Exterior Cladding for Outdoor Saunas: Board & Batten, Shiplap, and Shou Sugi Ban Compared

When most people think about building or buying an outdoor sauna, they focus on what's inside — the heater, the bench layout, the wood species lining the hot room. But the exterior cladding is arguably just as important. It's the first line of defense against rain, snow, UV exposure, and temperature swings, and it plays a massive role in how long your sauna lasts and how good it looks in your backyard for years to come.

The cladding style you choose also defines the entire visual character of your sauna. A rustic board and batten finish tells a completely different story than the dramatic, jet-black surface of shou sugi ban charred wood. And a clean shiplap profile slots in perfectly alongside modern architecture. Beyond aesthetics, each cladding method carries its own performance characteristics when it comes to moisture management, thermal movement, maintenance demands, and longevity — all of which matter significantly in the uniquely demanding environment surrounding a sauna.

In this guide, we'll break down the three most popular exterior cladding styles for outdoor traditional saunas: board and batten, shiplap, and shou sugi ban. We'll cover what each one is, how it performs, what wood species work best with it, and how to decide which is right for your build.

Board and Batten: The Classic Vertical Cladding

What Is Board and Batten?

Board and batten is one of the oldest and most recognizable siding profiles in North American construction. The design is simple: wide vertical boards are installed side by side with narrow strips (the "battens") covering each seam where two boards meet. This creates a rhythmic, vertical pattern with pronounced shadow lines that give the exterior a strong sense of depth and dimension.

Historically, board and batten was a practical solution for barns and agricultural buildings because the battens sealed the gaps between boards, preventing wind and water infiltration without requiring tight-tolerance milling. That same practical ingenuity makes it an excellent choice for cabin-style saunas and custom builds where a rustic, handcrafted aesthetic is desired.

Performance Characteristics for Saunas

One of board and batten's greatest strengths in a sauna application is its tolerance for wood movement. Because the wide boards are not interlocked or tongue-and-groove joined, they can expand and contract seasonally without buckling. The battens cover the gaps and accommodate this movement while still maintaining a weather-tight seal. This is particularly valuable for outdoor saunas, which experience extreme temperature differentials — the interior might reach 185°F or higher while the exterior faces freezing winter conditions.

From a moisture management perspective, the vertical orientation is a natural advantage. Water runs straight down the face of the cladding with gravity, rather than pooling in horizontal seams. This means less standing water, less potential for rot, and faster drying after rainfall. For sauna owners in snowy or wet climates, this is a significant practical benefit.

Board and batten does require proper detailing to perform well. The boards should be back-primed or sealed before installation to prevent moisture from wicking in from behind. Using stainless steel or hot-dipped galvanized fasteners is essential, as the temperature cycling near a sauna wall will accelerate corrosion in lesser hardware. A rain screen gap behind the boards — even just 3/8" of air space — can dramatically improve drying potential and extend the life of the cladding.

Best Wood Species for Board and Batten Sauna Cladding

Western red cedar is the traditional go-to for board and batten on saunas, thanks to its natural resistance to decay, dimensional stability, and warm reddish tone. It weathers to a beautiful silver-gray patina if left untreated, or it can be maintained with a penetrating oil finish to preserve the original color. Cedar sauna wood contains natural oils called thujaplicins that act as preservatives, giving it genuine rot resistance without chemical treatment.

For enhanced durability, thermally modified wood (thermowood) is an increasingly popular upgrade. Species like thermo-spruce or thermo-pine undergo a heat treatment process between 356°F and 482°F in an oxygen-free environment. This fundamentally alters the wood at a cellular level, dramatically reducing its ability to absorb moisture and making it far more resistant to rot, warping, and insect damage than untreated lumber. Thermowood's deep brown color and consistent appearance make it a premium choice for board and batten cladding on thermowood saunas.

Pine and spruce can also work as more budget-friendly options when properly stained or treated, though they will require more frequent maintenance in exposed outdoor applications.

Aesthetic and Design Considerations

Board and batten delivers a distinctly vertical visual rhythm that makes saunas appear taller and more grounded. It's a natural fit for cabin-style saunas and structures that lean into a Scandinavian or rustic North American aesthetic. Brands like True North Saunas and Dundalk LeisureCraft, which specialize in handcrafted Canadian-made outdoor saunas, often incorporate vertical board profiles on their cabin sauna models for this very reason.

