Do smoke alarms have to be interlinked or hardwired in the UK?

In England, the letting rule is a storey-by-storey alarm duty, not an interlinked or hardwired alarm duty. Scotland, Wales and Northern Ireland are different enough that “UK” answers are often wrong unless the nation is named.

Do smoke alarms have to be interlinked?

Smoke alarms do not have to be interlinked in rented homes in England, because England’s letting regulations require “a smoke alarm” on each relevant storey and do not require interlinked smoke alarms, while Scotland requires interlinked alarms in every home and Wales requires linked mains alarms. The English duty is that “a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation”, so ordinary battery alarms can satisfy the English rental rule if there is one on each required storey. Scotland’s standard says “all smoke and heat alarms to be interlinked”, and it applies to owner-occupied homes as well as rented homes. Wales goes further: the Welsh rule requires a smoke alarm on each storey that is “connected to the dwelling's electrical supply” and “linked to every other smoke alarm in the dwelling”. Northern Ireland private-tenancy rules also require smoke and heat alarms to be interlinked.

Do smoke alarms have to be hardwired or mains-powered?

Smoke alarms do not have to be hardwired or mains-powered in rented homes in England, because the English letting regulations impose no power-source requirement, but Wales requires mains-connected smoke alarms and Scotland accepts either mains alarms or sealed long-life lithium battery alarms. England’s rental duty is only that “a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation”. The confusing “mains operated” line comes from Approved Document B, which says “Smoke alarms should be mains operated and conform to BS EN 14604”; that is Building Regulations guidance for new-build and alteration work, not the letting rule for an existing rented home. Scotland expressly separates interlinking from hardwiring: “Mains-operated alarms (with battery backup) are permitted, and tamper proof long-life lithium battery alarms...are also permitted”, and alarms may be linked “via wires (hardwired) or wirelessly”. Wales alone requires both mains power and interlinking.

Do interconnected smoke alarms need to be the same brand?

No UK smoke-alarm law says interconnected smoke alarms must be the same brand, but in practice interlinked alarms usually have to be from the same manufacturer and product range to communicate with each other. The legal wording in Wales, for example, requires alarms to be “linked to every other smoke alarm in the dwelling which is connected to the electrical supply”, but it does not name a brand or manufacturer. Scotland and Northern Ireland likewise require interlinking without turning brand choice into a legal condition, and England has no interlinking duty for ordinary rented homes to attach a brand rule to. The practical limit is technical rather than statutory: Screwfix’s Wales alarm guidance warns, “Please be aware: Only products from the same brand and product range interlink with each other.” Treat a mixed-brand interconnected system as a compatibility question, not a legal-branding question.

Do interconnected smoke alarms still work if one is disconnected?

Published UK legislation and statutory guidance do not settle what happens to an interconnected smoke-alarm system if one unit is disconnected, because disconnection behaviour is a product-design issue rather than a legal rule. The law sets duties such as having alarms and, in Scotland, Wales and Northern Ireland, having them interlinked; it does not specify whether the remaining alarms keep detecting independently, whether the link fails, or whether the system reports a fault when one head is removed. Approved Document P, for example, addresses whether electrical work is notifiable and says “All other electrical installation work is not notifiable”, but it does not describe alarm fault behaviour. The safe answer is to check the manufacturer’s instructions for the exact model and range, because radio-linked, hardwired-interlinked and hybrid systems can be designed differently. Do not assume that “interconnected” means every remaining unit behaves the same after one is disconnected.

Do you need an electrician to replace a hardwired smoke alarm?

In England, you do not legally need a registered electrician or a building-control notification for a like-for-like replacement of a hardwired smoke alarm, unless the work includes a new circuit, consumer-unit replacement or work in a special location. Approved Document P says, “Regulation 12(6A) sets out electrical installation work that is notifiable. All other electrical installation work is not notifiable.” The notifiable categories are where “the work consists of— (a) the installation of a new circuit; (b) the replacement of a consumer unit; or (c) any addition or alteration to existing circuits in a special location.” A straightforward swap of an existing mains smoke alarm on the existing wiring is normally repair or maintenance, not one of those categories. That does not make it a DIY recommendation: if the alarm is mains-powered, the circuit must be safely isolated and the replacement must be compatible with the base, wiring and interlink system.

Can you sell a house without interlinked smoke alarms?

In England, you can sell an owner-occupied house without interlinked smoke alarms because England has no general owner-occupier smoke-alarm duty and its alarm regulations bind relevant landlords, not private sellers. The English rental rule says “a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation”, but that is a letting duty, not a conveyancing gate for an owner-occupied sale. Scotland is different: every home must meet the tolerable standard, which includes having “satisfactory equipment installed for detecting, and for giving warning of, fire or suspected fire”, and Scottish Government guidance says, “It is the property owner's responsibility for meeting the standard.” Even in Scotland, the duty is continuous rather than triggered by sale; the rule is not a special Home Report or registration condition. Wales’ cited alarm rule is a Renting Homes fitness rule, and Northern Ireland’s cited rule is for private tenancies, so neither source establishes an interlinked-alarm condition for selling an owner-occupied house.

