When choosing an outdoor sauna, the visible design is only part of the decision. Behind the glazing, benches and exterior finish is the structure itself - the material that determines how the sauna is built, how its surfaces look and how the different elements come together.

DEIZ outdoor saunas are built around Cross-Laminated Timber, or CLT. But the DEIZ approach goes beyond simply using standard construction CLT. We produce our own CLT panels specifically for sauna construction, where the timber is intended to serve not only as a structural element but also as a visible finished surface.

This distinction is important. Conventional CLT is primarily developed as a construction material. In a DEIZ sauna, the panel also plays an architectural role: it defines the interior, influences the exterior appearance and becomes one of the main visual characteristics of the finished sauna.

So what exactly makes the DEIZ CLT panel different?

What is Cross-Laminated Timber?

CLT stands for Cross-Laminated Timber.

A CLT panel is made from multiple layers of timber arranged so that the direction of the wood alternates between neighbouring layers. This cross-laminated structure creates a solid, rigid panel with good geometric stability.

Instead of building a sauna wall from a lightweight frame and then covering that frame with separate interior and exterior layers, CLT allows the wall itself to become a substantial timber element.

This creates a fundamentally different construction concept.

A typical frame sauna may include:

• structural framing;
• insulation;
• membranes;
• interior cladding;
• exterior cladding.

A CLT sauna can use the massive timber panel itself as the main structural wall and, depending on the design, as part of the visible interior or exterior surface.

For DEIZ, this relationship between structure and visible material is one of the central ideas behind the product.

Not all CLT is developed for the same purpose

CLT is widely used in modern timber construction, including houses, commercial buildings and larger structural projects.

In many of these applications, the panel is selected primarily for structural performance. Its visible appearance may be secondary because the CLT can later be covered with insulation, plasterboard, façade materials or another finish.

A sauna creates a different requirement.

Here, the timber may remain visible only a short distance from the user. You see the grain, the joints, the lamellas and the transition between different surfaces every time you enter the room.

For this reason, DEIZ develops its panels around two requirements:

1. the panel must function as part of the sauna structure;
2. the visible timber surface must form part of the final architectural expression.

The goal is not simply to build with CLT. The goal is to make CLT appropriate for a finished outdoor sauna where the material remains visible.

DEIZ produces its own CLT panels

One of the main differences is that DEIZ does not simply select a standard building panel and design a sauna around it.

The panel itself is part of the product development process.

DEIZ produces CLT panels specifically for its sauna construction, allowing greater control over:

• lamella dimensions;
• visible timber selection;
• bonding;
• panel format;
• surface appearance;
• detailing between panels.

This gives the sauna and the material a closer relationship.

The dimensions, joints and surfaces are not treated as unrelated construction components. They are considered together as part of one finished product.

Additional bonding between the lamellas

A conventional CLT panel is created by bonding timber layers together.

Depending on the production method, individual lamellas within the same layer may not necessarily be bonded along their side edges.

The DEIZ panel concept adds another level of bonding: the panel is bonded not only between the cross-laminated layers but also between neighbouring lamellas.

Why does this matter?

The purpose is to create a panel that behaves and appears more like a continuous timber surface rather than a collection of separate boards.

For the client, the important result is visual:

• fewer obvious divisions between individual timber elements;
• a more continuous surface;
• a cleaner relationship between adjacent lamellas;
• a more architectural rather than cladded appearance.

It is important not to turn this feature into unsupported numerical strength claims. Without specific structural testing, DEIZ does not present the panel as “X times stronger” than standard CLT.

The safe and accurate point is that the additional bonding between lamellas is part of DEIZ's approach to creating a more monolithic panel and a cleaner visible surface.

Narrower lamellas create a different visual rhythm

Another distinctive feature of the DEIZ panel is the width of the visible lamellas.

Construction CLT can often use comparatively wide boards. DEIZ uses narrower lamellas of approximately 50 mm.

This may sound like a small detail, but the difference becomes obvious when the timber remains visible across an entire wall or ceiling.

Wide boards create a stronger repeating pattern.

Narrower lamellas create a finer visual rhythm and allow the surface to read more evenly across a large area.

For a sauna interior, where the wall itself may remain exposed rather than being covered with lining, this can significantly influence the character of the room.

The timber still looks natural, but the surface feels more controlled and deliberate.

Visible faces are selected with appearance in mind

Wood is naturally variable.

Every board has its own:

• grain;
• knots;
• colour;
• texture;
• tonal differences.

That variation is part of the material and should not be hidden.

However, there is a difference between natural variation and unnecessary visual interruption.

