Sauna Cladding
Premium sauna cladding for walls and ceilings, engineered for heat and humidity. Finnmark stocks Aspen, Alder, and thermo-treated Nordic timber in a comprehensive range of tongue-and-groove profiles – from clean-lined STS4 panels to textured STEP and ROMBTO feature boards. Every board is selected specifically for sauna use: low resin, low thermal conductivity, and a minimum 14 mm thickness to meet the Finnish standard for sauna construction.
Whether you’re lining a DIY home sauna, fitting out a garden sauna cabin, or specifying timber for a commercial wellness project, you’ll find the right species, profile, and length here – backed by free expert guidance from our team of 40+ sauna specialists.
Looking to learn more about sauna wood? Read our dedicated guide: Best Wood for Saunas (& Why).
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Aspen Sauna Cladding
Aspen is the benchmark timber in Finnish sauna construction. It has a pale, creamy colour with a fine, even grain and very few knots, giving walls and ceilings a clean, contemporary finish. Aspen has naturally low thermal conductivity, so the wood surface stays comfortable to the touch at high sauna temperatures. It is virtually resin-free, meaning there is no risk of sticky deposits forming during use. For those building a traditional Nordic sauna interior with a light, bright aesthetic, Aspen is the go-to choice.
Alder Sauna Cladding
Alder offers a warmer, honey-toned alternative to Aspen. It has a smooth, uniform grain and handles repeated heating and cooling cycles with minimal movement. Like Aspen, Alder has low resin content and low heat absorption, making it comfortable against bare skin. Over time, it develops a gentle patina that many sauna owners find attractive. Alder is one of the most popular sauna timbers across Scandinavia and the Baltic states, used in both residential and commercial builds.
Thermo-Treated Sauna Cladding
Thermally modified timber – including Thermo Aspen, Thermo Alder, and Dark Thermo Alder – is heat-treated at temperatures above 180°C in a controlled, oxygen-free process. This permanently alters the wood’s cell structure, delivering improved dimensional stability, greater resistance to moisture absorption, and enhanced durability. Thermo-treated cladding is significantly less prone to warping, cupping, and swelling than untreated timber, and it develops a richer, deeper colour tone.
Spruce, Cedar & Specialist Timbers
Spruce is a traditional Nordic sauna timber with a light colour and characteristic knotty grain – a cost-effective option for a more rustic interior. Western Red Cedar offers natural decay resistance and a rich, aromatic scent, valued particularly for exterior sauna cladding. Finnmark also stocks Thermo Radiata Pine and decorative Juniper panels for accent walls and feature details.
Sauna Cladding Profiles Explained
The profile of your sauna cladding determines how each board connects to the next and the visual effect it creates on the finished surface. Finnmark stocks a full range of profiles from Thermory and other leading Nordic manufacturers, each designed specifically for sauna environments.
STS4 is the most popular profile in our range. It features a tongue-and-groove connection with a subtle shadow line between boards, creating a clean, linear appearance that suits both contemporary and traditional sauna designs. Available across most species in widths of 90 mm, 120 mm, and 140 mm.
STP is a flat-face tongue-and-groove profile that produces a smooth, seamless surface with minimal shadow gap. Ideal for a sleek, uninterrupted wall finish, and works particularly well on ceilings.
STEP features a distinctive stepped edge that creates a pronounced shadow line between boards. Available in a narrower 64 mm width, this profile adds depth and visual interest for a more textured, detailed appearance.
VALEURA offers a wider groove for a more defined shadow effect. ROMBTO introduces an angular, diamond-shaped surface for striking feature walls. KYTE profiles provide an asymmetric design with clean, modern lines.
Design guidance: STS4 and STP for understated, timeless interiors. STEP and VALEURA for added texture and shadow. ROMBTO or KYTE for bold architectural statements.
Sauna Cladding Specification
Getting the specification right ensures your sauna cladding performs well and lasts. The following guidelines apply to all interior sauna wall and ceiling applications.
- Thickness: Use boards ≥14 mm thick (the Finnish legal minimum for sauna timber) to avoid movement under heat and humidity cycling.
- Widths: 90 mm, 120 mm, and 140 mm are the standard options – choose based on the visual proportion you want and the scale of the room.
- Lengths: Most profiles are stocked in 2100 mm and 2400 mm. The 2100 mm length suits standard wall heights; 2400 mm is ideal for ceiling runs and taller rooms.
- System build-up: Plan thermal insulation and vapour sealing, and ventilated battens behind the cladding to protect the structure and allow the timber to dry between sessions.
- Bench matching: If you’re matching your sauna benches, aim for ~28 mm bench timber (SHP profile) in the same species for a consistent tone across the room.
FSC®/PEFC options available across core species.
Unsure which option is right for you? Our team of sauna specialists are on hand for free, expert guidance at any time in your build.
