How To Remove Mold In Sauna And Stop It From Coming Back?

Imagine this: You're enjoying your sauna session, and suddenly, you spot dark spots or smell something musty. 

Wait, is that mold in a sauna? 

But that’s not supposed to happen, right?

Well, it actually can. 

You see, even though saunas are hot and steamy, mold can still sneak in when there’s moisture trapped inside. 

The good news? 

It's not the end of the world. 

Mold in your sauna is more common than you think. Also, it is something you can easily fix and prevent with just a little know-how.

In this blog, I am going to explain exactly that. We will keep the focus on three main things: 

• Why mold grows in saunas
• How to remove mold in sauna 
• How to prevent mold from coming back

So, let’s get started.
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Key takeaways

• Mold can grow in saunas despite the high heat if moisture lingers
  
  
• Most sauna mold is surface-level and removable
  
  
• Harsh chemicals can damage sauna wood and pose health risks
  
  
• Proper drying and ventilation is more important than scrubbing
  
  
• Preventing mold is easier than removing it

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First thing first, how to tell if it is really mold in sauna?

Before you start to fret, let’s make sure what you’re seeing is actually mold. 

You see, it is easy to mistake a few dark spots for mold. But sometimes, it's just something else.

So, take a deep breath, and let’s break it down.

Sometimes, what looks like mold isn’t mold at all. Here are a few things you might spot in your sauna that aren’t actually dangerous mold:

• Heat stains: Over time, the wood absorbs the heat, and this can cause dark spots on the surface. 
• Water marks: Sweat, steam, and condensation can leave behind marks on the wood. 
• Natural wood knots: If your sauna is made of cedar (or any type of sauna wood), you might notice some natural knots or discolorations.

But here are some visible signs of mold that you should not ignore: 

• Fuzzy spots (black, green, or gray): Mold shows up as fuzzy spots on the wood. The colors can vary and they’re most commonly black, green, or gray. These fuzzy patches are a good sign you’re dealing with mold and not just a stain or mark.
• Musty or damp smell: Mold has a very distinct, musty smell. If your sauna starts to smell damp or like something’s been left wet for too long, it might be mold.
• Spots that spread over time: If the dark spots on your sauna start to grow, spread, or show up in different areas, it’s probably mold. 

It appears in specific areas: Mold often shows up in places that are harder to dry, like corners, under benches, or near the floor. ​
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In short, here are the signs that it is actually mold in sauna:

Sign	What to Look For
Fuzzy Spots (Black/Green/Gray)	Soft, fuzzy growths on the wood surface
Musty Smell	A strong, earthy, musty smell that doesn’t go away
Spreading Spots	Dark spots that grow larger or more frequent
Specific Areas	Mold often shows up in corners, under benches, or near the floor

Bonus: Here’s how to tell whether it’s mildew or mold:

It is not very difficult to tell the differences between mold and mildew. 

If the spots you’re seeing wipe away easily and don’t come back, it’s likely mildew, which is much less serious and easier to manage. 

But if the spots keep reappearing no matter how many times you clean them, you’re dealing with mold.
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But why is there mold in your sauna?

You might think mold would never show up in a sauna because it’s so hot in there. But it actually can.

Mold usually grows after your sauna session ends. And it happens because three things come together:

1. Moisture: All that sweat, steam, and condensation needs to dry out. If it doesn't, mold moves in.
2. Organic material (sauna wood): Your sauna is made of wood, which is like food for mold.
3. Time: Mold needs time to grow, and if moisture sits there long enough, it’ll start to spread.

So, if your sauna doesn’t dry properly, it’s providing all the perfect conditions for mold to grow.
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Here are some of the most common causes of mold in sauna:

• Not airing out the sauna after use: Leaving the sauna closed up with moisture inside is like inviting mold in. 
• Poor ventilation: Without good airflow, moisture has nowhere to go. This is especially common in outdoor saunas where vents might get blocked.
• Sitting sweat-soaked towels directly on benches: If you’re leaving wet towels on the benches, the wood stays damp for longer.
• Leaving the door closed after your session: After you’re done, if you leave the door closed it will trap heat and moisture inside.
• Humid climate or rainy weather: If you live in a humid area, moisture hangs around longer, making mold more likely.

Rare or inconsistent sauna use: If you don’t use your sauna regularly, moisture can stay trapped in the wood for too long.

In short, here’s why you see mold in your sauna:

Cause	Why It Happens
Not airing out the sauna after use	Traps moisture inside, encouraging mold growth
Poor ventilation	Moisture has nowhere to escape, especially in outdoor saunas
Sitting wet towels on benches	Wet towels trap moisture in the wood
Leaving the door closed after use	Moisture and heat stay trapped inside
Humid weather or rare sauna use	Moisture lingers longer, making mold more likely

How to remove mold in sauna step-by-step?

