Hardwired Interlinked Smoke Alarms in Wales: What Landlords Must Install

Battery Alarms Do Not Comply in Wales

This is the single most common mistake Welsh landlords make with fire safety. Regulation 5 of the Renting Homes (Fitness for Human Habitation) (Wales) Regulations 2022 requires smoke alarms that are:

1. Hardwired into the dwelling's electrical supply
2. Interlinked so that when one alarm activates, every alarm in the property sounds
3. Installed on every storey that contains a habitable room, hallway, or landing

Standalone battery-powered smoke alarms — even long-life lithium units — do not satisfy the regulation. If your rental property in Wales has battery alarms, it is automatically treated as unfit for human habitation under Section 91 of the Renting Homes (Wales) Act 2016.

The applicable standard is BS 5839-6 Grade D1: mains-powered detectors with integral battery backup, connected to a shared circuit so they interlink across all floors.

Where Exactly Do They Go?

A smoke alarm must be present on every storey of the dwelling that has a habitable room, a hallway, or a landing. In practice, that means:

• Ground floor: hallway or landing near the kitchen. A heat alarm may be used in the kitchen to reduce cooking-triggered false alarms; the regulations do not make a kitchen heat alarm part of the every-storey smoke-alarm rule.
• First floor: landing or hallway serving the bedrooms
• Second floor and above: same rule applies for every additional storey

A two-storey house needs at least two interlinked smoke alarms. A three-storey converted flat needs three. If a loft conversion creates a habitable room, that storey needs coverage too.

Carbon Monoxide Alarms: Different Rules

CO alarms follow a separate standard. Under the same Regulation 5, a carbon monoxide alarm must be fitted in every room containing a fixed combustion appliance — boilers, gas fires, log burners, gas hobs, and oil-fired heaters all count.

The CO alarm standard is BS EN 50291. Unlike smoke alarms, CO detectors can be powered by a sealed long-life battery or mains-hardwired. There is no statutory requirement for CO alarms to interlink, though interlinking them is good practice in larger properties.

Key differences at a glance:

Who Can Install Them?

The regulations do not specify a particular accreditation body for alarm installation, but the work involves connecting to the mains electrical supply, which falls under Part P of the Building Regulations. In practice, use a qualified electrician registered with NICEIC, NAPIT, or an equivalent competent person scheme. They can issue a Minor Electrical Installation Works Certificate for the alarm circuit, which goes into your compliance file.

If your property already needs an EICR (and it does — the five-year cycle is mandatory), ask the electrician to install the alarm system during the same visit and confirm both on the report.

What Happens at the Start of Each Tenancy

You must confirm that all smoke and CO alarms are in proper working order at the commencement of every occupation contract. That means physically testing each unit — pressing the test button and confirming the interlink triggers all units — and recording the date and result.

During occupancy, routine monthly testing is typically the contract-holder's responsibility. But replacing defective units, fixing wiring faults, and swapping expired backup batteries remains your obligation under Section 92 of the Renting Homes Act.

The Cost of Getting This Wrong

A property with non-compliant alarms is unfit for human habitation. For an unfit period, rent is not payable and rent paid in advance for that period may be recovered as a debt or offset against future rent. A Section 173 no-fault possession notice is barred while the relevant statutory requirements remain unmet. An RRO is a separate Welsh remedy for qualifying Rent Smart Wales licensing offences; an alarm breach alone does not create one.

Retrofitting a hardwired interlinked system in a typical two-storey house costs between £300 and £600 including the electrician's labour. Compared with months when rent is not payable because the property is unfit, the installation is not the expensive part.

The Fitness for Human Habitation compliance guide includes an Alarm Compliance Map that tracks the location, type, installation date, and last test date for every unit in the property — so you can prove compliance if it is ever challenged.

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