Outdoor Sauna Wood Treatment – All You Need to Know

view from an outdoor sauna

Does an outdoor sauna need wood treatment? Do you need to apply wood stain or wood sealant to an outdoor sauna? Yes, an outdoor sauna should be treated with a wood sealant to enhance its durability and protect it from moisture, UV, mold, and insect damage. Below we cover everything you need to know about outdoor sauna wood treatment.

Should You Treat the Exterior of an Outdoor Sauna?

Should the exterior of an outdoor sauna be treated with a wood sealant or wood stain? The answer to this question depends on the type of wood used to make the sauna. Most outdoor saunas are made from cedar or thermowood. These woods are weather-resistant and adding wood treatment is optional.

outdoor sauna in the snow

However, here at Home Sauna Heaven, we recommend you add wood treatment regardless of the type of wood your sauna is made from. Other types of wood such as pine and spruce are more susceptible to weather damage and require a protective coat of wood treatment.

Either way, if you want to protect your outdoor sauna and ensure it’s in good working order for many years – you should treat the wood with a wood stain or sealant material. This will not only keep your sauna looking great, but it will also help protect it from water, UV, insect, and mold damage. And, never apply wood stain or sealant to the interior of a sauna cabin – see below.

How to Apply Wood Treatment to an Outdoor Sauna

Once you’ve decided to apply wood treatment for your outdoor sauna the next question is which one to apply. Our advice is to get the best quality sealant or wood stain you can get your hands on. A high-quality wood treatment will last longer and protect your sauna better. And, it takes the same length of time to apply a low-quality wood treatment as a high-quality one.

outdoor sauna in a garden

All sauna wood treatment products have a color tint. This characteristic imparts UV protection to the stain. And, once applied will lift the color of your sauna and delay its discoloration. So, choose a treatment with a color tint you find appealing. Reddish browns and golden yellows are among the most popular.

Applying the treatment is a simple process. Take a look at the directions on the side of the tin for specific instructions and refer to the steps below for general guidelines.

Clean the Exterior

Begin by cleaning the sauna exterior. Ensure the surface is dust and dirt free. Use a mild detergent as necessary and allow to completely air dry before proceeding to the next step.

Sand Uneven Sections

If you notice any sections have uneven or rough edges you can gently sand them to create a smooth surface. This will also help the wood treatment adhere to the timber surface.

Apply the Wood Treatment

Apply the treatment following the manufacturer’s guidelines. Using a brush works well for ensuring all wood panels receive an equal coat. Pay attention to the number of coats you need to apply and the time you must allow between coats for the wood sealant to dry.

Apply Additional Coats

Once the first coat has dried and you can proceed with additional coats if necessary. Most sauna wood treatments require at least two coats to create a water-tight and UV-resistant seal.

How Often Should You Add Wood Treatment?

If you choose to add wood treatment to your sauna – we recommend you reapply it every year. This will ensure you are keeping your sauna in tip-top shape and doing all you can to protect it from UV and weather damage.

outdoor wooden sauna

If you are adding a wood sealant to your sauna take a look at the tin it comes in. The manufacturer will include guidelines on how often you need to reapply. The frequency will be influenced by several factors including the type of wood treatment used, the amount of rainfall experienced in your area, and the level of UV sunlight exposure.

However, as a general rule of thumb, we recommend you add wood treatment annually. Bear in mind, most wood stains and sealants require two coats to complete the process. The process will take several hours to complete. And, you’ll have to wait for the first coat to dry before adding the second.

What About the Inside of the Sauna?

Never apply wood stain or sealant to the interior of a sauna. Wood treatments contain volatile chemicals that off-gas when heated. And, this is something you definitely don’t want happening inside your sauna cabin.

woman standing inside a sauna with a glass door and temperature gauges on the wall

The volatile chemicals contained in many wood treatments are released in gaseous form when they are heated up. If this occurs when you’re sitting inside enjoying a sweat session you will inhale the chemicals while you relax. This can make you feel unwell and lead to several health issues such as feeling dizzy and nauseous.

If you want to treat the wood in the sauna interior you’ll need to use a special type of wood preservative designed specifically for this purpose. These special wood preservatives are water-based materials and contain zero volatile chemicals. They will not release gaseous chemicals as they are heated.


What Is Thermowood?

Thermowood is a type of wood that has been treated to increase its durability and resistance to weather damage. It is an excellent choice for outdoor saunas as it stands up well to the elements and is resistant to moisture damage.

woman sleeping on a western red cedar sauna bench

Thermowood is manufactured by modifying wood using a heat treatment process. The procedure involves subjecting the wood to very high temperatures of 320-410°F in the absence of oxygen. This triggers a structural and chemical change in the wood that increases its durability, and stability, and boosts its resistance to rot and insect damage.

It is a superbly durable wood for outdoor furniture such as saunas, decking, and fences. It is a sustainable material and is made using a renewable resource – timber. Although it is resistant to outdoor elements you should still apply a protective coat of wood treatment to further enhance its durability and expected lifespan.


About the Author


• Sauna Specialist

Meet Jake, a man with a passion for sauna therapy. Jake’s background is in science. And, his passion is wellness and basketball. Growing up in Orlando Florida, Jake enrolled in Florida International University where he graduated with a BS in Biological Sciences.

As a young man, he worked in the spa and wellness center at the renowned Breakers Palm Beach luxury hotel. Here he developed his skills and understanding of client-centered wellness delivery. Upon graduating from FIU he took up a research position focusing on the application and practical effects of steam therapy.

His research has contributed to advancing the understanding of steam sauna therapy and how it can be applied in the occupational health environment. His work in this area has been officially recognized for its impact on the field.

Jake is a devoted fan of the Orlando Magic basketball team. When not working and advancing his research he enjoys attending games at the Kia Center in downtown Orlando. He also likes to remain active in his local sports community and volunteers as a basketball coach for his local youth team.

With his background in scientific research and passion for wellness, Jake is a valuable addition to the Home Sauna Heaven writer’s team where he shares his knowledge and understanding of sauna therapy, steam sauna therapy, and how they can be used for best effect.

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