Everything You Need to Build a Sauna
A great sauna is a system. Your sauna cladding performs best when the surrounding components match its standard – so the room looks cohesive, handles heat and humidity, and stays easy to maintain.
Trims & Feature Surfaces
- Corner mouldings & edge trims: matching species and sizes for neat terminations and consistent shadow lines across walls and ceilings.
- Sauna feature wall panels: controlled texture and natural aesthetics that complement your main boards without complicating installation.
Heat Sources
- Electric sauna heaters: a broad range of kW outputs for different room volumes, with steady heat delivery and straightforward integration.
- Wood-burning stoves: authentic Finnish warmth with models suited to compact barrels through to larger cabins.
Access & Lighting
- Sauna doors: quality glass options that align with your cladding tone for a clean, modern look.
- Sauna lighting: IP-rated fittings and accent options that highlight profile detail and maintain a calm, low-glare atmosphere.
Control & Monitoring
- Digital control panels: reliable temperature and schedule control for consistent sessions.
- Thermometers & hygrometers: clear, at-a-glance readings to keep heat and humidity in the comfort zone.
Sauna Bench Wood - FAQs
What is sauna cladding?
Sauna cladding is the interior wood panelling that lines sauna walls and ceilings to create a stable, heat-tolerant finish and protect the underlying structure. It forms the visible surface of the sauna room, manages heat and humidity with a ventilated cavity behind, and delivers a clean, durable interior.
Made from low-resin, low-conductivity softwoods (typically Aspen, Alder, and thermo-treated variants), sauna cladding stays comfortable to the touch and keeps maintenance simple.
What thickness should sauna wood cladding be?
Use boards of 14 mm or thicker for interior sauna cladding. Thinner stock is more prone to warping and cupping under repeated heat and humidity cycles. Typical widths are 90, 120, and 140 mm – choose a thickness and width combination that maintains span and keeps fixings discreet.
The 14 mm minimum is the Finnish legal standard for sauna timber, and all cladding in the Finnmark range meets or exceeds this specification.
What is the best wood for sauna cladding?
The best wood for sauna cladding depends on the look and performance you need. Choose softwoods with low heat transfer and minimal resin content:
- Aspen – pale, knot-light, comfortable to the touch. The most popular choice in Finnish sauna building.
- Alder – warm tone, smooth grain, reliable in regular use with an attractive natural patina over time.
- Thermo Aspen / Thermo Alder – thermally modified for improved stability, durability, and a richer colour. The premium choice for long-term performance.
Denser hardwoods are avoided for sauna cladding as they hold more heat and can feel uncomfortably hot against bare skin.
Should sauna cladding be installed vertically or horizontally?
Both orientations work well. Vertical installation emphasises ceiling height, creates tidy lines above benches, and can help shed condensation naturally. Horizontal installation visually widens smaller rooms and aligns neatly with benches and backrests. In either case, ensure a ventilated air gap behind the cladding for proper moisture management.
Can I stain or varnish sauna timber cladding?
No. Do not use any varnish, lacquer, or film-forming finish on sauna wood cladding. These products trap moisture, can become tacky at sauna temperatures, and may release harmful fumes when heated. For protection on high-touch areas, use a sauna-specific paraffin oil which is light, breathable, and designed for high-heat environments. Avoid household waxes, generic wood oils, and all synthetic coatings.
How do I clean and maintain sauna wood cladding?
After each session, ventilate the room thoroughly and allow the panels to dry naturally. Wipe splashes with a damp (not wet) cloth, working with the grain. Periodically clean with a sauna-safe, pH-neutral cleaner, taking care not to soak the wood or force moisture behind the boards. Avoid pressure washing, steam cleaning, or any method that could saturate the timber. With proper ventilation and routine care, quality sauna cladding will maintain its appearance for many years.
What is thermally modified sauna wood?
Thermally modified timber (also called thermo-treated or heat-treated wood) is produced by heating natural wood to temperatures above 180°C in a controlled, oxygen-free environment. This permanently alters the wood’s cell structure, reducing moisture absorption and significantly improving dimensional stability. The result is cladding that resists warping, cupping, and decay more effectively than untreated timber, with a deeper, richer colour. Finnmark stocks Thermo Aspen, Thermo Alder, Dark Thermo Alder, and Thermo Radiata Pine cladding profiles.
Do I need a vapour barrier behind sauna cladding?
Yes. A continuous aluminium vapour barrier should be installed behind the battens and cladding. This prevents steam and moisture from penetrating into the insulation and wall structure, protecting against damp, mould, and structural damage. The vapour barrier works with ventilated battens to allow the cladding to dry efficiently between sessions.
How much sauna cladding do I need?
Measure the total surface area of walls and ceiling (height × perimeter for walls, plus length × width for the ceiling). Subtract doors and windows, then add approximately 10% for cutting waste. Each product listing on the Finnmark website states coverage per pack, making it straightforward to calculate quantities. Need help? Get in touch for free, no-obligation guidance.