Smoke and heat alarms: what the law actually wants in your home (and your rental)

Smoke alarm rules are one of those subjects where everyone's half-sure and nobody's certain. One person read that interlinked alarms are now the law; another fitted a smoke alarm in the kitchen and can't work out why it screams every time they make toast. So here's the plain-English version for England. (Scotland has its own, stricter rules, since 2022 every Scottish home needs interlinked alarms throughout, but I work this side of the border, so everything below is England.)

The question everyone asks: "are interlinked alarms required in England?"

Short answer: it depends on whether building work is being done.

For a brand-new dwelling, a notifiable rewire, an extension or a loft conversion... yes. Building regulations (Approved Document B) expect mains-powered, interlinked alarms with battery backup, to at least the standard set out in BS 5839-6. "Interlinked" means when one goes off, they all go off... so an alarm in the loft wakes you in the bedroom. That's the requirement for new work.

For an existing home you're not doing building work on... no, interlinking isn't legally forced on you. It's strongly recommended, and if you're upgrading anyway it's a no-brainer, but there's no law making you retrofit it.

That's the confusion in a nutshell: interlinking is required when you do the work, not simply because you own a house. Get that distinction and most of the rest falls into place.

Owner-occupiers: what's law versus what's just sensible

If you own and live in your home and you're not touching the electrics, the honest position is that the law mostly leaves you alone... the strong recommendation is that you have working alarms, but nobody's coming to inspect your landing.

The moment that changes is when you do notifiable electrical or building work. Do a rewire, replace the consumer unit as part of bigger works, extend, convert the loft... and the alarm requirements come with it. At that point I'd be fitting a mains-powered, interlinked system with battery backup, which in the standard's language is a Grade D system, and deciding the coverage (the "LD" category) with you... circulation spaces as the minimum, ideally the main rooms too.

Even where it isn't strictly required, a rewire is the sensible time to do it. The cables are already going in.

Sealed 10-year battery vs mains-powered

Two honest options where hardwiring isn't on the cards:

• Mains-powered (hardwired) with battery backup... the gold standard, and what goes in with new work. Wired in, interlinked, backup battery for power cuts. Fit and largely forget.

• Sealed 10-year battery alarms... self-contained, no wiring, and the battery lasts the life of the unit (you replace the whole alarm after ten years, not the battery). A perfectly respectable choice for an existing home where chasing mains cable into finished walls would mean tearing the place up. You can even get these interlinked wirelessly now.

What I'd steer you away from is the old removable-9V-battery type... the ones that get silenced at 2am and never reconnected. If yours takes a battery you swap out, it's living on borrowed time.

Where each alarm actually goes... heat, smoke and CO

This is where the kitchen-toast problem comes from. Different sensors belong in different rooms:

• Kitchen: a heat alarm, not a smoke alarm. Smoke alarms and cooking are natural enemies... put an optical smoke alarm near the hob and it'll cry wolf until someone rips the battery out, which defeats the whole thing. A heat alarm triggers on a genuine rise in temperature, not on your grill.

• Hallways and landings: smoke alarms. Circulation spaces, the routes you'd escape down, are the priority, one per storey. This is the minimum everyone should have.

• Living rooms and main rooms: smoke alarms if you're going for fuller cover.

• Carbon monoxide: near fuel-burning appliances. A CO alarm is a different animal entirely... it detects a gas you can't smell, not smoke. It belongs in any room with a fixed combustion appliance: a gas boiler, a wood burner, an open fire, an oil boiler. (A gas cooker is the odd exception the rules leave out... though I'd never talk you out of one near a gas hob anyway.)

The other placement myth: don't tuck a smoke alarm right up against the kitchen or bathroom door to "cover" it. Steam and cooking fumes both set optical alarms off. Give them a bit of room.

Landlords in England: the rules are firmer

If you let property, this stops being a recommendation and becomes the law... the Smoke and Carbon Monoxide Alarm (England) Regulations. In every rented home in England you must have:

• At least one smoke alarm on every storey that has a room used as living accommodation.

• A carbon monoxide alarm in any room used as living accommodation that has a fixed combustion appliance (boiler, wood burner, solid-fuel fire) again, gas cookers excepted.

• Every alarm proven to be working at the start of each new tenancy. That's your job as landlord on day one, not the tenant's.

Interestingly, the rental rules don't force mains power or interlinking... a working battery alarm on each storey satisfies the letter of the law. Enforcement is a remedial notice first, and a penalty charge of up to £5,000 per breach if it's ignored. (That's separate from the electrical/EICR penalties, which are a different regime... I've written about the EICR side elsewhere.)

If you're a Slough landlord with an HMO, be aware that houses in multiple occupation carry stricter fire-detection expectations than a single let, often a more comprehensive interlinked system, so don't assume the basic "one per storey" covers you there. Worth confirming per property.

Test them... properly, and often

Whatever you've got, press the button. A smoke alarm is only as good as the last time you checked it worked: once a month is the habit to get into, and it takes ten seconds. Interlinked systems let you test that the link works too... press one, they should all sound. If they don't, something's not talking to something.

The natural moment to hardwire

If you're already having a full rewire or a new consumer unit fitted, that's the moment to put in a proper mains-powered, interlinked alarm system while everything's accessible... you'll never have a cheaper or tidier opportunity to do it. Retrofitting later always means more mess.

Not sure what your home or your rental actually needs... or whether what you've got is up to standard? I'll take a look and tell you straight, no obligation. Book a free quote at https://bphelectrics.co.uk/ or call +44 7722 132736. I'm a NAPIT-registered, family-run electrician covering Slough, Windsor, Maidenhead and the wider Thames Valley.