Garden sauna: the complete UK guide to buying and installing an outdoor sauna

A garden sauna is a free-standing timber cabin with its own heater, sitting on its own base and fed by its own outdoor electrical supply. In the UK it is normally three separate purchases that people budget as one: the cabin, the groundworks, and the electrics. Most fall under permitted development, so planning permission is rarely needed — but a base, a Part P-notifiable supply and honest access for delivery are all non-negotiable.

Realistic all-in budget for a good four-person outdoor sauna in 2026: £6,000–£12,000. Premium cabins and pods go well past that.

Barrel, cabin or pod?

The shape decision drives cost, heat-up time and how much of it you can actually sit in.

Barrel saunas are the entry point and still the most common thing sold. Curved staves shed rain well, the reduced internal volume heats fast, and they look distinctive. The trade-off is usable space: the curve eats headroom at the benches and the floor is narrow, so a “four-person” barrel seats four people sitting still. There’s no cavity to insulate, so heat retention depends entirely on stave thickness — look for 42mm minimum, 60mm+ for winter comfort. The steel tensioning bands need re-tightening annually as timber moves.

Cube and cabin saunas are framed, insulated and clad like a small building. Full headroom, proper two-tier benching, room for a changing porch, and far better heat retention through a British January. They cost more and need a flatter, better-prepared base. If the sauna is going to be used from November to March — which in the UK is when you want it — this is the sensible shape.

Pods are the design-led end: teardrop, ovoid or panoramic-glass cabins, often factory-built and craned in complete. Excellent build quality, generally excellent insulation, and a price to match. Delivery constraints are their real limitation.

There’s a fuller side-by-side on barrel vs cabin sauna.

Timber, and how it behaves in UK rain

Two different jobs here: the outside has to survive persistent damp, and the inside has to be safe to sit on at 90°C.

For external cladding, thermowood is the default recommendation. It’s spruce or pine thermally modified at around 200°C, which drives out moisture and breaks down the sugars that feed rot. It’s dimensionally stable, doesn’t need chemical preservative, and silvers to grey over two or three years — you can leave it or oil it annually to hold the colour. Western red cedar is naturally durable, stable and lovely, but expect a meaningful premium. Untreated Nordic spruce is the cheap option and the one that gets replaced first; if a quote looks implausibly low, this is usually why.

Inside, the rule is no resin and low thermal conductivity. Aspen, alder and thermo-aspen are the standard bench timbers — they stay touchable at temperature and won’t weep resin onto skin. Pine benches are a false economy and occasionally a burn.

Heaters: electric or wood-fired

Electric is the default for a UK garden. Sizing runs at roughly 1 kW per cubic metre of well-insulated cabin, so a typical four-person outdoor sauna wants 6–9 kW. A 6 kW heater draws around 26A and a 9 kW around 39A, which means a dedicated wired circuit, correctly sized cable and RCD protection — nothing here plugs in. Add an external controller if you want to preheat from the house.

Wood-fired is the better experience for a lot of people: fiercer heat, no electricity bill, and the fire is part of the ritual. It brings obligations:

• A twin-wall insulated flue through the roof, terminating clear of the roofline, installed to the manufacturer’s stated clearances to combustibles — typically 50–100mm — with a heat shield and a non-combustible hearth.
• Smoke control areas. Large parts of urban Britain are designated. In one, you may only burn wood in a Defra-exempt appliance, and emitting smoke from a chimney can attract a penalty of up to £300. Your local council confirms whether you’re in one — the rules are set out at gov.uk/smoke-control-area-rules.
• Neighbours and insurance. Woodsmoke drifts. Tell your home insurer you’ve installed a solid-fuel appliance; some policies want it noted.
• Fuel and time. Dry seasoned wood, storage for it, and 45–90 minutes of tending to get to temperature.

Many outdoor saunas are ordered electric and retrofitted for wood later, or the reverse. Decide early, because the flue penetration and hearth are structural.

