you start re-fixing anything.

1 set · Insulated screwdriver set

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LS-04Work out what kind of wall you're fixing intoTap around the box: a dull, solid sound usually means brick or block, a hollow sound means plasterboard on studs or dot-and-dab. Run a stud detector or a strong magnet across the wall near the box, looking for a line of screw heads — timber studs are usually 400mm or 600mm apart. Drill a small 3mm pilot hole in an inconspicuous spot nearby: fine pale dust means timber, shiny metal swarf means a metal stud, and solid resistance with brick-coloured dust means masonry.

1 each · Stud and cable detector

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LS-05Fixing into solid brick or blockIf the fixing holes have crumbled or stripped, drill new ones 20mm away using a 6mm masonry bit to 35mm depth, then tap in new wall plugs. Screw the box back in with new 4mm x 30mm screws, tightening until firm but not overtight — overtightening can crack the plaster around the box.

4 each · Wall plugs (red, 6mm)

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4 each · Wood screws 4mm x 30mm

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1 each · Masonry drill bit 6mm

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LS-06Fixing into a timber stud wallIf the box is fixed to a timber stud or a noggin, screw straight into the centre of the timber with a wood screw — no plug needed. If the original screw hole has worn oversized in the wood, move the screw 10-15mm to one side into solid timber rather than reusing the stripped hole.

2 each · Wood screws 4mm x 30mm

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LS-07Fixing into a metal stud wallNever use a plain wall plug or an ordinary wood screw in a metal stud — it strips straight through the thin steel and the box will just work loose again. Use self-drilling metal-stud screws for a direct fix, or a metal-rated toggle fixing if you're fixing into the plasterboard between the studs rather than the stud itself. A light switch is light enough for these fixings; anything heavier pulling on the wall would need a timber noggin fitted behind it instead.

4 each · Self-drilling metal stud screws

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LS-08Fixing into dot-and-dab plasterboardOn dot-and-dab walls the plasterboard sits on blobs of adhesive with a gap behind it, so short screws just spin in fresh air once the board flexes. Use fixings long enough to pass through the plasterboard and the gap and bite into the masonry behind — typically 60-75mm — or fit a dry-lining box with spring-out legs if you can't reach solid backing. Check the depth by gently probing the existing hole with a screwdriver before choosing your fixing length.

4 each · Long masonry screws 70mm

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1 each · Dry-lining box with legs

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LS-09Fixing into lath and plasterLath and plaster is brittle and the old laths can crumble if you overtighten a screw. Find the timber lath or a batten behind the box with a bradawl, use shorter, finer screws than you'd use in plasterboard, and stop as soon as the fixing feels snug. If the plaster around the box is loose or crumbling, it's worth patching it with a small amount of filler once the switch is refitted.

4 each · Fine wood screws 3mm x 25mm

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1 small tub · Multi-purpose filler

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LS-10Fit a new mounting box if the old one is damagedIf the box itself is cracked or the fixing lugs have snapped off, replace it rather than trying to reuse it. Match the new box to the wall type — a metal or plastic box for masonry and stud walls, or a suitable dry-lining box for dot-and-dab — and fix it using the method for your wall type above before reconnecting anything.

1 each · Plastic single switch box, 25mm deep

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LS-11Reconnect the switchReconnect the wires to the terminals exactly as they were before, checking each one is tight in its terminal with a gentle tug. Refixing a switch like this doesn't need to be notified under Part P, because you're not adding a new circuit — but if the switch is in a bathroom, take extra care about its position relative to the bath or shower.

RULES

KNOW THE RULES

Part P of the Building Regulations covers electrical safety in England. A like-for-like switch refix isn't notifiable, but special rules on positioning near water apply in bathrooms.

LS-12Screw the faceplate back on and testFold the wires neatly into the box and screw the faceplate on evenly, tightening both screws a little at a time so the plate sits flush and square. Restore power at the consumer unit, then flick the switch to check the light works and the plate feels solid with no wobble.

LS-13Tidy upVacuum any drilling dust from the floor and skirting, and wipe down the wall around the switch. Put spare screws and plugs back in your toolbox for next time, and dispose of any broken box or offcuts.

1 each · Dust sheet

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