What is a sauna kit?
UK sellers use "sauna kit" for three quite different things, so the first job is to work out which one you are looking at.
A flat-pack or self-assembly kit is the most common. The walls, ceiling, benches, door and fixings are pre-cut and numbered, and you assemble them yourself following the instructions. Some ranges are described as straightforward; at least one seller labels a model a kit "for skilled hands". A pre-built or partially pre-assembled kit arrives built, or in a few large sections. Barrel saunas and some indoor cubes are sold this way, which is why they are the easiest route. A materials-only or build-in package is cladding, bench boards, a door, foil vapour barrier and insulation for lining a spare room, garage corner or shed, with the heater bought separately. That is really a DIY build with the shopping done for you, and the process is covered in our guide to how to build a sauna.
If you want the sauna experience with the least work, choose a pre-assembled barrel or a complete indoor kit. If you enjoy a project and have a helper, a flat-pack cabin is the best value. If you already have a room to convert, a materials package is the flexible option.
Indoor room kit, outdoor cabin kit or barrel kit?
An indoor sauna kit is a traditional electric sauna built as a room within a room: pre-cut panels or a complete cube, aspen or alder benches, a glass door and usually a matched heater. The compact two-person cubes measure roughly 1.5m by 1.3m and need about 2.2m of height, with a 2.3m ceiling the usual minimum, plus 50 to 60cm of clear space in front of an outward-opening door. They suit a garage, utility room, loft or large bathroom. If you want no electrician at all, a flat-pack infrared sauna is the one indoor kit that usually runs from a standard 13A socket.
An outdoor sauna kit is a flat-pack log or panel cabin, typically 34 to 44mm walls (thicker on premium ranges), from about 4m² of floor area up to multi-room cabins with changing rooms and porches. These need a level base, a buried power supply and, usually, a roof covering and heater bought as extras. Our outdoor sauna and garden sauna pages cover the cabins themselves, siting and planning.
A barrel sauna kit is the quickest of the three to get running: curved staves held by steel bands, benches and door included, minimal groundwork and often delivered part-built. Prices and the thermowood-versus-cedar question are covered in full on our barrel sauna page.
What is in the box, and what is not
This is where kits differ most, and where budgets go wrong. Check each item against the listing before you order.
Structure, benches and door. Included in almost every kit. Outdoor cabin kits usually include windows and 20mm floorboards too, though some bench boards and cladding may need cutting to length.
Heater and controls. Included with complete indoor kits and most barrel ranges, but often an optional extra on outdoor cabin kits, and always separate with materials-only packages. An electric heater adds roughly £300 to £1,500 depending on size and quality; a wood-burning stove £800 to £3,500 plus around £900 for a flue kit.
Roof covering. Many outdoor cabin kits ship with roof boards only, with shingles or felt as an add-on. Barrel kits more often include shingles.
Insulation and vapour barrier. Optional on log cabins, built in on insulated panel kits and indoor cubes. A foil vapour barrier roll costs around £60 and insulation boards from about £20 each if you are adding them yourself.
Base, delivery and electrics. Never included. You supply a level, drained base (paving, gravel or a slab), access for a pallet or a pre-assembled barrel, and a qualified electrician to connect the heater.
A good listing says plainly "heater included" or "heater optional". If it does not say, assume it is not in the box and ask.
Sizes, wood and heater
Kits are sold by person count, which is a seated-plus-standing maximum; comfortable use is one or two fewer. One-person indoor cabins start around 90cm square. Two-person cubes are about 1.5m by 1.3m. Outdoor cabin kits run from 2m by 2m (4m²) for two to four people up to 5m by 5m multi-room buildings. See our 2 person sauna guide if space is tight.
Thermally modified spruce (thermowood) is the standard for indoor cubes and barrels: stable, rot-resistant and low maintenance. Outdoor log cabins are mostly slow-grown pine or spruce, often with a thermowood or charred-timber upgrade. Inside, look for aspen or alder benches, which stay cooler to the touch than pine. Cedar and hemlock are premium interior options.
Heater size follows room volume: allow roughly 1kW per cubic metre, more if there is a lot of glass or the cabin is uninsulated, so a two to three person cabin of 6 to 9m³ typically takes a 6 to 8kW heater. A kit sold with a matched heater has done this sum for you, which is one of the strongest arguments for buying complete.
How hard is a sauna kit to assemble?
Plan on two people. UK retailers put flat-pack cabin assembly at two to three days for two people, or a weekend with a small team, with smaller cabins done in a day or two. Pre-assembled barrels and indoor cubes are quicker still, and a flat-pack infrared cabin is a same-day job. On top of that, allow time to prepare the base before delivery and a half-day for the electrician afterwards.
Most sellers offer an assembly service if you would rather not; expect roughly £300 to £2,160 depending on the size and complexity of the kit. The parts of a kit you should never do yourself are the fixed electrics and, for a wood-burner, the flue.
What a sauna kit costs in the UK
As a guide, complete indoor sauna kits with a heater start around £1,600 for a one-person click-together cabin with a 3.6kW heater, run about £1,800 to £3,200 for two to three person flat-pack cabins and reach about £4,100 for a Harvia package with stove and lights included; a specialist two-person thermowood cube with heater, benches and glass door is about £5,000 to £6,000; made-to-measure traditional kits run from £6,000 to £20,000. Heater-and-door equipment kits and materials-only packages for a room you line yourself start around £1,000 to £1,400, but you are buying the timber separately. Flat-pack infrared cabins top out around £3,000 for a four to five person model. Outdoor cabin kits without a heater start around £2,400 for a compact two-person log cabin and £2,800 to £4,500 for a two to four person cabin, £3,500 to £6,500 for family sizes and £5,000 to £11,000 or more with changing rooms and porches. An entry 6 to 8kW electric heater adds roughly £450 to £700 at the same checkouts. Barrel kits run from about £3,000 to £7,500, with the longest barrels reaching £11,000.
Add the heater if it is not included, the base, delivery, an assembly service if you want one, and the electrician: roughly £300 to £600 for a basic heater connection indoors and £600 to £1,200 or more for a buried outdoor run. Retailers put the saving on a kit against a custom build at 30 to 40%, which matches the ranges above but is their figure rather than ours.
Running cost is the same as any sauna of the same heater size. A 6kW heater run flat out for an hour costs about £1.58 at the current price-cap electricity rate; with the thermostat cycling, a typical 45 to 60 minute session uses roughly 3 to 5 kWh, or about 80p to £1.30. Infrared cabins at 1.5 to 2kW cost proportionately less.
Guide prices, correct as of October 2026, based on 26.32p per kWh (Ofgem cap, 1 October to 31 December 2026). The energy price cap changes quarterly, so check current rates before budgeting. Guide prices are typical UK costs, not live prices.
Electrics and planning
A traditional sauna heater is a fixed, high-load appliance in what the wiring regulations treat as a special location. Its circuit is notifiable work under Building Regulations Part P in England and Wales and must be installed by a registered electrician or notified to building control; it needs a dedicated hardwired circuit with RCD protection and an isolator outside the sauna, and armoured cable buried to an outdoor cabin. Only small infrared cabins under about 3kW run from a plug. Scotland and Northern Ireland have their own rules.
Outdoor cabin and barrel kits usually count as permitted development in England within the height and siting limits for garden outbuildings, with exceptions for listed buildings and designated land; the full walk-through is on our garden sauna page. Indoor kits need no planning permission, but check ceiling height, ventilation and floor finish before you order.