The core of high-quality saunas lies in the bench structures, which are in constant contact with your body. Heat-treated aspen has risen among the most popular bench materials due to its excellent durability, comfort, and beautiful appearance. It makes the sauna experience even more pleasant and long-lasting. In this article, we will go through the most important benefits of heat-treated aspen in sauna bench structures, its durability, and provide practical tips for making the right material choices.
What makes heat-treated aspen a special sauna material?
Heat treatment is a natural process that significantly changes the properties of wood. In the treatment, lumber is first dried completely by rapidly raising its temperature to 100 degrees. When the wood is dry, the temperature is slowly raised to 175-210 degrees for 1.5-3 days depending on the wood species, thickness, and desired color shade.
Heat treatment is regulated with steam and hot air. Steam acts as protection preventing the wood from cracking and igniting, and affects the chemical changes occurring in the wood. During the process, water and resin are removed from the wood, which thoroughly changes the wood’s structure.
For aspen, heat treatment makes a special change. Naturally light aspen is thoroughly colored during treatment into an elegant brown. At the same time, its moisture movement decreases significantly and biological durability improves. These changes make aspen an ideal material for saunas, where conditions constantly vary from dry to moist and from cool to hot.
The most important benefits of heat-treated aspen in sauna bench structures
Heat-treated aspen offers several significant advantages that make it an excellent choice for sauna bench structures:
- Low thermal conductivity – Thanks to heat treatment, wood conducts heat significantly less, which makes benches feel pleasant even in a hot sauna. You won’t feel uncomfortable heat when sitting on the benches.
- Resin-free – The treatment process completely removes resin from the wood, so the bench surface remains pleasant and doesn’t become sticky in heat.
- Durability – Heat treatment improves the biological durability of wood, which extends the lifespan of bench structures.
- Lightness – Aspen is naturally a light wood species, which makes installing and possibly moving bench structures easier.
- Aesthetic appearance – Treatment gives aspen a beautiful, warm brown shade that brings a luxurious atmosphere to the sauna.
- Pleasant scent – After heat treatment, aspen gets a pleasant, natural wood scent.
Additionally, heat-treated aspen is a completely non-toxic and ecological choice, as the treatment uses only heat and steam – no chemicals or toxins at all.
Durability in high temperatures and humidity
A sauna is an extremely demanding environment for materials. Temperature can vary considerably, and humidity constantly changes from dry to very moist. Ordinary untreated wood reacts strongly to these changes by expanding and contracting, which over time leads to cracking and warping.
Heat-treated aspen maintains its dimensions and shape significantly better. During treatment, the wood’s cellular structure changes permanently, which reduces its moisture movement by as much as 40-50%. This means that bench structures stay straight and tight for a long time.
Heat treatment also improves the wood’s rot resistance. During treatment, the wood’s hemicelluloses partially decompose, which makes the wood less attractive to microbes and fungi. This means in practice a longer lifespan for bench structures, especially in the sauna’s moist conditions.
Dimensional stability and improved durability also mean less maintenance need over time. Heat-treated aspen is the most durable wood option for saunas, and doesn’t require special surface treatments or protective agents to maintain its properties in the sauna environment.
How does heat-treated aspen compare to other bench materials?
Several different wood species are used as sauna bench materials, the most common being aspen, alder, abachi, and spruce. Let’s compare the properties of these to heat-treated aspen:
- Untreated aspen – Natural aspen is already a good bench material due to its light color and low thermal conductivity. However, heat treatment significantly improves its durability and dimensional stability.
- Alder – Beautiful red alder is a traditional choice for saunas. Compared to heat-treated aspen, however, it conducts slightly more heat, which can make benches feel hotter.
- Abachi – African abachi is also a popular option due to its low thermal conductivity. However, heat-treated aspen is a domestic and more ecological choice with similar properties.
- Spruce – A more affordable option, but spruce easily becomes resinous and darkens over time. Heat-treated aspen maintains its appearance better and is more pleasant to touch.
Heat-treated aspen combines the best aspects of many different materials: it feels pleasant against the skin, is durable in the sauna’s varying conditions, aesthetically beautiful, and completely non-toxic as well as being a domestic material.
Practical perspectives for bench structure design
When designing a sauna from heat-treated aspen, it’s good to consider a few practical things:
- Bench board direction and air gap – Install bench boards so that there’s a small air gap between them (5-7 mm). This allows air circulation and water drainage, which extends the lifespan of bench structures.
- Fastening – Use fasteners made of stainless steel that withstand the sauna’s moist conditions. Ensure that fasteners are embedded deep enough for comfort.
- Cleaning – Heat-treated aspen is easy to keep clean. After sauna use, it’s enough to rinse the bench structures with clean water and leave them to dry. This keeps the bench surface hygienic.
- Thickness – The recommended thickness for bench boards is at least 28 mm, so they withstand weight well and maintain their shape for a long time.
- Surface treatment – Heat-treated aspen doesn’t require separate surface treatment, but if desired, you can treat bench surfaces with paraffin oil intended for sauna use. This enhances the wood’s beautiful shade and makes cleaning easier.
In the design phase, it’s also worth considering the ergonomics of bench structures. In a properly designed sauna, sitting height, backrest angle, and footrest placement are all important factors that affect the comfort of the sauna experience.
In sauna design, you can take advantage of heat-treated aspen’s versatility: the same material can be used in benches, wall panels, and decorative strips to create a unified appearance.
We at Pieksäwood have specialized in heat-treated aspen and other high-quality sauna wood products for over 20 years. We manufacture all our products carefully in Pieksämäki, Finland, and offer expert help with sauna material choices. Explore our previous sauna implementations and get inspired by bench structures made from heat-treated aspen that bring durable quality and timeless elegance to your sauna for years to come. For professional guidance on your sauna project, please contact our sauna experts.