Sauna vs steam room: what's the difference, and which works in a UK home?

A sauna is dry heat — 70–100°C at 5–15% relative humidity, produced by an electric or wood-fired stone heater inside a timber cabin. A steam room is wet heat — 40–48°C at close to 100% humidity, produced by a steam generator feeding a sealed, tiled enclosure. The sauna is far hotter by thermometer; the steam room usually feels more intense, because saturated air stops sweat evaporating and takes away your main cooling mechanism.

For a UK home the decisive difference isn’t the heat at all. A sauna is a cabin you can put in a garden on a base with a power supply. A steam room is a wet-room construction project. That is why this site’s whole lead flow is saunas and cold plunges: a home steam room belongs to a bathroom fitter, not a sauna supplier.

The numbers

	Sauna	Steam room
Air temperature	70–100°C (infrared cabins 45–60°C)	40–48°C
Relative humidity	5–15%, spiking after löyly	~100%, saturated
Heat source	Electric or wood-fired stone heater	Plumbed electric steam generator
Typical session	8–15 min rounds, with cool-downs	10–20 min
Interior	Timber — aspen, alder, thermowood	Tile, stone, acrylic or glass
Can it go outdoors?	Yes, routinely	No, in practice
Warm-up	30–45 min (15–25 min infrared)	10–20 min
Plumbing needed	None	Water supply and drainage
Home install cost	£3,000–£15,000	£5,000–£15,000+

What each actually feels like

In a sauna, the air is hot and dry enough that your sweat evaporates freely, which is why you can tolerate 90°C at all. The heat is on your skin and in your breath. Throwing water on the stones — löyly — produces a short humidity spike that makes the same temperature feel dramatically hotter, then fades. Benches are tiered because it’s meaningfully cooler near the floor, so you can choose your intensity. Most people go in rounds: 10 minutes, cool down, back in.

In a steam room, you’re in visible fog. The air is only slightly above body temperature but you cannot shed heat, so it builds. Surfaces are wet and everything you touch is warm and slick. Breathing feels different — many people find humid air easier on the nose and throat than dry sauna air, which is the most-cited subjective advantage. Sessions tend to be one sitting rather than rounds, and 15 minutes is plenty.

The construction difference, which is the whole story at home

A home sauna

A timber cabin, insulated and vapour-sealed on the inside face, with a heater and a bench. It doesn’t need water. It doesn’t need drainage. It doesn’t need to be watertight in the plumbing sense — the vapour barrier is protecting the structure from occasional humidity, not from standing water.

Outdoors, that means a level base, an electrical supply and a delivery. See garden sauna for the full sequence. Indoors, a prefabricated cabin drops into a spare room, and an infrared sauna typically just plugs into a 13A socket. The only notifiable work is usually the electrics, under Part P of the Building Regulations.

A home steam room

Everything a wet room needs, plus a sealed vapour envelope:

• Full tanking. A continuous waterproof membrane behind every tile, floor and walls, carried up to and across the ceiling. Saturated air finds every unsealed joint, and the failure mode is rotted timber or damaged plaster in the room next door, usually discovered late.
• A ceiling laid to fall. Steam condenses on the ceiling and drips. A correctly built enclosure slopes the ceiling so condensate runs to the walls rather than onto your head.
• Drainage and a gradient to it. Condensate and washdown water have to go somewhere.
• A sealed door, full height, with a proper compression seal — not a shower door.
• Mechanical extraction, on an overrun timer, to dry the enclosure after each session.
• A steam generator, typically 4.5–9 kW for a domestic enclosure, sited in a ventilated cupboard within a few metres, plumbed to a mains water feed and wired to its own circuit. In hard-water parts of the UK — most of the South and East — scale is the main killer of generators, so factor in softening or a generator with an auto-flush cycle.
• Bathroom electrical zones. Everything inside is a special location under the wiring regulations, so fittings, IP ratings and RCD protection all matter.

None of this is exotic; bathroom fitters do it every week. But it is a room being rebuilt, with tiling and plumbing on the critical path, and it can’t be undone easily if you change your mind.

Cost to install and run

Install. A steam generator is £700–£2,500. A complete home steam enclosure — tanked, tiled, sealed, drained, ventilated, controlled — realistically runs £5,000–£15,000, and past that with natural stone or bespoke glazing. Prefabricated steam pods and steam-shower cubicles are cheaper at £2,000–£6,000 and are a legitimate compromise, though they’re closer to a shower with a steam function than a steam room.

A sauna spans a similar headline range but the money sits in the cabin rather than in trades: £900–£6,000 for infrared, £3,000–£8,000 for an indoor traditional cabin, £6,000–£12,000 all-in for a decent garden sauna. Home sauna cost breaks it down, and our sauna cost calculator prices a specific build.

Running. At around 26p per kWh — roughly the Ofgem capped rate for July–September 2026 — a 6 kW generator heating for 15 minutes and cycling through a 25-minute session uses on the order of 3–4 kWh, or 80p–£1.05 a session, plus a few litres of water. A 6 kW traditional sauna is £1.50–£2.50 a session because of the longer warm-up; an infrared cabin is 30–40p. So steam sits in the middle. See sauna running costs for the assumptions.

Maintenance and the mould question

A sauna dries itself. Leave the door ajar and the vents open and the timber is dry within the hour. Annual jobs are sanding benches, replacing crumbled heater stones and checking seals.

A steam room does not dry itself. Every surface is repeatedly saturated, so the defences are structural: continuous tanking, large-format tiles with minimal grout, a falling ceiling, and extraction that runs on after each use. Add periodic descaling of the generator, which in hard water areas is the difference between a ten-year appliance and a four-year one. A steam room that gets shut up wet after every session will grow mould in the grout, and that is a maintenance failure rather than a design flaw.

Which is realistic for a UK home?

For most people, the sauna — not because it’s better, but because it’s a purchase rather than a project, it can go in the garden where you have space rather than in the bathroom where you don’t, and it can be reversed by selling the cabin.

A home steam room makes sense when you’re already refitting a bathroom or building an extension, have the ceiling height and the drainage, and specifically prefer humid heat — for example if dry sauna air bothers your airways. In that case, spec it into the build rather than retrofitting it later.

If contrast is what you’re after — heat then cold — a sauna paired with a cold plunge is the far easier arrangement to achieve at home, and the one this site is built around. Our sauna selector will point you at a format in about a minute, and are home saunas worth it does the cost-benefit without flattering the purchase.

Health note

Both are heat exposure and both carry the same cautions. Talk to your GP before using either if you have a heart condition, uncontrolled blood pressure, a history of arrhythmia or fainting, or if you are pregnant. Don’t use either after drinking alcohol, hydrate, and leave when you stop feeling comfortable rather than finishing the clock. Claims that either one detoxifies the body, cures respiratory conditions or produces lasting weight loss are not supported by good evidence — the weight you lose in a session is water, and it comes back.