How to Choose Sauna Rocks

You can’t have a good sauna experience without the right sauna rocks. In this article, we’ll help you choose the perfect rocks for your sauna.

Table of Contents

Choosing the Sauna Rocks

To choose the best rocks for your sauna, you need to consider:

  • The type of rocks
  • The size of the rocks
  • How safe they are to use

Let’s take a deep dive into each option.

1. Type of Rock

Rock researchers group rocks into 3 types – igneous, sedimentary, and metamorphic. Igneous is most suitable for a sauna. It is made from cooled magma and lava. And it’s the oldest rock on Earth. 

Examples of igneous rocks are Basalt, Granite, Gabro, Peridotite, Olivine, Vulcanite, etc. 

different types of igneous rocks
Different types of igneous rocks
(Image source:

That said, not all igneous rocks are suitable for the sauna. For instance, Pumice and Obsidian are not dense enough to hold heat. So make sure you pick the non-porous, dense ones. 

You can carry out a small experiment to determine if a rock is dense enough. Use a hammer or drop the rock on a hard floor. If it breaks or chips away then the rock isn’t dense enough. It could explode when you start heating it (more on this later).

2. Size of Rock

It’s a good idea to get a variety of sizes – small, medium and large. You can place the large ones at the bottom and the medium ones at the top. Small rocks can be used to fill in gaps. But if finding a variety of rocks is difficult, then just get medium-sized rocks. 

Make sure you don’t spread the rocks too sparsely. The water will run down without soaking the rocks. But also don’t arrange them too tightly. You would still have a hard time soaking the rocks. 

3. Safety Issues

Not all rocks are suitable for a sauna. Using the wrong type of rock can lead to an explosion. So while you can collect sauna rocks from your garden and public parks, be very careful. To make sure that the rocks can withstand heat, here are a few tests you can perform:

  • Scratch it with your nails. A good rock will not chip away. 
  • Drop it on a hard floor. A good rock will not break. 
  • Throw it into the fire, heat it thoroughly and then plunge it into cold water. A good rock will not crack.

How to Prepare Sauna Rocks for First-Time Use

To prepare sauna rocks for first-time use, follow the steps below: 

Step 1: Buy or gather rocks from your garden or city park (with permission). The rocks you bought can be placed straight into the heater unless instructed otherwise. But the rocks you gathered have to be cleaned first.

Step 2: Place the rocks in the heater. If you arrange it too tightly, you risk overheating the heater. But if you arrange it too loosely, water will pass through quickly and you would have a hard time soaking the rocks.

How Often Do Sauna Rocks Need to be Replaced?

Depending on how often you use the rocks, you may need to replace the rocks every few months or once a year. If you are a regular user (3-4 times a week), consider replacing the rocks every 4 months. But if you use the rocks once a week, replacing them once a year should be enough.

How Much Water Should You Splash on Sauna Heater Rocks?

You can splash a cup of water on the sauna rocks every few minutes, instead of dumping a jug of water at one go. This will prevent flooding the heater and the rocks will last longer. Sauna rocks are sensitive to the heat and cold cycle. Bringing the temperature all the way down with a big jug of water will cause the rocks to crack. Hence, dump a small amount of water every few minutes.


That’s it, folks. We hope you enjoy your new sauna rocks and have a great sauna session. If you have any questions, leave a comment below.

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