Interlinked Smoke Alarms: Costs, Installation and Who Needs Them
By the DC Fire & Security engineering team — installing and maintaining fire and security systems since 2010. Updated June 2026.
Quick answer
Interlinked alarms — when one sounds, all sound — come two ways: sealed 10-year radio-linked (£40–£70 per alarm, fit-anywhere, the retrofit standard) and mains-wired interlinked (new-build/rewire territory). A typical 3-bed house interlinks for £150–£300 DIY or £250–£500 professionally fitted. Scotland mandates them in all homes; England requires them in new builds and (effectively) HMOs.
Why interlinking matters (the 3am physics)
A fire in the kitchen at 3am has filled the hallway before a closed-door bedroom's occupant hears anything from a standalone alarm downstairs — sleep, doors and distance eat single-alarm warnings. Interlinked systems collapse that delay: the kitchen heat alarm's trigger sounds the bedroom alarms simultaneously, buying the minutes evacuation actually needs. Research behind Scotland's universal mandate made exactly this case. Placement logic (which rooms, what types — heat in kitchens, smoke on routes/living rooms) lives in our placement guide; interlinking is the multiplier on whatever you place.
The two technologies and what they cost
| Sealed radio-linked (RF) | Mains-wired interlinked | |
|---|---|---|
| How they link | Wireless RF between units | Interlink cable (or RF-capable mains units) |
| Power | Sealed 10-year lithium | Mains + backup cell |
| Fits | Any existing home — no wiring | New builds, rewires, major refurbs |
| Unit cost | £40–£70 (smoke/heat) | £25–£50 + wiring labour |
| 3-bed house (4-5 units) | £150–£300 DIY / £250–£500 fitted | Trivial in new-build electrics; £400–£800 retrofit |
| Lifespan | 10 years, replace whole unit | 10-year heads on permanent bases |
| Compliance fit | Scotland-compliant, HMO-accepted by most councils (verify), landlord-friendly | BS 5839-6 Grade D1 — new-build standard |
Who must, who should, and buying notes
Must: Scottish homes (all — the post-2022 law: interlinked smoke in living room + circulation each storey, heat in kitchen); English new-builds (Grade D1 wired via Building Regs); HMOs (interlink expectations throughout licensing schedules — the HMO spec guide details grades). Effectively-must: English landlords replacing/upgrading (per-storey alarms are the legal floor — see the landlord rules — but interlinked sealed units cost little more and end battery disputes); anyone with sleeping floors above living floors. Should: honestly, everyone — £200 of RF alarms is the cheapest life-safety upgrade in housing. Buying notes: stick to major brands (Aico's RadioLINK ecosystem dominates professional fits; FireAngel/Kidde serve DIY well), match RF families (links are brand-ecosystem-specific), date-check stock (10 years runs from manufacture), and for landlords/portfolios we fit and certificate at scale — per-property records included, the compliance-file way.
Frequently Asked Questions
Do interlinked alarms work through thick walls/floors?
Can I mix smoke and heat alarms on one interlink?
Mains-wired or sealed RF for my 1990s house?
Do they really last 10 years untouched?
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