The best outdoor saunas in the UK

The Sauna Cube is a 45mm thermowood cabin that arrives with everything it needs to get hot: a 6kW Harvia Vega heater, L-shaped alder benches, a bucket, ladle and thermometer, and two headrests. Thermowood is timber heat-treated so it takes on far less moisture and moves less with the weather, which is why the walls go up without an insulated lining and still hold 80 to 100°C on a January night.

It costs £4,999.99 with a wooden front, or £5,999.99 with a full glass front. A 6kW Harvia Vega bought on its own is £366 with stones, and a design-led heater with a separate controller runs past £1,000, so the cabins that look cheaper on a listing often stop looking cheaper once a heater is added. Nothing else here seats five with the heater included for less.

Budget for two things beyond the price. The Vega needs a dedicated 32A supply, so an electrician is part of the job, and the 600kg kit is delivered flat-packed off a tail-lift and wheeled as close to the base as access allows. Polar's own carpenters will build it for a quoted fee; the warranty is 2 years with professional fitting and 1 year if you build it yourself.

The Mira is the cabin people photograph. Its whole front is tempered glass, the shell is thermally modified spruce and the interior is thermo-aspen, lit from under the benches. It comes as a kit in two sizes, the Mira S for up to two people and the Mira L for up to four, in eight colours.

Auroom belongs to the Thermory group, one of the largest producers of thermally modified timber, and the joinery shows it. The difficulty is buying one. There's no UK list price, the heater is specified per build, and dealer quotes for an imported kit land above the Sauna Cube for the same number of seats.

Four seats and an 8kW Harvia stove for £4,200. The cabin is Canadian hemlock on a 1.8m square footprint and stands 2m tall, comfortably under the 2.5m height limit for an outbuilding near a boundary.

Per heated seat, this is the cheapest serious cabin on the list. What the saving costs is wall build: hemlock panelling is thinner than 45mm thermowood, so it gives heat back to a cold night faster and uses more electricity to hold temperature. The 8kW stove also wants a 40A supply, a step above the usual 32A run.

The 6 to 8 person Cube stretches the same 45mm thermowood cabin to 2.4m deep, which buys a second run of bench and room for six to eight people. It ships with a 9kW Harvia Cilindro pillar heater, or with a 13kW Harvia M3 wood-burning stove for £1,500 more.

It's £8,499.99 with a wooden front and the electric heater, £9,999.99 with the wood stove, and £1,000 more for a glass front. The wood-fired version is the one to look at if the garden has no power: no circuit and no electrician, just a flue and dry logs. The electric version wants a dedicated 50A supply.

A 2m-long barrel that fits where a square cabin won't. The spruce kit is £4,585 without a heater, or £4,995 in thermowood, and you choose the heat: £5,495 all-in with a 6.8kW Harvia Cilindro, or £5,695 with a Harvia M3 wood stove. Barrels heat quickly for their size because there are no corners to warm.

Layzee rates it for up to four, but the curve costs shoulder room at both ends, so four is a squeeze where the Sauna Cube seats five on flat walls. For a side return, or for the ritual of feeding a fire while it rains, that's a fair trade, and delivery is included to most of the UK.

The Cove is the Sauna Cube scaled up, with a covered outdoor shower built onto the side, so the cold rinse between rounds is one step from the door. It's 45mm thermowood under an aluminium roof, with 2.18m-deep benches for four to eight people, and it ships with a 9kW Harvia Cilindro or, for £1,000 more, a 13kW wood-burning stove.

At £17,995.95 it's the most expensive cabin here, and it should be judged against garden rooms rather than sauna kits: a bespoke cabin with a plumbed shower costs more and takes months. The Cove is in stock on a 1 to 2 week delivery. Plan for a 50A supply for the 9kW heater, a water connection for the shower and a base 3.2m wide.

£3,890 buys the Eir, a compact kit cabin in 44mm spruce logs with a 6kW Narvi heater, stones and roofing felt included and free delivery to mainland UK. It stands on a 1.8m by 1.6m footprint and is 2.25m tall.

It's the cheapest complete cabin on this list, and the saving over the Sauna Cube is about £1,100. For that you get two or three seats instead of five, you do the building, and untreated spruce needs a coat of treatment every year. If the budget stops below £4,000, this is the one to get.