Do you need interlinked or hardwired alarms before you can take in a lodger?

In England, a resident landlord taking in a lodger does not need interlinked or hardwired smoke alarms under the Smoke and Carbon Monoxide Alarm Regulations, because a tenancy where the occupier shares accommodation with the landlord is excluded. The English exclusion covers “A tenancy under the terms of which the occupier shares any accommodation with the landlord or a member of the landlord's family.” Even where the English regulations do apply, the duty is only that “a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation”, with no interlinking or hardwiring requirement. Wales has a similar exclusion where the tenancy or licence provides for the occupier “to share any accommodation with the landlord”. Scotland is the exception: “Every home in Scotland must have interlinked fire alarms”, so the property standard applies before and after taking in a lodger.

Do you have to have a smoke alarm in the hallway?

In England, the statute does not require a smoke alarm specifically in the hallway; it requires one smoke alarm on each storey that contains living accommodation. The English wording is that “a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation”, so the legal test is storey coverage, not the word “hallway”. Scotland is stricter and more specific: Scottish Government guidance says the standard includes “one smoke alarm in every hallway and landing”. Wales requires a smoke alarm on each storey of the dwelling that is mains-connected and linked to the other mains smoke alarms, while Northern Ireland private-tenancy guidance requires interlinked smoke and heat alarms but is not the same as England’s storey-only wording. In practice, hallways and landings are common alarm positions because they form escape routes, but England’s rental regulation itself does not name them.

Last reviewed August 2026.

Sources

• “Smoke and Carbon Monoxide Alarm (England) Regulations 2015 reg.4: — "a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation” Source
• “Smoke and Carbon Monoxide Alarm (England) Regulations 2015 reg.4, as amended 1 October 2022: — "a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation” Source
• “Approved Document B Volume 1, Dwellings: — "Smoke alarms should be mains operated and conform to BS EN 14604.” Source
• “Renting Homes (Fitness for Human Habitation) (Wales) Regulations 2022 reg.5: — "on each storey of the dwelling there is a smoke alarm which is...(b)connected to the dwelling's electrical supply, and (c)linked to every other smoke alarm in the dwelling which is connected to the electrical supply” Source
• “Renting Homes (Fitness for Human Habitation) (Wales) Regulations 2022 reg.5: — "linked to every other smoke alarm in the dwelling which is connected to the electrical supply” Source
• “Scottish Government tolerable standard guidance: — "all smoke and heat alarms to be interlinked” Source
• “Scottish Government tolerable standard guidance: — "Mains-operated alarms (with battery backup) are permitted, and tamper proof long-life lithium battery alarms...are also permitted” Source
• “Scottish Government tolerable standard guidance: — "Alarms can be interlinked via wires (hardwired) or wirelessly (by radio communication).” Source
• “Northern Ireland Department for Communities guidance, Smoke, Heat and Carbon Monoxide Alarms for Private Tenancies Regulations (Northern Ireland) 2024: — "Smoke and Heat alarms (mains wired, battery, or a combination of both) must be installed on the ceiling and be interlinked.” Source
• “Screwfix Wales fire alarm guidance: — "Please be aware: Only products from the same brand and product range interlink with each other.” Source
• “Approved Document P, 2013 edition: — "Regulation 12(6A) sets out electrical installation work that is notifiable. All other electrical installation work is not notifiable” Source
• “Approved Document P, 2013 edition: — "the work consists of— (a) the installation of a new circuit; (b) the replacement of a consumer unit; or (c) any addition or alteration to existing circuits in a special location.” Source
• “Housing (Scotland) Act 1987 s.86: — "has satisfactory equipment installed for detecting, and for giving warning of, fire or suspected fire” Source
• “Scottish Government fire and smoke alarms factsheet: — "It is the property owner's responsibility for meeting the standard.” Source
• “Scottish Government fire and smoke alarms factsheet: — "Every home in Scotland must have interlinked fire alarms.” Source
• “Scottish Government fire and smoke alarms factsheet: — "one smoke alarm in every hallway and landing” Source
• “Smoke and Carbon Monoxide Alarm (England) Regulations 2015 Schedule: — "A tenancy under the terms of which the occupier shares any accommodation with the landlord or a member of the landlord's family.” Source
• “Renting Homes (Wales) Act 2016 Schedule 2: — "the terms of the tenancy or licence provide for the tenant or licensee to share any accommodation with the landlord” Source