Steam & Oak Kaari 300 Sauna Pod — 6 Person Thermowood with Covered Terrace

The Kaari 300 is the largest oval we will fit a gas heater to, and the one with a covered terrace built into the shell. Three metres across rather than 2.4, with the roof carried out over a seating area at the front — so the cooling-off part of the session happens under cover, in a British garden, in October.

Same construction as the rest of the range: 42 mm thermowood side walls, thermo-aspen benches, and a two-room layout with a proper changing room. The terrace end carries a built-in log store under the curve of the shell — which is exactly where you want the wood if you are running it on a stove.

The layout is the point

The Kaari 300 is divided into two rooms with the heater on the dividing wall, and the terrace beyond that again.

The whole shell is around 19 m³. Heat all of that and you are into 12–18 kW territory and an electrical supply to match. Because it is partitioned, the heated room is about 9 m³ — a size a normal heater handles properly, and the largest room in our oval range that an off-grid gas heater will still serve.

The changing room stays cool, so the hot room stays hot when people come and go. With six people using it in rounds, that is the difference between a sauna that holds temperature and one that never quite recovers.

Why thermowood matters here

The body is thermowood throughout — timber kiln-treated at 180–220°C in a low-oxygen chamber. That is not a surface coating. It changes the wood itself, closing the cells so it absorbs far less moisture, which is what stops outdoor timber cupping, twisting and splitting through a British winter. No chemical preservatives are involved, and it weathers to a stable silver-brown rather than going grey and rough.

On a building this size with a projecting terrace roof, dimensional stability is not a luxury. There is a great deal more timber here than on a compact cabin, and proportionally more to gain from wood that does not move.

Specification

What's in the box

Everything structural. No hidden extras to buy before you can build it:

• Thermowood shell panels, pre-cut and numbered
• Thermo-aspen benches
• Porthole timber door and Ø 900 mm round front window
• Covered terrace structure, decking and integrated log store
• Bitumen roof shingles in your chosen colour
• Floor and foundation beams
• Stainless steel bands and complete fixing kit
• Fascia boards and ventilation grids
• Step-by-step assembly instructions

Run it on gas — no electrician, no cable across the garden

This is the option almost nobody else offers, and for a lot of gardens it is the one that makes a sauna possible at all.

A FinSteam gas heater runs on a standard propane bottle — the same sort you would use for a patio heater or a barbecue. No armoured cable, no trench across the lawn, no electrician quote you had not budgeted for. If your garden has no power at the far end, this is how you still get a sauna there.

The partition is what makes gas viable at this size. At around 9 m³ the heated room is at the top of what a single 8.1 kW heater serves well — which is exactly why the Kaari 300 is the largest oval we offer it on. Anything bigger and we would be overselling it.

Pick a gas option above and we fit the flue and commission the heater on installation day. You do not need to arrange anything with anyone.

Which gas option?

And then: safety pack, or without?

Every gas option includes the heater, the Orbis stone cage, and our fitting and commissioning. See the full gas heater range →

Or choose electric or wood-fired above

Electric — a Harvia floor-standing heater with a full stone load for soft, steady löyly, integrated controls and a 2-year warranty. At 9 m³ you want the 8 kW; check your supply can carry it. Needs a dedicated circuit installed by a qualified electrician, so budget £400–£1,200 for a garden supply on top of the heater.

Wood-fired — a Harvia M-series stove. No electrics at all, a real fire, and arguably the right answer on a sauna with a terrace to sit out on. We fit the flue on installation day. If you are in a smoke control area, check the model against DEFRA's exempt appliance register first — see our smoke control area guide.

2-year warranty

Two years on the structure and on the heater, whichever heat source you choose. Covers manufacturing defects and workmanship.

Lead time — please ask before you order

Lead times vary with stock and specification — anything from 2 to 12 weeks. Ask us before you commit and we will give you the real date for the exact build you want, not an optimistic one.

Getting it into your garden

This is the biggest oval in the range at 3 m wide and around 1700 kg, so the access conversation matters. It arrives flat-packed on long pallets that need a driveway or hard standing to be set down on — a pallet truck will not cross a lawn. Individual panels carry through a standard side gate, but measure the narrowest point of the route, including gate posts and downpipes, before you order.

At this weight it wants a concrete slab rather than paving on gravel, level and draining away from the timber. Our construction service starts at £500, and we apply insulating paste between every panel as we build, which is the single biggest factor in whether a sauna holds its heat properly. Full installation guide.

Send us photographs of the access route before you order. We would far rather tell you it will not fit than have it turn up and go back on the lorry.

Options

Choose your heater above. Roof shingles come in black, red, green or brown — tell us your preference when you order. Ask us anything before you commit.

Images are manufacturer renders and photographs of installed builds. The heater shown is illustrative — your heater choice is made above.