Steam & Oak
Steam & Oak Kaari 240 Sauna Pod — 4–6 Person Thermowood with Round Window
Steam & Oak Kaari 240 Sauna Pod — 4–6 Person Thermowood with Round Window
Couldn't load pickup availability
The Kaari 240 is the one people point at. A curved oval shell, a Ø900 round window set into the front, and a solid timber door with three portholes down it — it looks like a hobbit house and it is meant to.
Underneath the character it is a properly specified Estonian sauna: 42 mm thermowood side walls, thermo-aspen benches, and a two-room layout that puts a hot room and a changing room inside a single 4.06 m building.
The layout is the point
The Kaari 240 is divided into two rooms with the heater sitting on the dividing wall. That matters more than it sounds.
A single-volume shell this size would be roughly 15 m³ of air to heat — which is why saunas of this length are often quoted with 12–18 kW heaters and a matching electrical bill. Splitting it means the heated room is around 7 m³: it comes up to temperature quickly, holds it, and runs on a sensibly sized heater. The other half stays cool as a changing and cooling space, so the hot room stays hot when someone opens the door.
The honest number is 4–6 people in the hot room. You will see this shell advertised elsewhere as an eight-to-ten person sauna. That figure only works if you count the whole building including the changing room — and heat all of it.
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 curved building this matters more than on a square one. Every board in an oval shell is doing structural work as part of the curve, and timber that moves is timber that opens gaps. Thermowood is the reason the shape stays true.
Specification
| Capacity | 4–6 people in the hot room |
| External size | 4060 mm L × 2400 mm W × 2480 mm H |
| Layout | Two rooms of approx. 1935 mm each — heater on the divider |
| Heated volume | approx. 7 m³ (total shell approx. 15 m³) |
| Side walls | 42 mm thermowood |
| Rear wall | 28 mm thermowood |
| Front window | Ø 900 mm round |
| Door | Solid timber with three round porthole windows |
| Benches | Thermo-aspen — stays cool to the touch at temperature |
| Roof | Bitumen shingles — black, red, green or brown |
| Bands | Stainless steel |
| Weight | approx. 1450 kg |
| Delivery | 1 pallet, 500 × 120 × 120 cm |
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
- 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 partitioned layout is what makes gas work on a building this size. At around 7 m³ the heated room sits comfortably inside the 8.1 kW envelope — a single-volume 15 m³ shell would not.
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?
| Botnia 81 | Our standard 8.1 kW gas heater. Everything you need to run the sauna. |
| Aurora 81 | The premium version of the same 8.1 kW heater — better finish and detailing. |
And then: safety pack, or without?
|
With safety pack recommended if children or guests use it |
Adds the Njord heat shield and the Halo guard rail. The heat shield cuts the required clearance to combustible timber from 200 mm to 50 mm, which gives you far more freedom in where the heater sits against a curved wall. The guard rail stops anyone brushing against the hot stones. |
| Without safety pack | Heater and stone cage only. Suits an install where clearance is generous and the sauna is for your own use. |
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. Needs a dedicated circuit installed by a qualified electrician; budget £400–£1,200 for a garden supply on top of the heater.
Wood-fired — a Harvia M-series stove, and the configuration this shell was originally drawn around. No electrics at all, a real fire, and the traditional way to run a sauna this size. 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
The Kaari 240 arrives flat-packed on a single 5 m pallet weighing around 1450 kg. That is a long pallet, so the delivery lorry needs somewhere firm to set it down — a driveway or hard standing, not a lawn. Individual panels carry through a standard side gate, but check the route for tight corners before you order.
It needs a level, load-bearing, well-draining base — paving slabs on a compacted sub-base or a concrete pad. At this weight we would recommend a slab. 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.
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. The heater shown is illustrative — your heater choice is made above.
Share
