When you walk into a sauna, it's like being wrapped in the warmth, the aroma has a calming and relaxing effect on your body and mind. The best part of having a sauna is that you can experience these benefits to the maximum extent possible. The way you experience the sauna will be entirely determined by one important factor, which is the type of wood used. When selecting wood for your sauna there are more things to consider than just what the wood looks like; the type of wood you choose will determine how well your sauna performs, how long it lasts, and how enjoyable your experience will be. The conditions inside the sauna are very extreme with very high temperatures (150F - 190F or 65C - 90C) and quickly changing humidity levels. Not every type of wood is capable of handling the abuse of such an extreme environment without warping, cracking, or becoming the perfect habitat for mold growth. The type of wood you choose has a direct impact on how the sauna will feel when heated, the aroma in the air, and the overall atmosphere you will create for yourself and others while using the sauna. In "How to Choose the Best Wood for Your Home Sauna: An In-Depth Guide on Selecting the Best Wood Type" we'll help guide you through this critical decision-making process. We'll provide you with insight into what thermal resistance, moisture management, and structural integrity means in regards to wood types. This will allow you to make an educated decision when selecting the right wood type that will result in your home sauna being a durable, safe and completely relaxing destination for years to come.
The sauna's interior is one of the toughest environments for any construction material. Not only will temperatures typically range between 150 to above 190 degrees Fahrenheit, but the humidity levels can also spike dramatically during the 'löyly' process where water is poured on to hot stones.The intense dry heat of a sauna combined with a sudden influx of steam represents a tremendous amount of thermal stress and moisture exposure to the wood. When choosing the right type of wood for your sauna, it is essential to select one for its low thermal conductivity, meaning the wood does not absorb or conduct heat quickly. Woods with high thermal conductivities will become so hot that they become too uncomfortable and potentially dangerous to lean against, sit upon, or otherwise use in the sauna. The optimal sauna wood will provide insulation from the heat contained within the sauna while remaining cool enough to touch your body comfortably. The wood used in your sauna must also resist moisture absorption, so it does not swell or warp and ultimately develop mold or mildew that can be harmful to health.
Key Properties of Ideal Sauna Woods
Wood types should be evaluated based on several key properties, which should be considered non-negotiable when selecting wood for saunas. The first property to consider when evaluating wood types is their density and dimensional stability. For example, wood types that expand and shrink the least with changes in humidity and temperature are generally the best wood choices. Cedar and hemlock are examples of wood species with excellent dimensional stability.
The second property to consider is the amount of resins and oils that are naturally contained in the wood. A certain amount of natural oils in wood is good for providing aroma and providing moisture resistance, but an excessive amount of sap or resin could cause major problems. When wood is subjected to high temperatures, many of the resins contained within the wood may become sticky and release strong, overpowering odors or seep from the wood, creating a very messy and hazardous situation. Excellent examples of wood species that have a more neutral balance of resins and oils, and also perform well in a sauna environment, are clear, kiln-dried Western Red Cedar or Nordic Spruce.The natural insect and decay resistance of these woods reduces the amount of chemical treatment necessary to prevent them from breaking down, which reduces the amount of chemicals that off-gas into the hot air of the sauna.
Top Wood Choices for Sauna Interiors: A Detailed Comparison
Western Red Cedar: Western red cedar is widely regarded as one of the best woods to use for sauna interiors because of its remarkable characteristics. A very low density rate makes cedar one of the best insulating materials available, as cedar is very cool to the touch. Western red cedar contains naturally occurring thujaplicins that are effective at killing fungus and insects, which gives it a higher level of resistance to decay. The unique reddish color of Western red cedar and its pleasant light, sweet scent also contribute significantly to the overall sensory experience of being in a sauna. However, with these superior qualities come a higher price.
Nordic Spruce (sometimes referred to as Scandinavian or Baltic Whitewood): There is a reason Nordic spruce is the traditional wood used in Finnish saunas for hundreds of years. This slow-growing wood has a fine, dense grain and is both incredibly strong and stable due to the extreme conditions found in the cool climates of the Nordic region. The light, almost-white color of Nordic spruce reflects light, resulting in a wonderfully bright sauna interior, and it has a very subtle smell that makes it ideal for a sauna environment. Although its lack of aroma does not lend itself to the same sensory experience as cedar, Nordic spruce provides a definitive and classic sauna experience. Nordic spruce has phenomenal thermal performance, and its cost is less than that of the more expensive ceder.
Hemlock: Hemlock is an economically-sound alternative to the two previously mentioned woods. Known for its strength, stability, and smooth, knot-free appearance, Hemlock is a light-colored wood, similar in shade to spruce, and has a neutral, non-aromatic scent, making it an excellent choice for those who may have sensitivities to the stronger aromatic scents found in cedar wood. Hemlock also has good moisture resistance due to its wood fibre structure and low thermal conductivity, which makes it ideal for use in a sauna.One of the key factors contributing to the wide use of spruce and fir for building sauna kits is their price. They are both widely used because of their consistency in texture and price points.
Woods to Avoid in Your Home Sauna
Many woods that should be avoided when building a sauna include all pressure-treated woods, because the chemical preservatives (i.e. copper and arsenic) used in pressure-treating can vaporize when heated to high temperatures and release harmful toxins into the enclosed space. Also avoid the use of resinous softwoods such as standard pine and some varieties of fir, as they can produce sticky sap that bleeds out when heated due to their high sap content. This sap can get all over and result in minor burns if touched, and many people also dislike the strong and sometimes turpentine-like smell that accompanies heated pine sap.Hardwoods such as Oak or Maple don't work out well in sauna applications, also their very good thermal conductivity means that they get hot to the touch and crack under the dry heat cycles that exist in an elevated sauna environment.
Practical Considerations: Grain, Knots, and Installation
After you've chosen your wood species, you will need to pay attention to details with the lumber you select. It is best to choose clear/select grade vertical grain boards for your walls and ceiling panels. Vertical grain boards (quarter-sawn) expand and contract less than flat-sawn boards, which reduces the likelihood of warping. Vertical grain boards also provide a more uniform, aesthetically pleasing linear grain pattern.
Knot handling is of utmost importance. Small, tight knots are generally accepted, however, large, loose, or "fall-out" knots should be avoided on benches as they may become uncomfortable hot spots or may fall out and leave a hole. All wood should be kiln-dried to an appropriate moisture content (generally below 10%) to provide stability from day one. When you install, you should use stainless steel or other non-corrosive fasteners as regular steel will corrode quickly in a sauna and will create unsightly stains on the wood. You should also leave space between your boards so that they can naturally expand and contract due to the changing temperature in the sauna.
By selecting the right wood to build your home sauna carefully, your home sauna experience can be built on a foundation of safety and comfort. When you select wood, look for characteristics such as low thermal conductivity, high dimensional stability, and resistance to nature's elements. By focusing on these performance factors, Western Red Cedar, Nordic Spruce, and Hemlock will be the most likely choices to perform well in this application. At the same time, there are woods to avoid, as these types of wood are unsafe and not comfortable to sit on. Additionally, choosing the right wood will be the structure of your wellness retreat. In order for your wood to produce a peaceful space that smells wonderful and has a long life, it is important to consider the above factors in your selection.
