Why Are There Rocks in a Sauna? (And What Kind)

I’m sure there have been times when you were relaxing in your sauna, wondering why the rocks were even there. Believe it or not, this is a question many people ask themselves. So why are there rocks in a sauna? 

The rocks inside of the sauna are used to regulate the temperature and produce steam. Before going into the sauna, you will use the thermostat to select the temperature you want. Once the temperature has been reached, the heat shuts off, and the rocks take over. The stones then absorb the heat and regulate the temperature inside the sauna.

Continue reading If you’re still curious about why rocks are used in saunas and what kinds of rocks are used.

Why do saunas have rocks in them?

People love saunas because of their therapeutic and relaxing properties. Without the stones and the steam they create, it would be like standing outside on a sunny day.

Saunas work by heating the rocks with either wood or an electric heater. Once the desired temperature is reached, the rocks absorb the heat and produce steam when water is drizzled on them. These rocks can keep the sauna warm for 1-3 hours.

Saunas have a fascinating history. From the time saunas were created back in 2,000 BC, they have used rock and fire to produce heat. Some people believe that the first type of sauna was built in a cave with animal hides to cover the entrance to hold in the heat. Saunas were first used to cook, stay warm, and sterilize the house.  

Although people don’t use them to survive in today’s society, they still work in basically the same way. The stones help the sauna maintain the temperature, so it stays warmer for longer periods. When people pour water over the hot rocks, it creates steam which in turn increases the humidity.  

Which saunas use rocks?

There are six main styles of saunas with a few extras thrown in. While the majority of them require sauna heater rocks, there are a few types that don’t. 

Saunas that use rocks:

  • Traditional Finnish sauna
  • Dry sauna
  • Wet sauna
  • Electric sauna

Do infrared saunas have rocks?

Infrared saunas are designed to mimic the heat of the sun. Think about those cold mornings when you get in your car and turn on the heat. If it’s a bright sunny day, you’ll be turning off the heat before too long because the sun has warmed you.

Infrared saunas work in the same way: the light warms you up without making the air hot. 

Many people wonder if infrared saunas are safe. They are safe because, unlike UV rays that heat the air, infrared saunas heat your body instead. These saunas are also believed to warm your body more quickly, so it doesn’t take as long to start seeing the benefits.

How do sauna rocks work?

Saunas work by heating the rocks by using wood, fire, or an electric heater. As the temperature of the sauna increases, the stones absorb the heat. Once the desired temperature is reached, the heat source will turn off. 

Stones naturally absorb heat, making them perfect for keeping the sauna warm for long periods of time without having to worry about smoke getting inside. When the water is poured over the rocks, the sudden change in temperature causes steam.

The water will cause the stones to cool down very little, but they should hold enough heat to keep the sauna going for 1-3 hours.

Is it okay to pour water on sauna rocks?

When you first get into the sauna, you may be tempted to throw too much water on the rocks, thinking it will increase the heat. Instead, you are causing the rocks to cool off quicker than they usually would.

When first entering the sauna, take a less is more approach. Most of the time, you’ll notice a ladle by the water. You can fill it halfway at first.

Sprinkle that on the rocks, and then in about 5 minutes, if you think you need more, you can do a little more. 

What kind of rocks do you use in a sauna?

Many people don’t realize how important it is to choose suitable rocks for their sauna. The type of rocks you choose impacts if your sauna stays warm once the heat turns off. If you don’t use the correct stones, you will also notice that the steam isn’t as comfortable or as effective. 

The rocks used in saunas get up to 932°-1,472°F. While you don’t need to measure the rock’s temperature before use, it is good to keep in mind that if the rocks are too cool, the water will steam up and bubble on top of the rock. The best way to find out if they are hot enough is to put water on them. If they sizzle when you throw water on them and create instant heat they are at the right temperature.

When choosing stones for your sauna, you have to pay attention to the ones you choose. While there are many good choices, there are also bad choices. You don’t want a stone that will not steam well or crack under too much heat. The best types of sauna stones are granite, grabo, basalt (all igneous rocks), jade, and soapstone.

If you want to save money, you can collect your rocks. This takes more time than purchasing them from a store and a whole lot more effort. Another thing to point out about going this route is that you can grab the wrong type unless you know your rocks. If you have ever carried rocks, you know how dirty you can get and how heavy the stones are. I would always choose to purchase them rather than try to find acceptable stones in the wild.

The right stones matter. The size of the stone, density, porosity, and surface all matter in how well they heat the sauna and put off steam. Small stones won’t hold heat long, and if they are too large, they take longer to absorb heat. When they have a rough texture, they will hold the water longer than those that are smooth.

Dark rocks absorb heat better than those that are lighter in color. Think about wearing black clothes in the sun and how different it feels if you’re wearing light-colored ones. The same principle applies to rocks. 

Another rule of thumb is if you can scratch the rock’s surface, it’s not a good choice. This is because they are soft and will make popping noises when you drizzle water on them.

Igneous rocks

Overall, igneous rocks are the best choice for use in a sauna.

Igneous rocks are formed when lava is released from a volcano and then cools down to form magma. There are many different types of rocks in the igneous family, but they are all excellent at absorbing and storing heat.

The most popular igneous stones for saunas are:

  • Granite
  • Grabo
  • Basalt

Each of these is heavy and has a rough surface making them the perfect ones to hold heat. They tend to stay hot an hour longer than many other types of stones.

The potential downsides of these types of stones are that they can take a long time to heat up because they are so dense, and they’re generally gray and a bit dull. A lot of people like sauna stones that have color because they believe it’s more calming. 


Jade forms when earthquakes make cracks in the earth or along fault lines. Because of the high pressure in the rocks pressing together starts to form jade as a protective barrier. 

Not only is jade heat resistant and very strong, but it’s also one of the most beautiful sauna stones available. The strength of stones determines their thermal stability and if they are heat resistant. Jade is ideal because it heats up quickly and cools down slowly, meaning you don’t need as much water.

The downside of jade is that they need to be replaced frequently, and they’re quite expensive.


Like the other types of sauna stones, soapstone is formed when pressure builds up within the earth’s surface.

It is resistant to high temperatures up to 2,912°F and has good thermal conductivity. Like jade, soapstone does not require much water for steam. 

Similar to igneous rocks, soapstone is fairly dull to look at, although it’s an ideal sauna rock otherwise.