The outdoor sauna buying guide: 6 decisions that matter

Most sauna regret is not about the maker. It is a cabin bought one size too small, a stove that turned out to be extra, a base poured after the delivery truck left, or 90°C heat bought by someone who wanted 40 minutes of warmth. Six decisions, made in order, prevent all of it, and the order matters because each one narrows the next.

Decision 1: which heat you are actually buying

A traditional sauna heats air to 80–100°C with an electric stove or a wood fire, and throwing water on the stones flashes it into löyly, the steam hit the whole ritual is named for. Sessions run in 10 to 20 minute rounds with cool-downs between. An infrared cabin runs 30–65°C panels that warm you rather than the room, in 30 to 45 minute continuous sessions that cost pennies.

Neither reproduces the other, and the two heats differ in cost, installation and feel far more than any two brands differ within one camp. Decide this first: everything downstream, from wiring to footprint, follows the heat. Buyers torn between them usually resolve it with one question, whether the water-on-stones moment matters. If yes, traditional; if the answer is a shrug, infrared will get used more.

Decision 2: where it stands

In England a garden building within 2m of a boundary is fine under permitted development up to 2.5m of height, which is why nearly every purpose-built cabin stands about 2.1m tall. Further into the garden the ceiling lifts to 3m. Conservation areas, listed buildings and flats sit outside these rights, and Scotland, Wales and Northern Ireland run their own versions, so a council check costs five minutes and a retrospective application costs considerably more.

The base is the site decision people actually get wrong. A 3–5 person cabin weighs about 600kg empty, so it needs a level, load-bearing surface: a concrete slab, paving on a compacted sub-base, or a reinforced deck, at £400 to £1,500 depending on ground and labour. It must be laid and cured before delivery day, because a made-to-order cabin arriving with nowhere to stand becomes an expensive storage problem. Plan the cable run or flue route at the same time, since trenching armoured cable across a finished lawn twice is nobody's favourite weekend.

Decision 3: seats, counted honestly

Allow about 60cm of bench per seated adult, and 1.8m of straight bench for anyone lying down. That second number is the one that resizes purchases: a two-person cabin seats a couple upright and nothing more, and the stretch-out that people picture needs a 3–5 person interior. The couple-sized cabins start at 1200mm square footprints, and the step from a two-seater to the leading family cabins can be as little as £500, which buys the lying-down bench and the spare seats in one move.

Buy for the sessions you will actually hold, then round up once if the garden allows it. The used market for garden saunas is thin, so trading up later costs far more than sizing up now.

Decision 4: shape and timber

Shape first: a cabin gives the most bench per metre and takes an L-shaped layout; the barrel form heats faster for its volume, sheds rain by geometry, carries the wood-fired option at published prices, and pays for all of it in shoulder room at the curved ends.

Then timber, which sets both the winter bill and the maintenance calendar. 45mm thermowood is the insulation benchmark, holding temperature with the stove cycling gently. Cedar resists rot on its own oils and weathers to silver with no treatment cycle. Softwood panels and spruce staves are the budget route and want a breathable coat every year or two, at £40 to £80 a time, often as a warranty condition rather than a suggestion.

Decision 5: the stove and its wiring

Size the heater at roughly 1kW per cubic metre of cabin and round up for glass and winter, which lands the common 2m garden cabin at 6kW and family sizes at 8kW. The choice of stove then splits three ways: electric with controls on the unit, electric with a separate controller and app, or a wood burner with no wiring at all.

Electric means a dedicated circuit, 32A for the 6kW class and 40A at 8kW, run from the consumer unit as notifiable work under Part P and certified by a registered electrician at £300 to £800. Keep the certificate: insurers and solicitors ask for it. Wood fire swaps the circuit for a flue kit, clearances, a £15 carbon monoxide alarm and £4 to £7 of logs a session, and adds 15 to 20 minutes of tending to every heat-up.

Decision 6: the delivered price, not the sticker

The advertised number and the cost of a working sauna are different figures, and the gap is predictable. A missing heater adds £600 to £900. The circuit adds £300 to £800. The base adds £400 to £1,500. Professional assembly, worth having for a 600kg flatpack delivered kerbside on a tail-lift, adds £1,200 to £2,000, and on most makes self-assembly halves or voids parts of the warranty.

This is why complete cabins with the stove included dominate the main outdoor sauna ranking: a published price with the heater inside it is the only number that can be compared without a calculator. Where a maker quotes per project, fix the delivered scope in writing, cabin, stove, controls, stones, delivery and any crane, before comparing anything.

The health question, briefly

Heat bathing carries a genuinely encouraging research record, led by Finnish cohort data associating frequent sauna use with lower cardiovascular mortality, and the evidence for heat bathing is worth reading in full before repeating any specific claim. The honest summary for a buyer: the literature is a reason to be unworried about the habit, not a reason to spend £5,000. Buy the heat you will sit in three times a week, because frequency is the one variable every study agrees on.