Smoke Alarm Installation Guide UK¶

Step-by-step guide to installing smoke alarms in UK homes to comply with BS 5839-6 and Building Regulations Approved Document B.

Choosing the Right Smoke Alarm Type¶

UK regulations under BS 5839-6 recommend Grade D1 mains-powered interlinked alarms with battery backup for most homes. Prices range from £15 for a basic battery-only unit to £45 for a mains-powered Aico alarm. For new builds, Grade D1 is mandatory. Optical sensors are preferred for escape routes and hallways, while ionisation alarms suit landings. Aico and FireAngel dominate the UK market, with Ei Electronics offering competitive options. Heat alarms are required in kitchens to prevent false alarms. Installation height should be ceiling-mounted at least 300mm from walls and light fittings.

Step-by-Step Installation Process¶

Start by turning off the mains supply at the consumer unit. Mark the ceiling position ensuring 300mm clearance from corners. For mains-powered units like the Aico EI146, drill holes for rawl plugs, mount the backplate, and connect to the 230V supply via a 3-core flex. Push-fit connectors simplify wiring. Insert the backup battery (typically a 9V or sealed lithium cell), clip the alarm head onto the base, and restore power. Test using the hush button. Battery-only models require only screws and plugs - no electrical work needed. Always follow the manufacturer's instructions and consider hiring a qualified electrician for hardwired installations.

Specifications and Comparison¶

Alarm Type	Best Location	Price Range	Standard
Optical Smoke	Hallways, landings	£15-£40	BS 5446-2
Ionisation Smoke	Stairs, landings	£10-£25	BS 5446-1
Heat Alarm	Kitchen, garage	£20-£35	BS 5446-2
Combined CO/Smoke	Near bedrooms	£30-£65	BS 50291

FAQ¶

How many smoke alarms do I need in a 3-bed house?: BS 5839-6 recommends at least one alarm on every floor, plus a heat alarm in the kitchen - typically 4-5 units for a standard 3-bedroom home.
Can I install smoke alarms myself in the UK?: Yes, battery-powered alarms are DIY-friendly. Mains-powered installations should be carried out by a Part P qualified electrician unless you are competent and confident.
Do smoke alarms need to be hardwired in new builds?: Yes, Building Regulations Approved Document B requires mains-powered interlinked alarms with battery backup (Grade D1) in all new-build properties. For more information see our Heat Alarm Installation Guide UK.

Last updated: 2026-05-31.

External Resources¶

For further information consult authority guidelines at the British Standards Institution (BSI).