Fit a battery smoke alarm to a concrete ceiling

Fit a battery smoke alarm to a solid concrete ceiling, with fixing methods for other ceiling types too.

AB-01Work out what your ceiling is made of and choose a spotTap the ceiling: a dull, solid thud with no give means concrete. A hollow sound that changes every 400-600mm means plasterboard on joists or battens underneath. Check an exposed edge in the loft or an unfinished cupboard to see if those joists are timber or thin metal C-section - a magnet sticks to steel, not timber. Pick a spot in the centre of the room or hallway ceiling, at least 300mm from any wall and away from light fittings, vents or a kitchen's cooking area.

1 each · Tape measure

Buy:ScrewfixB&QToolstationAmazon

AB-02Gather your tools and materialsFor concrete you need an SDS drill, not an ordinary combi drill - concrete will chew up standard bits fast. Lay a dust sheet below your working area. Set up your steps so you can reach the ceiling comfortably without stretching.

1 each · SDS drill

Buy:ScrewfixB&QToolstationAmazon

1 each · 6mm masonry drill bit

Buy:ScrewfixB&QToolstationAmazon

1 each · Dust sheet

Buy:ScrewfixB&QToolstationAmazon

1 each · Steps or small ladder

Buy:ScrewfixB&QToolstationAmazon

AB-03Do your safety checks before you drillRun a cable and pipe detector over the spot, but treat it as a warning, not proof - cables chased into concrete, run in conduit, or hidden above metal-backed board can be missed, and metal joists confuse cheap detectors too. Find your stopcock now (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 about what's behind that spot, switch off the relevant circuit at the consumer unit before you drill.

AB-04Drill into a solid concrete ceilingMark your spot with a pencil. Fit a 6mm masonry bit and set the SDS drill to hammer mode. Brace yourself squarely on your steps and drill straight up to a depth of 25-30mm, matching the length of your wall plug. Grey dust means you're in concrete - blow or vacuum the dust out of the hole before fitting the plug.

1 pack · Concrete wall plugs (pack of 10)

Buy:ScrewfixB&QToolstationAmazon

1 pack · 25mm screws (pack)

Buy:ScrewfixB&QToolstationAmazon

AB-05If your ceiling isn't concrete, fix it differentlyPlasterboard on timber joists: find the joist centre with a detector, drill a 3mm pilot hole straight into the timber, and drive a wood screw directly into it - no plug needed. If your spot lands between joists, don't rely on plasterboard alone; fit a proper toggle or hollow-wall anchor rated for a light alarm, or move the alarm a little to sit over a joist. Plasterboard on metal joists or battens: never use a plain wall plug or wood screw, they strip straight through 0.5mm steel; use a self-drilling metal-stud fixing or snap-toggle made for steel. Lath and plaster: aim for the joist behind the laths just as with timber, but drill your pilot hole gently, old lime plaster crumbles easily and can crack around the hole.

1 pack · Hollow-wall toggle fixings (pack)

Buy:ScrewfixB&QToolstationAmazon

1 pack · Self-drilling metal-stud fixings (pack)

Buy:ScrewfixB&QToolstationAmazon

AB-06Fit the mounting bracketHold the alarm's baseplate against the ceiling and screw it to your plugs or joist fixing. Tighten just enough to hold it firm - overtightening into old plaster can crack the surrounding area. Check the plate sits flat with no wobble before moving on.

AB-07Fit the battery and click the alarm into placeInsert the battery the right way round, matching the polarity marks inside the unit. Line the alarm up with its baseplate and twist it clockwise until it clicks and locks - most alarms won't sound without this final locking twist.

1 each · Smoke alarm (battery, 10-year sealed or 9V)

Buy:ScrewfixB&QToolstationAmazon

1 each · 9V battery (if not a sealed 10-year unit)

Buy:ScrewfixB&QToolstationAmazon

AB-08Test the alarmPress and hold the test button until you hear a loud, sharp beep. Step back and test again once the ceiling dust has settled, to make sure nothing is muffling it. An aerosol smoke tester is a good extra check if you have one.

1 each · Aerosol smoke alarm tester

Buy:ScrewfixB&QToolstationAmazon

AB-09Tidy up and record the fitting dateVacuum drill dust off the floor and any nearby surfaces, and fold away your dust sheet. Write the fitting date on the alarm casing if there's space, and set a reminder to test it monthly and replace a non-sealed battery once a year. If this is a rented property, check you meet the current legal requirement for smoke alarms.

RULES

KNOW THE RULES

In England, the Smoke and Carbon Monoxide Alarm Regulations require landlords to have a working smoke alarm on every storey used as living space. Check gov.uk for the current rules if you're letting the property.

Some links may earn us a small commission at no extra cost to you.

Save this as a project

Back to all guides