Electrics, Part P and notifiable work
Any electrical work in your home, garden, garage or outbuilding has to comply with the Building Regulations, and all of it should follow BS 7671, the IET Wiring Regulations. Part P is the part that covers dwellings in England and Wales; the two nations now use different editions of the guidance, and Wales notifies more work. Some of that work is "notifiable", which means building control has to know about it and it has to be certificated when it is finished.
Three kinds of work are notifiable: replacing a consumer unit, installing a new circuit, and any addition or alteration to an existing circuit in a "special location". In England, regulation 12 of the Building Regulations defines a special location as the zone around a bath or shower and any room containing a swimming pool or a sauna heater (Approved Document P, 2013 edition, paragraph 2.5). Wales still uses the 2006 edition of Approved Document P, which lists hot air saunas, bathrooms and swimming pools as special locations and treats kitchens and outdoor lighting or power as areas where any extension to a circuit is also notifiable. A traditional heater of 6 kW typically needs its own 32 A circuit and a 9 kW heater about 40 A, hard-wired through an all-pole isolator with heat-resistant cable. A hard-wired heater is therefore a new circuit, and notifiable, whichever nation you live in.
The simplest route is an electrician registered with a government-authorised competent person scheme, such as NICEIC (Certsure) or NAPIT. They self-certify the work and notify building control for you. If your electrician is not registered, the work has to be notified to building control before it starts and inspected afterwards, or the installer can appoint a registered third-party certifier before work begins. Either way you should finish with two documents: an Electrical Installation Certificate and a Building Regulations compliance certificate. Keep both; you may be asked for them when you sell.
Plug-in equipment is different. An infrared cabin or an ice bath chiller that plugs into an existing, suitable socket is not notifiable work. What matters is that the socket is right: earthed, protected by a 30 mA RCD and, outdoors, an IP-rated weatherproof socket. Never run a chiller from an extension lead or adaptor. If the nearest socket is in the wrong place, adding one is a small electrician job, and a new outdoor circuit is notifiable in both nations. In Wales any new outdoor wiring, even an extra socket on an existing circuit, is notifiable too.
Planning permission and building regulations for a garden cabin
In England a garden sauna is treated as an outbuilding and usually falls under permitted development, so no planning application is needed as long as it is single storey, with eaves no higher than 2.5 m and an overall height of no more than 4 m for a dual-pitched roof or 3 m for any other roof; no more than 2.5 m tall if it sits within 2 m of a boundary; not forward of the principal elevation of the house; and, together with any other outbuildings, covering no more than half the land around the original house. On designated land such as national parks, the Broads, Areas of Outstanding Natural Beauty and World Heritage Sites, anything more than 20 m from the house is limited to 10 m², and within the curtilage of a listed building any outbuilding needs permission. That guidance covers England; Wales is similar but check gov.wales before you order. Scotland and Northern Ireland use different limits, summarised below.
Building Regulations for the cabin itself are a separate question from Part P. In England and Wales a detached single-storey garden building under 15 m² with no sleeping accommodation normally falls outside them, and one of 15 to 30 m² does too if it is at least 1 m from any boundary or built mainly of non-combustible materials. The exemption does not extend to the electrics: Approved Document P states that sheds and garages which share the house's electricity supply are not exempt from Part P. For the detail on space, bases and the boundary rules, the garden sauna page goes deeper.
A wood-burning stove brings two more rules. The stove and flue fall under Approved Document J, which covers combustion appliances, so fitting one is controlled work normally done or signed off by a HETAS-registered installer, with a carbon monoxide alarm fitted. And if you live in a smoke control area you can only burn wood in a Defra-exempt appliance; your council's environmental services team can tell you whether you are in one.