Base and groundworks

This is the part people underbudget. A filled four-person cabin with occupants is 1,000–2,000 kg on a small footprint, and it must be dead level or the door won’t seat and the glass will stress.

Three workable options:

1. Paving slabs on a compacted MOT Type 1 sub-base. Cheapest competent solution, good for barrels on cradles. £600–£1,200 for a typical footprint.
2. A reinforced concrete pad, typically 100mm on hardcore. The permanent answer for a heavy cabin or pod. £1,200–£2,500.
3. Ground screws or helical piles. Fast, minimal spoil, forgiving on sloping or soft ground, and increasingly the choice for garden buildings. Comparable cost to concrete but installed in a day.

Leave the timber off the ground — bearers, screws or a slab lip — and make sure water can run away from the base rather than sitting under it. And put a drain or soakaway somewhere useful if you’re pairing the sauna with a cold plunge.

Where to put it

Practical, in priority order:

• Close to the house. The single strongest predictor of whether a garden sauna gets used in February is how far you have to walk in a dressing gown. Twenty metres down a dark lawn is a sauna you use in July.
• Out of the prevailing wind, which in most of the UK is south-westerly. A cabin door facing into driven rain is a cabin with a wet changing bench.
• Privacy, in both directions. Glass fronts are lovely and also very visible from a neighbour’s upstairs window.
• Clearance for the flue if wood-fired, and clear of overhanging trees generally.
• Boundaries. Within 2m of a boundary, permitted development caps overall height at 2.5m, which rules out some pitched-roof cabins.

More detail on where to put a garden sauna, and the planning rules in full on garden sauna planning permission.

Electrical supply

Even a wood-fired sauna wants light and probably a socket. An electric one needs a real circuit.

Running a supply to a garden building is notifiable work under Part P and should be done by a registered electrician: SWA cable buried at the correct depth or clipped on an appropriate route, a small consumer unit in the outbuilding, RCD protection, and the heater on a correctly sized radial with the controller wired per the manufacturer’s instructions. Budget £500–£1,500 depending on cable run and whether the existing consumer unit has capacity. Expect an installation certificate at the end.

Insulation, vapour control and ventilation

For a framed cabin: 50–100mm mineral wool between studs and in the roof, then a foil vapour barrier on the warm side with all seams taped, then a batten cavity, then the internal cladding. The foil is not optional — it stops moist air reaching the cold structure and rotting it from the inside.

Ventilation is routinely skipped and shouldn’t be: a low inlet near the heater and an adjustable high outlet on the opposite wall. Without it the cabin stratifies, feels stale and dries out slowly after use.

Delivery and access

Ask before you order. Barrels arrive either assembled on a lorry or as staves on a pallet; cabins arrive flat-packed; pods often arrive complete and need craning. You need side access of roughly a metre for flat-pack, considerably more for anything pre-assembled, and a HIAB or crane lift over a house runs £400–£1,200. Self-assembly of a barrel is a realistic weekend for two competent people; a framed cabin usually isn’t. Professional assembly runs £800–£3,000 — covered on sauna installation.

Maintenance

Annually: re-tension barrel bands, re-oil or leave the cladding, check and reseal door glass, sweep the flue if wood-fired, and inspect the base for movement. Every year or two: replace the heater stones, which crumble and restrict airflow. After each use: leave the door ajar and vents open so the cabin dries. Sand the benches when they go rough.

What it all costs

Item	Indicative UK cost, 2026
Barrel sauna, 4-person	£4,000–£8,000
Framed cube/cabin, 4-person	£6,000–£15,000
Premium pod / panoramic	£15,000–£30,000+
Base and groundworks	£600–£2,500
Electrical supply and heater circuit	£500–£1,500
Wood-fired flue kit and hearth	£400–£1,200
Delivery and crane	£200–£1,500
Professional assembly	£800–£3,000

These are indicative ranges, not quotes. Our sauna cost calculator puts a figure on your specific build, and home sauna cost breaks down where the money goes. If you’re still choosing between outdoor heat and an indoor cabin, start with infrared sauna — it’s a very different proposition for a fraction of the groundworks.