Thermasol Luxury Saunas - Fortis

The Fortis is our flagship outdoor sauna — an enclosed, light-filled retreat engineered to sit in the open weather and stay beautiful through it. Its eave-style roofline and full smoked-glass front give it the presence of architecture rather than a garden appliance, while multi-layer wood-fibre insulation holds heat efficiently from the first cold morning of the season to the last.

Built from thermally treated Nordic Spruce and Aspen, the Fortis resists moisture movement and stays dimensionally stable outdoors where ordinary softwood twists. It arrives with a Harvia Virta 8 kW heater and integrated LED lighting on smart control, so the room is warm and ready from your phone before you walk out to it. Comfortably seats three to four bathers.

Placement is the first real decision. The Fortis wants a level, load-bearing base — a concrete pad, reinforced deck, or compacted gravel bed — with clearance on the service side for the heater's electrical run. Because the glass front is the room's face, most owners orient it toward the garden's long view and let the insulated back wall take the weather. The eave roofline sheds rain and snow without gutters, so siting under deciduous trees costs you nothing but sweeping.

Power is straightforward for an electrician: the Harvia Virta 8 kW runs on a dedicated 240 V circuit, sized and quoted before anything ships. Heat-up from cold sits around forty-five minutes in winter air, faster in season, and the multi-layer wood-fibre insulation is what keeps the running cost honest — the room holds temperature between rounds instead of bleeding it through the walls.

A session in the Fortis follows the classic rhythm: fifteen to twenty minutes at 80–90°C, a cold rinse or plunge, ten minutes of air, repeat. The smoked Parasol® glass keeps the interior private in daylight while the LED scene turns the room into a lantern after dark — the reason this build anchors evening rituals as often as morning ones.

Care is seasonal rather than weekly. Rinse and squeegee the glass, oil the exterior once a year if you want to hold the original tone (or let it silver — the timber doesn't care), and vacuum the heater compartment before each cold season. The thermally treated Spruce and Aspen don't ask for preservatives; heat treatment already closed the grain.

Who is it for? The Fortis is the build we quote when the sauna is the centrepiece of a landscape plan rather than an addition to it — courtyard gardens, lake frontage, rooftop terraces engineered for the load. Buyers cross-shopping it usually compare against site-built custom rooms; the difference is that the Fortis arrives finished, insured, and warrantied as a product rather than a project, typically at a fraction of an architect-led build's timeline.

Delivery and lead time work like the rest of the line: the build is crated at the factory, freight is quoted to your address in the same document as the sauna itself, and a consultant confirms access — gate widths, crane need, surface — before anything ships. From deposit to first session most Fortis installs land inside a season, not a year.

The seasonal argument for a build like this is simple: winter is when a sauna earns its place, and winter is exactly when lesser outdoor rooms disappoint — condensation in the walls, heat bleeding through thin cladding, glass that frosts from the inside. The Fortis's insulated envelope and smoked glazing were specified against a Nordic January, which is why a February session feels like the room's natural habitat rather than a test it's passing.

There's also a property dimension owners mention after the fact: a permanent, architect-grade sauna reads as landscape investment, not garden equipment. Appraisers treat an insulated outdoor room with a warranted structure very differently from a kit shed — and the Fortis photographs like the former because it is.

A private, light-filled outdoor room — modern eave roofline, glass front, and insulated walls that hold their heat through every season.

• Seats 3–4 bathers
• Multi-layer wood-fibre insulated walls
• Weather-rated roof with smoked Parasol® glass
• Smart controls with integrated LED lighting
• Thermally treated Nordic spruce and aspen construction
• Ships with a Harvia Virta 8 kW heater