Scotland and Northern Ireland
In Scotland, Part P does not apply. Electrical work is covered by the Scottish building standards instead (Standard 4.5) and must meet BS 7671 whether or not a building warrant is needed. Most electrical work inside a house, and a detached electric garden sauna of up to 30 m², need no warrant, but a wood-fired stove with a flue or any sanitary fitting takes the building out of that list, and starting warrantable work without a warrant is an offence. Where a warrant is needed, an approved certifier of construction registered with SELECT or NICEIC can certify the electrics. For planning, a garden building behind the house is permitted development if it is no higher than 4 m, with eaves no higher than 3 m, no higher than 2.5 m within 1 m of a boundary, and does not take up half or more of the rear garden; conservation areas (8 m² footprint) and listed buildings (4 m²) are tighter.
In Northern Ireland the Building Regulations contain no electrical part and there is no statutory equivalent of Part P for owner-occupied homes, so there is nothing to notify. Electrical Safety First still recommends a registered electrician working to BS 7671 who issues an Electrical Installation Certificate. A detached single-storey building of up to 30 m² with no sleeping accommodation is exempt from building control if it is non-combustible or at least 1 m from the house, a road and the boundary. For planning, a garden building of up to 4 m high, with eaves no higher than 2.5 m within 2 m of a boundary, not forward of a wall facing a road and not covering more than half the plot, is permitted development; listed buildings and designated areas are restricted.
What installation costs
Cabin and tub prices are on the product pages. These are the installation elements, as guide prices for a typical two to four person garden sauna. A concrete or paved base runs around £60 to £75 per m² installed, so roughly £300 to £1,000 for a typical cabin, more for a large or awkward site. Power is the variable: £300 to £600 for a short, simple connection where a suitable supply is already close, and £800 to £2,500 for a new buried armoured-cable run and dedicated circuit, with a long run, a consumer unit upgrade (£400 to £700 or more) or a patio or driveway crossing pushing it higher. Electricians charge roughly £300 to £400 a day, more in London. One UK retailer prices professional assembly of its prefabricated saunas at about £1,250 to £1,600 for a two to three person cabin, £1,800 to £2,200 for four to five and £2,200 to £2,890 for six to eight. Delivery is typically £150 to £400, often free to the UK mainland with surcharges for the Highlands and islands.
Guide prices, correct as of October 2026, drawn from published UK trade and supplier cost guides. They are typical costs, not quotes. Access, ground conditions and region move them, so get two or three itemised quotes.
How long it takes
Allow for the sequence rather than a single day. Planning checks and quotes come first. A base takes two to three days including curing and must be finished before the cabin arrives. The electrician normally does a first fix (trench, cable and isolator) before delivery and connects the heater afterwards. Cabins typically ship in two to four weeks from stock, though bespoke builds take far longer. Assembly of a typical two person outdoor cabin takes eight to twelve hours for two or three people, or one to two days; an infrared cabin takes a few hours; a barrel sauna sits between the two. Ask every supplier for their current lead time rather than relying on a figure from a web page.
Ice bath and cold plunge installation
Most home ice baths are not installed in the building sense. A portable or inflatable tub fills from a hose, and a cold plunge tub with an ice bath chiller is plug-in; consumer chillers draw well under the capacity of a 13 A socket. The installation is really three things. A hard, flat, drained surface that can take the weight: one leading UK brand requires a surface rated to 610 kg for its barrel and chiller, and decking or an upstairs floor may not qualify. A compliant socket: earthed, 30 mA RCD-protected, IP-rated outdoors, with no extension leads or adaptors. And room to work: a hose within reach, about 30 cm of ventilation clearance around the chiller and access to remove its side panel for maintenance. Permanently plumbed plunge pools are a bespoke build and a different conversation.
If you are planning a sauna and a plunge together, site them on one base and have the electrician size the supply for both in one visit. It is cheaper than two trenches and two call-outs, and it is how most garden recovery set-ups end up.
DIY or professional?
Flat-pack assembly is realistic for a capable person with a helper and a weekend, and so is a simple paved base. The suppliers design the kits for it, though one retailer's advice on foundations is blunt: unless you are experienced, do not build the base yourself. How to build a sauna covers the self-build route. Fixed electrical work and stove or flue work are the lines not to cross. They are notifiable or controlled, they have to be certificated, and uncertificated work may cause problems with insurance or when you sell. Pay a registered trade for those two and do the rest yourself if you like.
