How to Prevent Mold and Mildew in a Sauna

A good sauna is a purchase you keep for a decade or more, so it is fair to ask how to prevent mold in a sauna before you buy or right after your first few sessions. Mold and mildew need one thing to grow: trapped moisture. Saunas that dry out fully between uses almost never develop it, while a damp bench or a puddled floor left overnight is exactly the condition mold looks for. The good news is that keeping a sauna clean takes minutes, not hours, and the same moisture rules apply to a cold plunge. This guide walks through what works, what to skip, and how each sauna type compares.

The short answer

To prevent mold in a sauna, remove moisture fast and keep it low. After every session, wipe down the benches, backrests, and floor with a dry towel, then leave the door open and let the room breathe so the wood dries completely. Run a traditional or steam sauna hot with the door cracked for about 20 to 30 minutes after use to drive out humidity. Clean surfaces monthly with mild soap and warm water, never bleach or harsh sprays, which damage wood and hurt air quality. The U.S. EPA advises keeping indoor relative humidity below 60 percent, and drying any wet material within 24 to 48 hours, because that window is when mold takes hold. Cedar and other sauna woods carry natural oils that resist mold, but they still need airflow. A dry sauna is a mold-free sauna.

Why saunas get moldy (and why most do not)

Mold spores are everywhere in normal air. They only become a problem when they land on a damp organic surface and stay wet. In a sauna, that means sweat and steam soaking into bench slats, floor corners, and the gap behind a backrest, then sitting there overnight without airflow. The CDC notes that mold grows wherever moisture collects, so the fix is always the same: control the water, and you control the mold.

This is also why sauna type matters. A dry infrared sauna runs at lower temperatures and produces far less standing moisture than a steam room or a traditional Finnish sauna where water is poured on hot rocks. If low upkeep is a priority, a dry-heat cabin from our infrared saunas collection is the most forgiving choice. Outdoor cabins face the most exposure from rain, snow, and humidity swings, so if you are shopping our outdoor saunas for sale, plan for a little more routine drying and airflow.

A simple routine that keeps a sauna clean

Prevention is a habit, not a project. Three layers cover almost every situation.

After each session

Wipe the benches, backrests, and floor with a clean dry towel to lift the sweat and condensation. Prop the door open so warm, damp air escapes and fresh air moves through. For a traditional or steam sauna, leave the heater on for another 20 to 30 minutes with the door cracked so the wood bakes dry. Pull any removable floor mats out to air.

Weekly

Give high-contact spots a closer look. Vacuum or sweep the floor, check corners and the underside of benches where moisture hides, and confirm the ventilation gaps are clear. If your space runs humid, a small hygrometer lets you keep the room in the 30 to 50 percent range the EPA recommends.

Monthly

Do a deeper clean with a rag, warm water, and a mild, unscented soap. Scrub the benches and floor lightly with the grain, then dry everything and let the room ventilate. Every 3 to 6 months, many owners treat cedar benches with a food-safe paraffin sauna oil, which helps the wood shed sweat instead of soaking it in. Our broader sauna maintenance and care guide covers heater, stone, and seasonal upkeep in more detail, and the step-by-step in how to clean an infrared sauna is a handy companion.

What to avoid

A few common instincts backfire. Do not use bleach, ammonia, or scented all-purpose sprays inside a sauna. The heat drives those chemicals into the air you breathe, and they can bleach or dry out the wood. Do not seal or varnish interior sauna wood the way you would outdoor decking, because a film finish traps moisture and gets sticky at high heat. And do not leave wet towels, swimsuits, or bath mats sitting in the cabin between sessions, since they hold the exact dampness mold needs.

How sauna types compare for mold risk

All saunas stay clean with the same basic care, but some demand less of it. Here is a quick comparison to set expectations.

Type	Moisture level	Relative mold risk	Key habit
Infrared (dry heat)	Low	Lowest	Wipe sweat, air out
Traditional Finnish	Medium to high	Moderate	Bake dry after use
Steam sauna	High	Higher	Ventilate, dry fully
Outdoor cabin	Weather-driven	Moderate	Check airflow, seasonal care

Do not forget the cold plunge

Standing water makes a cold plunge the higher-risk half of a recovery setup. Mold and biofilm form when water sits untreated, so keep sanitation running with a filter plus ozone, UV, or a low dose of chlorine or hydrogen peroxide, and keep the tub covered when it is idle. Drain and refresh the water on the schedule your model recommends, and wipe the waterline and lid seals where residue builds. If you are comparing our cold plunge tubs for sale, models with built-in filtration and ozone make clean water far easier to maintain. The full routine lives in how to keep cold plunge water clean.

If you already see mold

Small surface spots on sauna wood can usually be handled at home. Ventilate the room, put on gloves, and scrub the area with warm water and a little mild soap or a diluted white vinegar solution, then dry it thoroughly and run the sauna warm to finish drying. Lightly sanding a stubborn spot on bare wood often removes the last of it. If mold covers a large area, keeps returning, or has soaked deep into the wood, replace the affected boards and find the moisture source. The CDC advises that no matter the type of mold, the goal is simply to remove it and stop the moisture that fed it. Anyone with asthma, allergies, or a weakened immune system should let someone else handle the cleanup, and see a clinician if symptoms appear. This guide is educational and is not medical advice.

Frequently asked questions

Do infrared saunas get moldy?

Rarely. Infrared saunas use dry heat and produce little standing moisture, so mold is uncommon as long as you wipe away sweat and let the cabin air out after each use. They are the lowest-maintenance option for anyone worried about upkeep.

Can I use bleach to clean a moldy sauna?

No. Bleach and other harsh chemicals damage sauna wood and release fumes when the room heats up. Use warm water with a mild soap, or a diluted white vinegar solution for spot cleaning, then dry the surface completely.

What humidity keeps a sauna mold-free?

Between sessions, aim to keep the surrounding space below 60 percent relative humidity, and ideally in the 30 to 50 percent range that the EPA recommends for mold prevention. Good ventilation and full drying after each use do most of the work.

Keeping a sauna clean comes down to airflow and dry wood, and it takes only a few minutes per session. When you are ready to choose a unit built to last, our team can help you weigh dry infrared, traditional, and outdoor options. Restore Suite is an authorized retailer with free U.S. shipping, HSA and FSA eligibility, and real human support, so you can buy from a vetted sauna retailer with confidence.