Okay, now that you know what mold looks like and what causes it, it’s time to get rid of it the right way. 

I am going to break this down into easy steps so you can clean your sauna without causing any damage to the wood or putting your health at risk. 

And this is different from my regular sauna cleaning guide, so do read it carefully. 

Ready? 

Let’s get into it.
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Step 1: Let the sauna dry completely

Before you start scrubbing away at the mold, give your sauna some time to dry out completely.

Run the sauna for about 30-45 minutes with no one inside. This will do a few important things, such as:

• The hot air will kill any mold spores that are there on the surface of the wood.
• Sometimes moisture gets trapped in places you can’t see. So, running the sauna will help dry up that hidden moisture.
• Once the wood has dried out, the mold will come off a lot easier.

After running the sauna, let it cool down for a little while before you start cleaning. This will make the process safer and easier.
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Step 2: Use a sauna-safe mold cleaner

Here’s a big one: Avoid bleach, ammonia, or any harsh disinfectants.

While they might seem like a quick fix, these chemicals can actually damage the wood over time and release harmful fumes when the sauna heats up again. 

Not to mention, you don’t want to breathe those fumes in. 

Instead, go for safer, gentler cleaners that will still do the job without causing any damage.

Here are some options that work great:

• White vinegar and water (mix them in a 1:1 ratio): It’s natural, effective, and won’t harm the wood.
• Borax and warm water: You can use borax to kill mold as it is safe for sauna wood.
• Mild sauna-approved wood cleaner: If you’ve got a cleaner that’s made specifically for saunas, this is your best bet. 

Also, when you’re applying the cleaner, always use a soft cloth or sponge and never a wire brush. 

Wire brushes might seem tough, but they can scratch the wood, which could lead to more problems down the line.
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Step 3: Gently scrub the affected area

Now, it’s time to get rid of the mold. 

Grab your cloth or sponge and start scrubbing gently. 

Always scrub with the grain of the wood, not against it. This will prevent damage and keep the wood looking nice. 

Also, focus only on the moldy spots, and don’t go overboard and scrub the entire sauna unless you really need to.

Another important rule: Don’t soak the wood with water. 

Using too much water can actually make things worse by trapping moisture in the wood. So, just keep the cloth damp, not soaking wet.
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Step 4: Wipe with clean water

After you’ve scrubbed away the mold, grab a clean, lightly damp cloth and wipe down the wood again to remove any leftover cleaner. You don’t want any cleaning solution left on the surface, so give it a good wipe down.

Once that’s done, let the sauna air dry completely. Don’t rush this step as it’s important that everything dries out fully before you move on.
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Step 5: Heat-dry again

Once the sauna is clean and dry, it’s time for one last step, running the sauna again. 

This will help make sure no moisture gets trapped in the wood, and it will also prevent mold from coming back too quickly. 

Run the heater for a little while, 15-30 minutes should be enough. This final heat-dry step ensures:

• No moisture is left behind that could invite mold back.
• Any remaining spores are killed off before they have a chance to grow.

And there you go! 

These steps will help you get rid of that mold and keep your sauna safe, clean, and healthy to use.
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In short, here are all the steps to remove mold in sauna:

Step	What to Do	Why It Works
Step 1: Let the Sauna Dry Completely	Run the sauna for 30-45 minutes with no one inside to dry out moisture.	Heat kills surface mold spores and dries trapped moisture.
Step 2: Use a Sauna-Safe Mold Cleaner	Mix white vinegar + water (1:1) or use a mild sauna cleaner. Apply with a soft cloth.	Gentle cleaners won’t damage the wood and are safe to breathe.
Step 3: Gently Scrub the Affected Area	Scrub moldy spots gently with the grain of the wood. Don’t soak the wood with water.	Prevents wood damage and removes surface mold without making it worse.
Step 4: Wipe With Clean Water	Use a lightly damp cloth to wipe off any cleaner residue.	Ensures all cleaning solutions are removed and prevents buildup.
Step 5: Heat-Dry Again	Run the sauna again for 15-30 minutes to dry everything completely.	Ensures all moisture is gone, stopping mold from coming back right away.

Bonus: Cedar saunas are not mold-proof

Cedar is a popular choice for building classic barrel-shaped outdoor saunas because it’s naturally resistant to mold. But it’s not completely mold-proof. 

Cedar wood is soft and porous, which means mold usually stays on the surface rather than soaking into the wood. That’s good news as you can remove the mold with just gentle scrubbing.
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How to prevent mold from coming back?

Now that you’ve removed the mold, you want to prevent it from coming back. 

And it is possible. 

Here’s what you need to do to keep your sauna mold-free:
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1. After every sauna session

• Leave the door open: After you’re done, don’t just close up the sauna. Leave the door open for a while to let the steam escape and the sauna air out. This helps moisture dry up faster and stops mold from growing.
• Run the heater for 15-30 minutes longer: If possible, run the sauna for about 15-30 extra minutes after you’re done. This helps dry out any remaining moisture inside.
• Hang towels outside the sauna: Wet towels left inside can trap moisture, so always hang them outside the sauna to dry.

