A sauna in a hotel, spa or holiday resort is hot for many hours a day, and more people sit on its benches in a week than in a home sauna in a year. That is why it pays to choose the wood species, profile, surface treatment and maintenance plan for the interior cladding together, at the design stage. This guide covers the questions developers, architects and sauna builders ask us most often.
How is a hotel sauna different from a home sauna?
In a hospitality sauna, the wood is put under strain for three reasons:
- Operating hours. The sauna may be heated all day or even continuously. Temperature and humidity change quickly every time water is thrown on the stones.
- Cleaning. Surfaces are washed more often than at home, so the finish has to withstand washing and the wood has to dry quickly.
- Appearance. The sauna has to look clean and tidy year after year, and the same wooden look often continues from the washrooms to the lobby.
Choose the wood species for the way the sauna is used
Wood species for saunas are free of resin, or have had the resin removed by thermal modification. They conduct heat slowly, so the surface does not get too hot against the skin.
- Spruce is a light, affordable standard choice for sauna walls and ceilings. A sauna protective finish protects it against moisture and dirt.
- Aspen and alder are resin-free hardwoods. Aspen is almost white and very even; alder has a warm reddish-brown tone.
- Thermally modified species, such as thermo pine, thermo aspen, thermo alder and thermally modified radiata pine, are dimensionally stable and dark. Thermal modification is carried out at high temperature using steam, and it removes the resin from the wood.
Continuously heated sauna: thermally modified aspen is not suitable for a continuously heated sauna. Choose thermally modified alder instead – its tone is close to thermo aspen – or thermally modified radiata pine, which we offer in a wide range of products.
Thermally modified radiata pine: newly installed radiata pine can have a strong smell at first. Ventilate the sauna well before opening it to guests, and the smell will fade.
Avoid untreated pine. Resin seeps out when the surface heats up.
See our wood species suitability table for which species suit which spaces.
Profile and direction define the look
Narrow panels create a rhythmic surface, wide panels a calm one. You can combine different widths and species in the same space. A batten panel looks like separate battens but installs like a panel, which speeds up cladding large surfaces such as ceilings.
The profile determines how light and shadow fall on the surface.
Panels can be installed horizontally, vertically or diagonally, and you can change direction within a surface. On ceilings, run the panels in the direction of the light so the joints are less visible.
Diagonal, vertical or horizontal – the direction changes the feel of the room.
Factory finishing saves time on site
For a large project, order the panels with the surface treatment already applied. We treat the wood in our own industrial paint shop right after planing, while the surface is open and absorbs the finish effectively.
- Sauna protective finish helps sauna surfaces withstand high temperatures and humidity, and keeps them easier to clean. It can also be tinted.
- Semi-transparent stain gives the wood a tone but leaves the grain visible. Use it to carry the same tone into changing rooms and the lobby.
- Tongues and edges are treated too. When the wood shrinks in the dry season, no untreated stripes appear at the joints.
- An even finish across the whole project. Under controlled conditions every panel gets the same treatment, so the tone stays consistent from floor to floor.
We treat batches of at least 500 metres at a time, which suits the quantities of hotel and spa projects. Spaces outside the sauna, such as corridors and lobbies, may have stricter fire safety requirements. With fire-retardant treatment, a wooden surface reaches fire class B-s1, d0 – the highest class possible for wood building products. Fire-retardant treatment cannot be used inside the sauna itself, as there is no fire-retardant product suited to sauna conditions.
When panels are treated before installation, the tongues get treated too.
One wooden look from the sauna to the lobby
When you use the same wood species in the sauna, washrooms and lobby, the spaces connect naturally. In the sauna, the panels are treated with a sauna protective finish or paraffin oil; in dry spaces with a semi-transparent or opaque finish. Match the benches to the tone, width and direction of the wall panels. Bench boards and battens of the same species also work for benches, shelves and other furniture.
Example combinations:
Installation for heavy use
- Let the panels acclimatise in the installation space for 1–2 weeks before installation, at about +20 °C and 40–60% relative humidity. Wet work such as levelling and tiling raises humidity, so do not store panels in the same space while it is going on.
- Leave a ventilation gap between the panels and the vapour barrier. Leave a small gap at the bottom of the wall and leave out mouldings at the wall-ceiling joint so air can circulate behind the panels.
- Allow for movement. Wood moves more in a sauna, so leave a gap of about 15 mm between the panel and the adjacent wall.
- Install horizontal panels tongue up so moisture cannot get into the groove.
- Use stainless steel fixings whatever the species. Fix thermally modified panels with a nail gun so they do not split.
- Fix bench supports to the wall battens or to extra supports behind the panels – never to the panelling alone.
Battens always run at right angles to the panels, at most 600 mm apart.
Maintenance in heavy use
A sauna that dries well lasts longest. Train your staff in these routines:
- Dry the sauna after every period of use. Keep the heater on for at least 30 minutes, with the door closed, the exhaust vent open and mechanical ventilation running.
- Do not hose down the walls every day. Wash the panels according to use – more often when the sauna is busy. Use a mild sauna cleaner and a soft brush along the grain. Do not use chlorine-based products or a pressure washer.
- Renew the surface treatment in time, preferably every year. Spruce, aspen and alder: sauna protective finish or paraffin oil. Thermally modified species: paraffin oil.
- Treat the benches with paraffin oil or sauna wax. Benches in a busy sauna need treatment more often.
When the sauna dries after use, the wood stays beautiful for years.
Checklist for designers
- Is the sauna continuously heated? If so, choose the species accordingly.
- Which species and tone continue from the sauna to the washrooms and lobby?
- Profile, width and direction for walls and ceilings.
- Factory finishing: sauna protective finish, semi-transparent stain, fire-retardant treatment for spaces outside the sauna.
- Quantity plus 10–15% waste allowance.
- Fixings, ventilation gaps and bench supports.
- Maintenance instructions for staff.
Talk to our sales team
We supply wood for visible surfaces to contractors, sauna builders and designers in Finland and abroad. We send samples of wood species and finishes, and help you calculate quantities. Contact our sales team or browse the product catalogue.