You can vary the look significantly by adjusting board widths, batten widths, and the depth of reveal between them. Wider boards with narrow battens create a more modern, streamlined look. Mixing board widths or using rough-sawn lumber adds rustic character. The cladding can also be stained in a wide range of colors — from natural wood tones to black or charcoal finishes that mimic the look of shou sugi ban without the charring process.

Shiplap: The Clean, Horizontal Profile

What Is Shiplap?

Shiplap is a type of wooden board with a rabbet (a stepped notch) cut into the top and bottom edges, allowing each board to overlap the one below it. When installed horizontally, these overlapping joints create a tight, weather-resistant seal with a characteristic thin shadow line between each course. The result is a clean, linear, horizontal pattern that reads as modern, refined, and architecturally intentional.

Unlike tongue-and-groove, which creates a flush joint, shiplap's overlap creates a small channel between boards. This is both an aesthetic feature (those shadow lines) and a functional one — the channel allows for some drainage and air movement between courses.

Performance Characteristics for Saunas

Shiplap's overlapping joint design is inherently good at shedding water. Each board laps over the one below it, which means water running down the face of the cladding is directed outward at each joint rather than finding a pathway inward. When installed with a slight downward angle on the exposed face, shiplap provides excellent rain protection for the wall structure behind it.

The tight joints also offer good wind resistance, which matters for saunas in exposed locations. Wind-driven rain is one of the most common sources of moisture intrusion in outdoor buildings, and shiplap's lapped joints handle it better than flat-butted board profiles.

One consideration with horizontal shiplap is that it doesn't shed water quite as efficiently as vertical profiles. Water can wick along the bottom edge of each board if the drip edge isn't properly detailed. This is easily managed with proper installation practices — ensuring a slight bevel on the exposed edge, maintaining adequate ground clearance (at least 6 to 8 inches from grade to the bottom of the cladding), and using appropriate flashing at the foundation line.

Shiplap also accommodates wood movement reasonably well. The rabbet joint allows boards to expand and contract within their lap without opening visible gaps or creating stress on fasteners. This is important for sauna exteriors where the temperature gradient from inside to outside can be extreme and can cause more thermal movement than a standard building wall would experience.

Best Wood Species for Shiplap Sauna Cladding

Cedar remains an excellent choice for shiplap sauna cladding, and it's one of the most commonly used species in this profile. Its low density, natural preservatives, and easy workability make it ideal for milling clean rabbet joints that fit together consistently. Many outdoor saunas from manufacturers like SaunaLife feature spruce shiplap or lap-style exterior cladding that provides a clean, modern appearance.

Thermally modified wood works exceptionally well in a shiplap profile. Because thermowood has significantly reduced moisture absorption (sometimes 40-50% less than untreated wood of the same species), the boards remain more dimensionally stable through seasonal changes. This means tighter joints, less gapping in winter, and less cupping in summer. Thermowood is widely considered one of the best wood choices for saunas precisely because of this enhanced stability. Brands like Auroom use thermally modified timber extensively in both interior and exterior sauna construction for this reason.

Siberian larch and accoya (acetylated wood) are additional premium options sometimes used for shiplap sauna cladding, though they come at a higher price point. Both offer exceptional durability and dimensional stability in exterior applications.

Aesthetic and Design Considerations

Shiplap is the go-to profile for contemporary and modern sauna designs. Its horizontal lines create a sense of width and low-slung elegance that complements flat or shed-style rooflines, large glass doors, and minimalist landscaping. If you've admired the clean-lined look of luxury outdoor saunas from brands like Haljas Houses or Auroom, shiplap-style exterior profiles are a big part of what gives them that refined, architectural feel.

Shiplap can be oriented vertically as well, which creates an entirely different visual effect — more modern and unexpected than traditional board and batten. Vertical shiplap with a narrow reveal is a contemporary Scandinavian detail that's gaining popularity in sauna design.

The profile is also versatile in terms of finish. It looks beautiful left to weather naturally, stained with a semi-transparent color, or finished with a solid-body stain. A black or dark charcoal stain on shiplap can give you the dramatic dark exterior look of shou sugi ban at a lower cost and with less specialized labor.

Shou Sugi Ban: The Art of Charred Wood

What Is Shou Sugi Ban?

