Steam & Oak Pärnu L Outdoor Sauna — 3–4 Person Thermowood, Corner Glass & Insulated Roof

Most garden saunas are a timber box with a door in it. The Pärnu L is a designed object: black-framed glass across the entire front, black trim, black bench fronts, and warm thermowood everywhere the eye lands. It is the one you put where people can see it, not down the end of the garden behind the shed.

At 2.29 m square it is the larger of the pair, with glass wrapping the corner rather than sitting flat across the front — so the view opens up as you sit down. Four people fit on a proper two-level bench. It comes with its own thermowood decking and ground frame, so it stands correctly on almost any level surface without you building a base for it.

Usually the quickest sauna we can get you

Most cabins in our Estonian range are made to order, and lead times run to several months when the factory is busy. The Pärnu is built on a different line and is often available in around six weeks — sometimes from stock.

If you want a sauna this season rather than next, this is the one to ask about first. Tell us when you want it and we will tell you honestly whether it is achievable.

Built like a building, not a kit

40 mm thermowood walls, and a roof insulated with 30 mm Kingspan under 18 mm thermowood boards — a warm roof in the building sense, not just a covered one. That is unusual at this size and it is why the room holds heat the way it does. Thermowood is timber kiln-treated at 180–220°C in a low-oxygen chamber: not a coating, but a change to the wood itself that closes the cells so it absorbs far less moisture. That is what stops outdoor timber cupping, twisting and splitting through a British winter, and it happens without chemical preservatives.

The floor and decking are 28 mm thermowood. The ground frame is pressure-treated. The trimming boards, bench fronts and backrest are painted black as standard — this is a finished product, not a shell you have to decorate.

Specification

What is in the box

Everything structural and every piece of trim. No hidden extras to buy before you can build it:

• 40 mm thermowood wall panels
• Insulated roof — 30 mm Kingspan with thermowood inner boards
• Thermowood decking and 28 mm floor
• Pressure-treated ground frame (44 × 90)
• Two-level thermo-aspen benches with black-painted fronts
• Thermo-aspen backrest, painted black
• Tempered bronze glass door and window
• Black trimming boards throughout
• Self-adhesive roofing felt and black metal flashing
• Screws and fixings
• Assembly instructions

Running it on gas

The FinSteam gas heater is flueless, so nothing needs to pass through the insulated roof. Like every gas sauna we build, it needs two ventilation openings through the walls: a fresh air inlet low beside the heater and an exhaust high in the opposite corner. The Pärnu L has the same 40 mm thermowood walls as the Pärnu S, which takes gas without difficulty.

We are finalising the gas configuration for this model. If you want to run it off a propane bottle with no electrician and no cable across the garden, ask us and we will confirm the setup and price. In the meantime see the gas heater range.

Or choose an electric heater

The Pärnu L takes a wall-mounted heater, which keeps the bench and floor space usable. Our Harvia Wall is black steel with a full 20 kg stone capacity for softer, steadier löyly, integrated controls and a 2-year warranty — and black steel is exactly right in this interior.

Not sure which? Ask us. This room is unusually well insulated for its size, so it does not need as much output as the volume suggests — we will match it properly rather than sell you the biggest one.

All electric heaters must be installed and connected by a qualified electrician. We confirm the exact supply requirement with you before installation.

Prefer a different heater, HUUM or a WiFi-controlled model? Choose cabin only and talk to us; we can supply and fit most makes.

Wood-fired on the Pärnu L

A wood-burning stove is possible on this cabin, and at 6.3 m³ the room sits right at the bottom of the range the smaller sauna stoves are rated for, so it will run hot and you control it by how much you feed it.

The flue does not go through the insulated roof. It exits through the 40 mm thermowood wall behind the stove, then an insulated twin-wall chimney rises outside the cabin and finishes above the roof line, clear of the glass door and window. That keeps the warm roof intact and keeps the hot section of the chimney outside the room.

Bear in mind a stove takes a corner away from the glass, so the cabin becomes a comfortable two to three person sauna rather than three to four, and a non-combustible hearth goes down on the thermowood floor under and in front of the stove. We recommend the flue is fitted by a HETAS registered installer.

Choose cabin only and ask us. We will confirm the stove, the flue kit and the price for your build.

2-year warranty

The Pärnu L carries a 2-year warranty on the cabin structure, and the heaters carry their own manufacturer warranty.

Thermowood is stable and rot-resistant by nature, but like any outdoor timber it lasts longest if you treat the exterior and keep it treated. The black trim in particular repays maintenance. We will tell you exactly what to use and when.

Lead time — ask us, this one is usually quick

Unlike most of the range, the Pärnu is often available in around six weeks, and sometimes from stock. That said, lead times move with demand and specification.

Ask us and we will give you the real date for your build before you commit — we would rather tell you the honest timescale up front than quote a comfortable number and disappoint you later.

Getting it into your garden

• Base: level and well-drained. The pressure-treated ground frame is included, so a slab, paving or compacted gravel is all you need underneath. Allow 229 × 229 cm plus room to walk around it.
• Access: delivered flat-packed, so the parts go through a standard side gate. No crane, no dismantling fences.
• Assembly: typically a day for two people, or leave it to our installation team.
• Sequence: most customers build the cabin first, then have the heater and lighting connected once it is in position.

Options

• Exterior timber-protection finishes
• Sauna accessory sets