In standard structural timber production, finger-jointed sections may be used to create longer timber elements. This is completely normal from a construction perspective.

But when the panel is intended to remain exposed, finger joints can interrupt the grain and create sudden changes in tone or texture.

DEIZ therefore pays particular attention to the visible surfaces and aims to avoid unnecessary finger-joint interruptions where the timber forms the finished architectural surface.

The objective is not to make natural timber look artificial.

It is to allow the natural character of the wood to remain visible without unnecessary technical interruptions dominating the surface.

Structure and finish become one material

This is perhaps the most important difference to understand.

In many traditional sauna constructions, the structure is hidden.

You see the lining, but not the wall that actually carries the building.

In a DEIZ CLT sauna, the same material can perform both functions.

The panel can be:

the structural wall

and at the same time:

the visible wooden surface.

That creates a different relationship between engineering and design.

There is less visual separation between “construction” and “finish”.

Instead, the timber panel itself becomes the architecture.

This idea is fundamental to the DEIZ product. The panel is designed to work not only as a construction component but also as part of the finished interior and exterior.

Why this matters inside a sauna

A sauna is one of the few architectural spaces where the user sits very close to the materials.

The wall is not something you see from across a large room.

You sit next to it.

You touch it.

You see the grain under warm lighting.

You notice the joints.

You see how the timber meets the glass, benches and ceiling.

That makes material quality and detailing particularly important.

A visible CLT interior creates a different character from conventional narrow sauna lining.

Instead of many separate horizontal or vertical boards, the room can read as a series of larger timber planes.

The result is visually calmer and more connected to the structure of the sauna itself.

A more continuous exterior surface

The same principle applies outside.

Traditional timber façades usually use individual boards.

That creates a clear repeated rhythm:

board → joint → board → joint.

There is nothing inherently wrong with this approach, but it produces a particular visual language.

DEIZ aims for a different effect.

The exterior is intended to read as a more continuous architectural surface, with fewer visual interruptions and carefully treated joints between the main panels.

This helps the sauna feel closer to a small architectural building than to a conventional timber garden structure.

CLT sauna vs frame sauna

One of the easiest ways to understand the DEIZ concept is to compare the underlying construction.

Frame sauna

A conventional frame sauna typically relies on:

• a timber structural frame;
• insulation between the studs;
• membranes;
• interior sauna lining;
• exterior façade cladding.

The visible wood and the structural wall are normally separate systems.

CLT sauna

A CLT sauna is built around solid timber panels.

The panel itself forms the main structural shell, and in a DEIZ sauna the timber can remain visible as part of the final interior and exterior.

This reduces the visual distinction between structure and finish.

The result is not necessarily “better” in every possible situation — it is simply a different architectural and construction approach.

For clients who want a visually clean, solid timber object rather than a conventional framed garden sauna, that difference can be important.

CLT sauna vs barrel sauna

Barrel saunas use another completely different structural principle.

A barrel sauna is typically formed from individual timber boards tightened together to create a curved shell.

This produces the familiar rounded shape and traditional garden-sauna appearance.

A DEIZ CLT sauna uses panel construction instead.

That allows:

• straight walls;
• rectangular proportions;
• a visually flat roof;
• large panoramic glazing;
• longer architectural volumes;
• terraces and anterooms;
• flexible positioning of windows and doors.

The distinction is therefore not simply aesthetic.

The construction method itself leads to a different type of architecture. DEIZ's own comparison materials distinguish barrel construction, light frame construction and panel-based CLT as fundamentally different systems.

Why panoramic glass works naturally with the DEIZ concept

Large glazing is one of the defining elements of many DEIZ sauna configurations.

The rectangular CLT structure allows panoramic glass to be integrated into clean architectural openings.

The glass has several functions.

It brings natural light into the sauna.

It opens the interior toward the garden, lake, forest or landscape.

It makes compact sauna rooms feel more visually connected to their surroundings.

And it creates contrast between two materials:

solid natural timber and transparent glass.

This relationship is one of the reasons DEIZ is designed as more than a simple enclosed sauna room.

The view, privacy, light and relationship with the surrounding property all become part of the sauna experience.

The panel supports different layouts

Although the panel system is a central part of the product, DEIZ does not limit every project to one fixed configuration.

The standard sauna models provide practical starting points, but different requirements may call for different layouts.

Depending on the project, options can include:

• sauna only;
• sauna with terrace;
• sauna with anteroom;
• sauna with terrace and anteroom;
• shower area;
• additional glazing;
• different door positions;
• customized internal planning.

Windows, doors, heaters, colours and finishes can also be adapted where technically appropriate.

The CLT panel system therefore serves as a common construction language across different sauna configurations rather than defining one fixed shape.