Shou sugi ban (also called yakisugi) is a Japanese wood preservation technique that dates back to 18th-century Japan. The name translates roughly to "burnt cedar board." The process involves charring the surface of wooden planks with fire, then cooling, brushing, and finishing them with natural oil. What remains is a deeply textured, carbonized surface that is both visually striking and remarkably functional.

The technique was originally developed as a practical method to protect Japanese cedar (Cryptomeria japonica) used in building construction. Builders discovered that the charred surface layer created a natural barrier against moisture, insects, fire, and UV degradation — eliminating the need for chemical preservatives entirely. Today, shou sugi ban has been embraced by architects and builders worldwide as both a preservation method and a design statement, and it has found a particularly compelling application in outdoor sauna construction.

Performance Characteristics for Saunas

Shou sugi ban's performance benefits for outdoor saunas are substantial and well-documented. The charring process carbonizes the outer layer of the wood, fundamentally changing its cellular structure. This carbonized layer acts as a natural shield against multiple threats simultaneously.

Moisture resistance is perhaps the most important benefit for sauna applications. The charring process seals the wood's pores, dramatically reducing its ability to absorb water. This means less warping, less swelling, less rot — all critical concerns for a structure that generates enormous amounts of heat and humidity on the inside while being exposed to rain, snow, and freeze-thaw cycles on the outside.

The fire resistance of shou sugi ban may seem paradoxical — fighting fire with fire — but it's scientifically sound. The already-carbonized surface is far more resistant to ignition than raw wood. For saunas, especially those paired with wood-burning sauna heaters, this added fire resistance provides genuine peace of mind, particularly where the chimney or stovepipe exits through the wall or roof.

Insect and fungal resistance is another significant advantage. The charring process removes the organic compounds that attract wood-boring insects and fungal organisms. This makes shou sugi ban cladding extremely resilient in wooded, damp, or humid environments where untreated wood would be vulnerable to degradation.

UV resistance is often overlooked but matters a great deal for outdoor saunas. Untreated wood can gray, bleach, and crack under prolonged sun exposure. The deep black or dark brown surface of shou sugi ban is inherently more stable under UV exposure than natural wood surfaces, meaning the appearance holds up better over time with less maintenance.

With proper installation and occasional re-oiling (typically every 5 to 10 years for exterior applications), a shou sugi ban clad sauna can remain structurally sound and visually stunning for 50 years or more.

Best Wood Species for Shou Sugi Ban

Traditionally, shou sugi ban was performed exclusively on Japanese cedar (sugi), which is a softwood with a relatively low density that chars evenly and deeply. In Western applications, several species work well.

Western red cedar is the most popular choice for shou sugi ban in North America. It chars beautifully and evenly, its natural oils help it resist decay even before charring, and its low density (approximately 23 lbs per cubic foot) allows the fire to penetrate to an adequate depth without excessive burn time. If you're building a custom sauna, cedar shou sugi ban cladding is a proven and widely available option.

Cypress (particularly bald cypress) is another excellent candidate, valued for its superior rot resistance and fine, straight grain. Larch, pine, and hemlock can also be charred effectively, though hardwoods like oak require significantly more heat and may not achieve the same depth of char.

It's worth noting that some manufacturers now offer factory-produced alternatives that replicate the shou sugi ban aesthetic using thermal modification rather than open-flame charring. Companies like Thermory produce embossed, heat-treated cladding panels that capture the look of charred wood with the enhanced dimensional stability of thermowood. This can be an attractive option for those who want the visual impact of shou sugi ban with the performance consistency of thermally modified timber.

The Charring Process: DIY vs. Factory-Produced

Shou sugi ban can be done by hand using a propane torch, which makes it accessible for DIY sauna builders. The traditional Japanese method involved binding three boards together in a triangular column and lighting a fire at the base, but the modern single-board torch method is more practical for most projects.

Key considerations for DIY charring include selecting boards with a moisture content of 12-15% for even charring, maintaining a consistent torch distance and speed for uniform depth, and always performing the charring outdoors in a safe, fire-controlled environment. After charring, the boards are cooled with water, brushed to remove loose carbon (if a brushed finish is desired), and sealed with a natural oil like tung oil or linseed oil.

Factory-produced shou sugi ban boards offer more consistency and convenience but come at a premium. They're worth considering for visible, high-impact facades where uniformity matters. For a sauna — which is typically a smaller structure — the cost difference between DIY and factory boards is often manageable and may be worth the investment for a professional result.

