Steam & Oak Tallin 385 XL Outdoor Sauna — 4–6 Person, Changing Room & Terrace - Thermowood / Wood-fired — Harvia M series

Nearly four metres of cabin, divided into a hot room, a changing room and a covered front terrace — with two glass doors between them. At 21 m³ the Tallin 385 XL is the largest sauna we list, and the point at which a garden sauna becomes a building you spend an evening in rather than twenty minutes. The proportions are what make it work. It is only 2.31 m wide, so it reads as a long, low pavilion rather than a shed. The terrace is under the same roof, so the cooling-off part of a session happens in shelter. And the changing room between the heat and the outside means the hot room stays hot every time somebody comes and goes. Spruce or thermowood — your choice Nordic spruce is the traditional sauna timber: pale, clean-grained and bright inside. It is the more affordable build, and outdoors it needs treating and re-treating to stay looking new. Thermowood is 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. It arrives a deep honey-brown and weathers to a stable silver. On a cabin this size the thermowood upgrade is worth serious thought. There is simply more timber exposed to the weather than on anything else in the range, so there is more to gain from it — and more to maintain if you do not. Choose your timber above. The benches follow the shell: alder with spruce, thermo-aspen with thermowood. Specification Capacity 4–6 people Layout Hot room + changing room + covered front terrace External size 3850 mm long × 2310 mm wide × 2360 mm high Interior 1996 mm hot room + 1116 mm changing room + 578 mm terrace Sauna room volume approx. 21 m³ Weight approx. 1,250 kg Side walls 42 mm Back wall 28 mm Doors 2 × tempered bronze glass, 1890 × 690 mm Benches Alder (spruce build) or thermo-aspen (thermowood build) Roof Bitumen shingles — black, red, green or brown Delivery 1 pallet, 400 × 120 × 120 cm What is in the box Everything structural, including both glass doors and the terrace. No hidden extras to buy before you can build it: Cabin panels in your chosen timber, pre-cut and numbered Two tempered bronze glass doors Front terrace with benches and floor Sauna benches Floor Bitumen roof shingles and fascia boards Foundation cradles Heater guard Stainless steel bands and complete fixing kit Ventilation grids Step-by-step assembly instructions Heating a 21 m³ room — read this before you choose This is a big room, and we would rather be straight with you about what it needs than sell you something that will disappoint. Wood-fired — Harvia M seriesour recommendation The natural choice at this size. A wood stove handles the volume comfortably, needs no electrical supply at all, and the flue running through the changing room keeps it warm too. Chimney and stones included. Harvia Wall 8 kW Rated 7–12 m³ — well below this room's volume. Listed only for completeness. It will heat the room eventually in mild weather, but it is not the right specification and we would not fit it without talking to you first. No heater — cabin only Supply-only. The sensible choice if you want a properly sized electric unit, which we can source for you. For electric at this size, talk to us. A 21 m³ room wants considerably more output than the wall-mounted units we list as standard, and getting it wrong means a sauna that never quite gets there. We would rather specify it properly with you. All electric heaters must be installed and connected by a qualified electrician. Wood-fired installations are completed and the flue checked by our fitters. Gas on the 385 XL — ask us Our standard FinSteam gas heaters are 8.1 kW, which is the right output for cabins up to around 12 m³. One of them will not heat 21 m³ properly, so we do not list gas as a straightforward option here. It is still very much possible. A twin-heater configuration works — we already build twin 8.1 kW installations for commercial use — and there is a larger single FinSteam heater expected later this year which would suit this cabin on its own. If you want the Tallin 385 XL running off-grid on propane, with no cable across the garden, get in touch and we will price it for your site. See the current gas heater range → 2-year warranty The Tallin 385 XL carries a 2-year warranty on the cabin structure, and the heaters carry their own manufacturer warranty. Timber is stable and long-lasting outdoors, but like any outdoor structure it lasts longest if you treat the exterior and keep it treated — more so with spruce than thermowood, and more so on a cabin this size. We will tell you exactly what to use and when. Lead time — please ask before you order Lead time depends on stock and specification, and it moves. Depending on what is already built and how the factories are running, it can be anywhere from a couple of weeks to around four months.

Product information updated: 29 Oct 2026