Learn About The Wood We Use
Canadian Red Cedar
Our specially sourced Canadian red cedar is a premium, naturally durable softwood that has been used traditionally for saunas and outdoor structures. We use a clear, top grade cedar that is modern, uniform and ages beautifully. It starts as a warm reddish color then becomes silver gray as it ages. Cedar has that distinctive aroma, and natural resistance to insects and decay due to its inherent oils. Cedar also offers excellent insulation properties, making it especially well-suited for sauna interiors and colder climates. However, it comes at a significantly higher cost, particularly for the clear-grade lumber we use. We recommend finishing it on site to give it a boost of extra protection once a year.
Thermowood
Thermowood is a sustainably modified softwood that has been heat-treated at very high temperatures (typically 180–220°C) using only heat and steam—no chemicals.
It is the strongest and most durable wood for outdoor use. It has a little more wood grain visible than clear cedar and can look either very modern or rustic depending on the finish. We are happy to recommend and do test panels to ensure you get the finish and look you want.
Thermowood performs exceptionally well in harsh outdoor environments, especially in high UV and rainy climates where untreated wood would typically degrade more quickly. Over time, it weathers into a uniform silvery-gray patina if left untreated, and it requires minimal maintenance compared to many traditional exterior woods. A low maintenance finish can help stretch this wood’s durability and beauty for even longer. It has somewhat lower insulating properties and may require extra insulation for the coldest winter climates.
Finnish Pine
Finnish Pine is a softwood that is less expensive than the other woods we use. We typically leverage it as an insulating in-between-layer for our walls and it is not visible. It can also be used well inside a sauna as a cost-saving measure for people who are on a tight budget. It does not have the aroma of cedar or the strength of thermowood, but it can get the job done nicely. This is a reasonable choice for a small backyard sauna on a budget.
Hemlock
Hemlock is a clean, light-toned softwood that is commonly used in sauna construction. It has a smooth, uniform grain with very few knots, giving it a more modern and refined appearance compared to more rustic woods. Unlike cedar, hemlock is non-aromatic, which makes it a great option for those who prefer a neutral scent or have sensitivities to strong wood oils. It is stable and resists warping in the controlled environment of a sauna, but it does not have the same natural resistance to moisture, rot, or insects as red cedar or Thermowood, which is why we typically only use it for the inside of our designs upon request. We do not recommend hemlock as an exterior wood as it degrades much faster in weather and is a bit more expensive than thermowood.
Birch
We use a finished birch plywood as a substitute for the much more costly drywall material / process to finish the walls, floors and ceiling in our outdoor rooms. It has a light color and a smooth, consistent grain that creates a clean, bright aesthetic. It looks modern and can be stained or left natural. It does not hold heat well which means it naturally keeps a room a bit cooler feeling on hot days.
The Best Zero-VOC Outdoor Wood Finishes for Cedar - Exterior
Best For: Maintaining a natural, rich wood look.
Highlights: A 100% sustainable, petroleum-free oil finish made with Brazilian rosewood oil. It has zero VOCs, provides 99% UV protection, and can be applied quickly with a brush or sprayer—you simply apply it, let it penetrate for 10–20 minutes, and wipe off the excess. [1]
Eco Wood Treatment Exterior Wood Stain & Preservative
Best For: A permanent, "one-and-done" application.
Highlights: A mineral-based powder concentrate that you mix with water and apply just once. It is completely VOC-free, safe for garden beds, and never flakes or peels. It reacts with the cedar fibers to permanently prevent rot while accelerating a gorgeous, silver-gray weathered look. [1, 2]
TimberSoy Fence Stain & Sealer Factory Tinted cedar - semi-transparent 1 gal Eco Safety Products
Best For: Locking in color without a chemical smell.
Highlights: A bio-based, plant-oil derived stain and sealer that features 0 grams/liter of VOCs. It is incredibly easy to apply, penetrates deeply to waterproof the wood, and dries in under an hour
The Best Zero-VOC Natural Wood Oil - Sauna Interiors
Sauna Shield Sauna Wood Oil: A pure, toxin-free, and fragrance-free paraffin oil engineered specifically for sauna environments. It prevents moisture absorption, cracking, and staining without emitting a single scent.
SaunaLife Odorless Sauna Paraffin Wood Oil: Specially formulated to be fragrance-free so you can enjoy the native, therapeutic scent of the red cedar without competing chemical aromas.
Specialized Water-Based Sauna Sealants (Best for Walls & Ceilings)
Clearlight Sauna No-VOC Varnish: An entirely odor-free, zero-VOC interior water-based barrier used by luxury infrared sauna manufacturers. It protects against stains and moisture for up to five years without any off-gassing when the sauna heats up
Northern Lights Group Sauna Sealant: A highly effective, low-odor, non-toxic water-based interior sealer. It blocks steam and humidity from warping or splitting the cedar panels while remaining safe for high-heat spaces
To calculate exactly how much oil or sealant you need, you must find the total square footage of the wood surfaces and divide it by the product’s coverage rate.
Because your exterior and interior products will be different (e.g., an exterior oil vs. an interior paraffin oil), you need to calculate their areas separately and know if the product needs more than one coat applied.