How to choose a home sauna

Sauna shopping goes wrong when people start with brands. The market has hundreds of them and they blur together fast. Start instead with six decisions in a fixed order, because each one eliminates most of the market, and by the fourth you are choosing between three or four real products rather than a hundred listings.

1. Traditional or infrared

This is the decision everything else hangs off. Traditional cabins heat air to 80°C to 100°C and let you throw water on stones. Infrared cabins heat your body directly at 30°C to 65°C, plug into a normal socket, and cost about a quarter as much per session.

Neither is a substitute for the other, and the full comparison of infrared against traditional heat covers the mechanism. For shortlisting purposes: pick traditional if you want the ritual and the heat, infrared if you want to use it four times a week without thinking about the bill. If what you actually picture is warm wet air rather than dry heat, that is a third option again, and dry heat against a steam room is the comparison that settles it.

2. Indoors or outdoors

Outdoors buys capacity. A garden cabin can be three or four times the volume of anything you will fit in a spare room, so families and anyone who wants to lie down rather than sit up ends up outside. It also costs more to run, because a cabin in a British winter loses heat that an indoor one does not, and it has to fit inside the height limits the Planning Portal sets for outbuildings.

Indoors buys convenience and lower running costs. It also avoids the base, the trench and the weather, which is most of the project management. The practical constraint is ceiling height, since most indoor cabins need about 2.1m. Going outdoors also opens a fuel choice that indoors effectively forecloses, and burning wood against running a circuit is decided by your address as much as your taste.

3. How many people, honestly

Capacity claims across this industry are optimistic, and the fix is to count how people will actually sit. A cabin sold as two person seats two adults upright, shoulder to shoulder, with no room to lie down. Lying down needs a bench of about 1.8m, which in practice means a cabin sold as three to five person.

Buy for the way you will use it most, not the once-a-year maximum. A two person cabin used nightly beats a six person cabin used monthly because it is cheaper to heat and quicker to get into. The arithmetic behind that, 60cm of bench per seated adult and 1.8m to lie down, is worked through in how many people a sauna actually seats.

4. Whether the heater is included

This is the single most common pricing trap in the category. Most indoor cabins and self-build kits are sold as shells, with the heater bought separately for £600 to £900, because output has to be matched to cabin volume. A few complete outdoor cabins include one, which is worth real money at comparison time.

It is exactly why the shells that top our indoor sauna rankings list at £3,577.45 while a complete outdoor cabin with a 6kW Harvia in the box lists at £4,999.99. Those two numbers are closer than they look once the heater and its installation are added to the first one, and the output you need is set by cabin volume rather than by budget, which is what matching a heater to the room is for.

• Ask whether the price includes the heater, the stones, the control panel and the door
• Ask what heater output the maker specifies for that cabin volume
• Ask whether delivery is kerbside or into the garden, since a 600kg flatpack is not a two-person carry
• Ask what the warranty requires you to do, because annual wood treatment is a common condition

5. Materials, and which claims are worth paying for

Timber choice is where marketing gets thickest, so here is the short version of what the common options actually do.

Two rules cover most of it. Anything your skin touches should be a low-conductivity timber like aspen or alder, because metal fixings and dense wood at 90°C burn. Anything outdoors should be thermally modified or treated, because untreated softwood in British weather is a maintenance commitment you will resent.

6. The budget nobody quotes

The list price is the start of the number. These are the additions that turn a £4,999 cabin into a £7,000 project, and every one of them is predictable:

The electrical line is the one that is genuinely non-negotiable on a traditional build, since a new circuit is notifiable under Approved Document P, which is why a sauna circuit has to be installed and certified by a registered electrician rather than added to an existing one. On the running side, a session costs about £1.57 traditional or 42p infrared at Ofgem's current cap rate, and the figures behind what a sauna costs per session are what decide whether the thing gets used.

Three shortlists to start from

Once the six decisions are made, the shortlist is small. For a garden cabin for a household of three to five, start with the complete outdoor cabins where the heater is in the box. For a spare room, start with the indoor shells and price the heater alongside. For a flat, or for nightly use on a budget, start with plug-in infrared.

If the budget is open and the sauna is meant to be an architectural piece rather than a product, that is a different market again, and the commissions and engineered systems in our luxury sauna rankings are where it starts.