Aesthetic and Design Considerations

There's nothing quite like the visual impact of a shou sugi ban-clad sauna. The deep black, textured surface creates a dramatic contrast against green landscapes, snow, or natural stone. It photographs beautifully, ages gracefully, and makes a bold architectural statement that few other materials can match.

The finish can vary significantly depending on the depth of char and the amount of brushing. A deep char with minimal brushing produces the most dramatic, alligator-skin texture with an almost matte-black finish. A lighter char with heavy brushing reveals more of the underlying wood grain, creating a dark brown or charcoal appearance with more visual warmth. Both approaches look stunning on outdoor saunas.

Shou sugi ban pairs exceptionally well with modern sauna designs — think flat rooflines, full-glass doors, and minimalist hardware. The contrast between the charred dark exterior and the light, clean interior wood (often aspen or alder) creates a powerful design tension that many custom sauna projects leverage to great effect.

Comparing the Three: Board & Batten vs. Shiplap vs. Shou Sugi Ban

Durability and Longevity

All three cladding styles can deliver excellent durability when properly installed with quality materials. Shou sugi ban has a slight edge in raw longevity — a properly charred and maintained cedar surface can last 50+ years with minimal intervention. Board and batten and shiplap in cedar or thermowood will typically deliver 25-40 years of service before requiring significant repair or replacement, depending on climate exposure and maintenance frequency.

The weakest link in any cladding system is usually the fasteners and flashing, not the wood itself. Use stainless steel ring-shank nails or screws, install proper head flashing above windows and doors, and ensure adequate ventilation behind the cladding, and all three profiles will serve you well for decades.

Maintenance Requirements

Shou sugi ban is the lowest-maintenance option of the three. The charred surface naturally resists UV degradation, moisture, and biological attack. A re-oiling every 5-10 years is typically all that's needed. Board and batten and shiplap in cedar will benefit from a penetrating oil or stain treatment every 2-4 years if you want to maintain the original wood color. If you prefer the natural silver-gray weathered look, you can largely leave them alone after ensuring the initial installation is sound.

Thermowood cladding in any profile falls somewhere between — its enhanced moisture resistance means less frequent maintenance than untreated wood, but it will still benefit from periodic oiling to maintain color.

Cost Considerations

Board and batten is generally the most cost-effective option, particularly when using locally available cedar or pine. The milling is simpler than shiplap, and installation is straightforward. Shiplap costs slightly more due to the precision milling required for the rabbet joints. Shou sugi ban is the most expensive of the three, whether you're purchasing factory-charred boards or factoring in the labor for DIY charring. However, its reduced long-term maintenance costs can offset the higher upfront investment over the life of the sauna.

For context, if you're exploring outdoor saunas at various price points, the cladding choice can impact the total project cost by 10-20%, making it worth considering alongside your decisions about sauna heaters and interior wood species.

Climate Suitability

All three cladding styles work in a wide range of climates, but each has subtle advantages in specific conditions. Board and batten excels in areas with heavy rainfall or snowfall thanks to its vertical orientation and superior water-shedding capability. Shiplap performs well in moderate climates and coastal environments where wind-driven rain is a concern. Shou sugi ban is arguably the most universally capable — its comprehensive resistance to moisture, UV, insects, and fire makes it suitable for everything from desert heat to northern winters.

If you're in a region with severe winters and heavy snow loads, reviewing options from manufacturers who specifically engineer their saunas for harsh conditions is wise. Brands like True North, whose handcrafted cabin saunas come standard with rain-proof roof membranes and protective fascia boards, understand the importance of weather-ready exterior construction.

Installation Tips for Any Cladding Style

Regardless of which cladding profile you choose, several universal best practices will maximize the performance and lifespan of your outdoor sauna's exterior.

Always incorporate a rain screen. A rain screen is simply an air gap (typically 3/8" to 3/4") between the cladding and the wall sheathing or vapor barrier. This gap allows any moisture that gets behind the cladding to drain down and evaporate, preventing it from being trapped against the wall structure. On a sauna, where interior humidity levels are extreme, this ventilation gap is even more critical than on a standard building. Use vertical furring strips to create the gap, and ensure there's a screened opening at both the bottom and top of the cladding to allow airflow.