Wipe benches if they’re heavily soaked: If the benches are really wet, wipe them down with a clean towel to remove excess moisture before it has a chance to sit.

2. Once every month

• Air out the sauna fully: Give your sauna a good airing out at least once a month. Open the door, and let it breathe for a few hours. This will help keep everything dry and fresh.
• Check corners, under benches, and floors: These areas are the most common places for mold to hide. So, make it a habit to check them regularly and wipe them down if needed.

Lightly wipe surfaces if needed: If you notice any buildup of sweat or steam, give the surfaces a quick wipe to keep them clean and dry.
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3. Fix the sauna design and setup (if needed)

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• Proper intake and exhaust vents: A good sauna ventilation is much less likely to cause mold. So, make sure the sauna has both intake and exhaust vents to help the air flow and moisture escape.
• Breathable wood (no thick sealants): Avoid using thick sealants that trap moisture in the wood. The best saunas use breathable wood that lets air flow through, which prevents mold growth.

Benches with airflow underneath: Benches that are raised slightly or have airflow underneath are perfect because they allow air to circulate and moisture to escape more easily.
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In short, here’s how you can prevent mold from coming back:

Action	Why It Helps
Leave the door open after use	Lets steam and moisture escape quickly
Run the heater 15–30 minutes longer	Helps dry out any remaining moisture
Hang towels outside	Prevents towels from trapping moisture inside
Wipe wet benches	Removes moisture so it doesn’t sit in the wood
Air out weekly or monthly	Keeps the sauna dry and fresh

Final words

By now, I am sure you know how to remove mold in sauna and prevent it from coming back. 

You see, mold in a sauna doesn’t mean your sauna is broken or unsafe. It simply means moisture isn’t leaving the enclosure fast enough.

But with the right cleaning method and a few simple habit changes, most sauna mold issues can be:

• Removed safely
• Prevented long-term
• And even avoided entirely in the future

Got more questions or want a sauna in your home?

You can get in touch with us!

At Steam and Sauna Experts, we design saunas with proper airflow, smart materials, and long-term durability in mind, helping prevent issues like mold before they ever start.

Whether you’re building new or upgrading an existing sauna, we are here to help.
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FAQs about mold in sauna

Why does mold grow more often in outdoor saunas?
Outdoor saunas face more mold risk because of factors like rain, humidity, and bigger temperature swings. 

The air outside is usually more damp, and when the sauna cools down, condensation can form inside. Plus, poor airflow under the benches can trap moisture. 


Is sauna mold dangerous?
In most cases, sauna mold is mild and manageable, but it’s important to be cautious if you have asthma, allergies, or a weakened immune system. 

If you notice the mold is spreading, has a strong smell, or keeps coming back right after cleaning, it’s time to get help from a professional. 

These signs could mean the mold is more serious and needs to be treated properly.


How can I prevent mold from coming back in my sauna?
To stop mold from coming back, always air out your sauna after each use by leaving the door open. 

Run the heater for an extra 15-30 minutes to dry out the moisture. Also, regularly check under benches and in corners. 

And don’t forget about proper ventilation as good airflow is key to keeping your sauna dry and mold-free. 

The more you keep moisture in check, the less likely mold will be a problem. 


Can I use bleach to clean mold in my sauna?
No, don’t use bleach.

Bleach might seem like a quick fix, but it can damage sauna wood and release harmful fumes when the sauna heats up again. 

Instead, try using a white vinegar and water mix or a mild sauna cleaner. These options are much safer for both the wood and your health. 

Stick to gentle cleaning methods to keep your sauna looking good without any risks.


How do I know if it’s mold or just a stain on the wood?
If you see dark spots, but they wipe away easily and don’t come back, it’s probably just a heat stain or watermark. 

Mold, on the other hand, is fuzzy (black, green, or gray) and usually spreads over time. It also comes with a musty smell. 

If the spots don’t disappear or seem to grow, it’s most likely mold, and it’s time to clean it up properly.


Can I prevent mold by sealing the wood in my sauna?
It’s actually not recommended to seal the wood completely in a sauna. Sealing traps moisture inside, which can make mold more likely to grow. 

Instead, use breathable wood that allows air to flow freely. Make sure the sauna has good ventilation, so moisture can escape. 


What should I avoid when cleaning mold in a sauna?
When cleaning mold, there are a few things you should definitely avoid, such as:

• Don’t pressure wash the wood, it can damage it.
• Don’t seal mold under oils or stains, as that locks it in.
• Don’t ignore moisture problems. 
• Don’t rely on heat alone to fix mold. It may kill spores temporarily, but it doesn’t solve the moisture issue.