The Roots collection transforms a wood side stream into premium sauna panels by using the knotty sections of Finnish aspen trunks that arise naturally during knot-free production. Rather than treating these character-rich offcuts as inferior material, we at Pieksäwood have built an entire product family around them, celebrating their natural grain patterns and knot details as design features rather than defects.
This approach combines circular economy thinking with over 75 years of Finnish woodworking expertise, producing panels that are both visually distinctive and genuinely sustainable. The sections below answer the most common questions builders, designers, and sauna enthusiasts ask about Roots panels and the materials behind them.
What makes a wood side stream suitable for premium sauna panels?
A wood side stream is suitable for premium sauna panels when the material retains the structural integrity, moisture resistance, and thermal properties required for sauna conditions, even though it was separated from the main production flow for aesthetic reasons. In the case of Finnish aspen, the knotty trunk sections that emerge alongside knot-free premium cuts are structurally sound and perform exceptionally well in heat and humidity.
The key distinction is between a defect that compromises performance and a characteristic that simply differs from a uniform appearance standard. Knots in aspen do not weaken the panel in sauna applications the way resin-filled knots in pine can. Aspen is naturally resin-free, so its knot zones remain stable, smooth to the touch, and safe at high temperatures.
What elevates a side stream to premium status is the combination of responsible sourcing, skilled processing, and intentional design thinking. We saw that these knotty aspen sections told a richer visual story than their knot-free counterparts, with unique grain swirls and natural markings that make every panel one of a kind. By investing in careful sawing, thermal modification where required, and hand-planing, we turn what was previously underutilised material into a product with genuine design value.
How does thermal modification transform raw aspen into sauna-grade material?
Thermal modification transforms raw aspen into sauna-grade material by heating the wood to high temperatures using only hot air and steam, with no chemicals involved. This process permanently alters the wood’s cell structure, reducing its ability to absorb and release moisture, increasing its dimensional stability, and deepening its colour to a warm, rich brown.
For sauna use, these changes are highly relevant. A sauna environment cycles repeatedly between intense heat, steam, and cooling. Untreated wood expands and contracts with each cycle, which over time can cause warping, cracking, or surface roughness. Thermally modified aspen resists these movements far more effectively, maintaining its shape and smooth surface through years of regular use.
The colour transformation is equally important from a design perspective. Natural aspen is a pale, harmonious timber with a clean, light appearance. After thermal modification, it takes on a consistent warm brown tone that complements both traditional and contemporary sauna interiors. Because the colour change runs through the full depth of the wood rather than sitting on the surface as a stain would, it does not fade or peel over time.
We carry out all thermal modification at our own modern facility in Pieksämäki, using Finnish wood products from our own sawmill. This means every step of the process, from log to finished panel, is controlled under one roof in Finland, ensuring consistent quality throughout the Roots collection.
What is the Roots story behind Pieksäwood’s sauna panels?
The Roots story began in 2024 when we launched our own Finnish aspen sawmill operation in Pieksämäki. As we sawed aspen logs for our knot-free premium range, the knotty sections of each trunk emerged as a natural byproduct. Instead of treating these as waste or secondary material, we recognised their visual character and built a dedicated product family around them.
The name Roots reflects both the literal origin of the material, the inner trunk sections closest to the tree’s branching points, and the deeper idea of connecting back to the Finnish forest. Every Roots panel carries the individual markings of the tree it came from: grain patterns shaped by decades of growth, knot details that record where branches once reached toward the light, and a surface texture that no manufactured material can replicate.
The collection includes panels, posts, and interior elements available in both natural aspen and thermally modified aspen. All products are manufactured entirely in Pieksämäki, from sawing through thermal modification to hand-planing and packing. By using every part of the aspen logs we process, we ensure nothing is wasted, and we create something genuinely beautiful from material that was previously undervalued.
Roots is also a statement about what sustainable production can look like in practice. Circular economy principles are not an abstract concept here; they are built directly into the product’s origin story.
How does thermally modified aspen compare to alder and radiata pine for saunas?
Thermally modified aspen, alder, and radiata pine each have distinct characteristics for sauna use. Thermally modified aspen offers superior dimensional stability and a rich natural colour without chemical treatment. Alder provides a naturally warm tone and excellent heat tolerance in its untreated form. Radiata pine, when thermally modified, becomes a cost-accessible alternative, though it lacks the resin-free purity of aspen and alder.
Thermally modified aspen vs. alder
Both aspen and alder are resin-free and pitch-free, which makes them the two most recommended species for sauna benches and panels. Neither species becomes uncomfortably hot to the touch even in intense heat, and both have smooth, pleasant surfaces that feel good against skin. Alder has a naturally warmer, slightly reddish tone and is often chosen for traditional sauna aesthetics. Thermally modified aspen, by contrast, offers a deeper brown that suits contemporary interior styles, along with enhanced moisture resistance that extends the panel’s lifespan in high-humidity conditions.
Thermally modified aspen vs. radiata pine
Radiata pine in its natural state is not well suited to sauna environments because of its resin content, which can bleed to the surface under heat and cause discomfort or staining. Thermal modification largely addresses this by breaking down the resin compounds, making thermally modified radiata pine a viable sauna material. However, it does not match the inherent resin-free quality of aspen or alder, and the grain character is quite different. We include thermally modified radiata pine in our range for customers who prefer its appearance or price point, but for the most demanding sauna applications, thermally modified aspen remains the stronger choice.
Why is Finnish aspen considered the best wood for sauna panels?
Finnish aspen is considered the best wood for sauna panels because it is naturally resin-free, pitch-free, and extremely smooth, making it safe and comfortable even at high sauna temperatures. It does not release sticky compounds or splinters when heated, and its low thermal conductivity means the surface stays comfortable to the touch even when the air temperature is intense.
Beyond safety and comfort, Finnish aspen has a fine, even grain structure that responds exceptionally well to planing, producing a surface quality that is difficult to achieve with coarser-grained species. This makes it ideal for both bench surfaces and wall panels where tactile quality matters as much as visual appearance.
The Finnish climate also plays a role. Aspen grown in Finland develops slowly due to the northern growing season, which produces denser, more uniform timber than faster-grown equivalents from warmer regions. This slower growth contributes to the wood’s stability and its ability to handle repeated cycles of heat and moisture without degrading.
For the Roots collection specifically, Finnish aspen sourced from our own sawmill in Pieksämäki carries full traceability from forest to finished product. Customers can be confident that the material is responsibly produced and that the entire manufacturing chain remains in Finland.
Where can builders and designers source Roots sauna panels?
Builders, designers, and sauna professionals can source Roots sauna panels directly from us at Pieksäwood. We supply both B2B and B2C customers, including hardware and timber retailers, sauna manufacturers, construction companies, architects, and private customers renovating homes or summer cottages.
Because we control the full production chain in Pieksämäki, from sawing and thermal modification to planing and packing, we are well positioned to handle both standard orders and custom specifications. If a project requires specific dimensions, surface treatments, or a combination of natural and thermally modified aspen, we can accommodate those needs with the flexibility that comes from in-house manufacturing.
For architects and interior designers working on public spaces or commercial sauna facilities, Roots panels offer a material story that adds genuine value to a project brief: fully Finnish, circular economy origin, hand-finished, and visually distinctive. Our team provides fast, personal service and can advise on the right product specification for each application.
To explore the Roots collection or discuss a specific project requirement, reaching out to our team directly is the most efficient route. We respond quickly and work closely with each customer to ensure the right product reaches the right project.