Use appropriate vapor management. The interior side of an outdoor sauna wall should have an aluminum foil vapor barrier to keep steam and moisture inside the hot room. The exterior should be breathable — never use a non-permeable membrane behind the exterior cladding, as this can trap condensation within the wall assembly. A housewrap-type weather-resistant barrier (WRB) that allows water vapor to pass through while blocking liquid water is ideal.

Choose your fasteners carefully. Saunas create a more corrosive environment than typical construction due to heat and humidity cycling. Stainless steel fasteners are the gold standard. Hot-dipped galvanized is an acceptable alternative. Never use electroplated zinc fasteners — they'll corrode and fail prematurely, leaving rust streaks on your beautiful cladding.

Protect the end grain. The end grain of wood boards absorbs moisture at 10-12 times the rate of face grain. Seal all cut ends with a quality end-grain sealer or wax before installation. This single step can dramatically reduce checking, splitting, and rot at board ends.

Maintain ground clearance. Keep the bottom of your cladding at least 6-8 inches above grade to prevent splash-back and soil contact. A gravel strip around the base of the sauna helps with drainage and reduces splash.

Choosing the Right Cladding for Your Sauna Project

The right choice ultimately depends on your priorities. If you value a traditional, time-tested aesthetic and want a cost-effective option with good all-around performance, board and batten is hard to beat. If clean, contemporary lines are your style and you want a cladding profile that pairs well with modern sauna designs, shiplap is the natural choice. And if you want the ultimate in durability, minimal maintenance, and head-turning visual impact, shou sugi ban is in a league of its own.

Many custom sauna builders find that combining cladding styles can produce stunning results — for example, using shou sugi ban on the primary facade and shiplap on the sides, or pairing board and batten walls with a contrasting accent panel. If you're planning a custom sauna build, don't feel locked into a single profile. The best saunas often mix materials and textures to create a design that's uniquely personal.

Whether you're building from scratch with raw sauna lumber or choosing a pre-designed outdoor sauna kit that comes with the cladding integrated, understanding these three profiles puts you in a strong position to make the right decision for your space, your climate, and your style.

Frequently Asked Questions

Can I apply shou sugi ban to an existing outdoor sauna?

Yes. If your sauna's exterior boards are sound but weathered, you can remove them, char them, and reinstall. Alternatively, you can install new shou sugi ban boards over the existing cladding using furring strips to create a rain screen gap. This is a popular renovation approach for aging saunas that need both a cosmetic refresh and improved weather protection.

Is shiplap or board and batten better for a DIY sauna build?

Board and batten is generally easier for DIY builders because it doesn't require precision-milled rabbet joints. You can use standard flat boards and add battens over the seams. Shiplap requires properly milled boards (or a table saw with a dado blade) to cut the rabbet joints. If you're comfortable with basic woodworking, either is achievable. Explore the step-by-step building guides available in our learning center for more hands-on advice.

What's the best finish to apply over exterior sauna cladding?

For natural wood cladding (board and batten or shiplap), a high-quality penetrating oil finish is ideal. Products containing linseed oil or tung oil soak into the wood grain and provide UV protection and water repellency without forming a surface film that can peel or crack. Avoid film-forming finishes like polyurethane or varnish on exterior wood — they'll fail quickly under the thermal stress of a sauna wall. For shou sugi ban, a raw tung oil or pine tar finish is traditional and effective.

Do any pre-built outdoor saunas come with these cladding styles?

Many manufacturers integrate high-quality exterior cladding into their sauna designs. SaunaLife's cabin saunas feature spruce exterior cladding with clean horizontal profiles. Auroom saunas use thermally modified timber in sleek, modern profiles. True North's cabin and pod saunas offer cedar cladding with weather-resistant construction. If you'd rather not build from scratch, these ready-to-assemble options deliver professional-grade cladding without the complexity of a fully custom build.

How do I protect sauna cladding in extreme winter weather?

In harsh climates, focus on three things: proper roof overhang (at least 12-18 inches to protect the wall face from direct rain and snow), adequate ground clearance, and a well-vented rain screen behind the cladding. Ensure your sauna's roof has a drip edge and that snow can't pile up against the base of the walls. A sauna that's properly detailed at the roof, base, and openings will handle even the harshest winter conditions without issue, regardless of which cladding style you choose.