Factory preparation matters

A panel is only one part of the finished product.

The final result also depends on:

• accurate cutting;
• panel alignment;
• window openings;
• joints;
• roofing;
• ventilation;
• benches;
• glazing;
• electrical preparation;
• finishing.

For this reason, DEIZ prepares critical elements in controlled production conditions before the sauna reaches the installation site.

When access allows, the sauna can be delivered as a fully assembled module.

This keeps a large part of the work inside the production environment and reduces the amount of assembly required on the property.

For sites with difficult access, the same CLT concept can also be prepared as a panelised DIY kit for on-site assembly.

What about natural movement and cracks?

Wood remains a natural material regardless of how carefully it is engineered.

It responds to:

• temperature;
• moisture;
• sunlight;
• seasonal changes.

Small surface changes or micro-cracks can therefore occur over time.

DEIZ does not claim that natural timber will never change.

The purpose of the panel design, bonding and detailing is not to turn wood into an artificial material.

It is to create a well-controlled timber product while preserving the natural material itself.

This distinction is important when comparing genuine timber construction with synthetic or fully covered surfaces.

Natural variation should be expected and understood as part of the material.

What about exterior colours?

The appearance of the CLT façade can also be adapted through exterior finishes and colours.

However, colour is not purely an aesthetic decision.

Very dark colours absorb more solar heat than lighter colours. On timber surfaces, higher temperatures can increase drying and contribute to more visible changes in the material over time.

For this reason, lighter and medium façade tones can be a more stable choice when long-term visual consistency is the priority.

DEIZ can work with different colour directions, but very dark façades should be selected with an understanding of how natural timber reacts to sunlight and temperature.

Why DEIZ does not hide the timber

Many construction systems are designed to disappear behind the final finish.

DEIZ takes the opposite approach.

The timber itself is intended to remain part of the experience.

Inside the sauna, the visible CLT surface creates warmth and material continuity.

Outside, the clean panel geometry supports a restrained architectural form.

The purpose is not decoration for its own sake.

It is to let the material, structure and architecture work together.

What should you look at when comparing CLT saunas?

If you are comparing different CLT sauna manufacturers, the word “CLT” alone does not tell the whole story.

Ask:

Is the CLT intended to remain visible?

Some panels are developed mainly for structural use and are later covered.

How wide are the visible lamellas?

The dimensions of the timber elements influence the visual rhythm of the finished wall.

Are the visible surfaces selected specifically for appearance?

If the panel will remain exposed, surface selection matters.

How are the lamellas bonded?

Panel production methods differ.

How are panel joints detailed?

The quality of the joints strongly affects whether the building reads as one architectural object or a series of separate panels.

Is the sauna prepared in a factory or assembled completely on site?

Factory preparation can influence consistency and the amount of site work required.

Can the manufacturer adapt the layout?

A good panel system should support the needs of the project rather than force every client into one fixed configuration.

These questions reveal much more about the product than simply asking:

“Is this sauna made from CLT?”

The DEIZ approach in simple terms

The difference can be summarized in a few points.

Own CLT panel production
DEIZ develops panels specifically for sauna construction and visible timber surfaces.

Additional bonding between lamellas
The panel concept includes bonding both between layers and between neighbouring lamellas.

Narrower visible lamellas
Approximately 50 mm lamellas create a finer and more controlled visual rhythm.

Carefully selected visible faces
The timber is considered as part of the finished architecture rather than only as hidden construction material.

Structure and finish combined
The same timber panel can function as the structural shell and as a visible surface.

Architectural panel construction
The system supports rectangular volumes, large glazing and flexible sauna layouts.

Why the panel matters when choosing an outdoor sauna

When people first compare outdoor saunas, they often look at size, price, heater and photographs.

Those things matter.

But the structural system deserves equal attention because it determines much of what the sauna ultimately becomes.

A barrel sauna, lightweight frame sauna and CLT sauna can all provide heat and a place to relax.

They are nevertheless fundamentally different products.

The DEIZ approach is intended for clients who value:

• solid timber construction;
• visible natural material;
• clean architectural geometry;
• large glazing;
• considered detailing;
• adaptable layouts;
• factory preparation.

The CLT panel is the foundation that allows those elements to work together.

A CLT panel developed as part of the sauna itself

For DEIZ, CLT is not simply a construction material selected from a catalogue.

The panel is part of the product.

Its dimensions, bonding, visible surface, joints and relationship with glass and other components influence the entire architecture of the sauna.

That is ultimately what makes the DEIZ CLT panel different:

it is developed not only to build the sauna, but to remain visible as part of the finished sauna.