sauna. stove

If you’ve ever been to a traditional sauna, chances are that you’ve seen your fair share of different sauna rocks placed on top of the heaters or stoves. Those rocks are there for a very good reason – they retain the heat from the stove and then return it into the sauna for a long period of time. Finding the right rocks for your heater might be a bit tricky, though, since there are quite a few different types and sizes out there. This is why we will go through all of those things in this sauna rocks guide and also check out some of the best deals for this year!

The Sauna Place 45lb Box of Sauna Heater Rocks

Our Rating: (4.5/5)

This box of replacement sauna heater stones is one of the best-rated on the market currently thanks to its good sizing and proper sauna rock types. They work great for both electric and gas sauna stoves and heaters and are even suitable for wood-fired ones. To fit most heaters’ standards, they are specifically sorted in terms of their sizes. They are mostly potato-sized and have a rough surface that stacks well and doesn’t slip.

The rocks themselves are Peridotite stones meaning they have quite a few unique features compared to other normal stones. They are dense, heavy, and coarse-grained igneous rocks (a type of volcanic rock). They withstand extreme heats and do not crack even after years of continuous usage. There are no cracks or pores on them, meaning they won’t hold moisture or water when you pour it on them. That is important if you want to prevent “pops” and even rock bursts. When you apply water, the heat these rocks produce is soft and continuous, allowing you to space out the waterings at more than 10-15 minutes apart.

Pros

  • 45 pounds of rocks
  • Peridotite
  • Specially selected
  • Great size for stacking
  • Very durable
  • Produce soft heat

Cons

  • Very expensive
  • Take some time to ship

Fino Sauna Stones

Our Rating: (4.5/5)

The Fino Sauna stones are another good option if you want to save a bit of money and get a specific type of rocks. These stones are Dolerite rock and are selected specifically to withstand fast heating and sudden cooldowns. Those two things are typical to electric sauna heaters and people who water their stones a lot. Watering the stones drops their temperature in an extremely fast way and some stones cannot withstand that sudden temperature fluctuation. This is why Dolerite rocks are a common choice for people with electric heaters that heat up very fast. These stones are also much better looking than the other type of volcanic rocks out there, making them a popular option.

The amount of stones you’re getting here is 42 lbs which is typically enough for heaters of up to 9kW of power. A more powerful heater will require more stones to keep the temperature of your sauna steady. If you have a larger heater, I suggest getting two boxes of these stones.

Pros

  • Look great
  • Dolerite rocks
  • Can withstand rapid heating
  • Very durable in the long run
  • Don’t require a lot of re-stacking

Cons

  • One box isn’t enough for large heaters
  • Not very cheap

Coasts Replacement Sauna Heater Stones

Our Rating: (4/5)

Last and maybe least on this list are the Coast SSBAG replacement sauna heater rocks. This is a 40 pounds package that includes vulcanic stones of various sizes and shapes. They work with all types of heaters and are very decently priced compared to other stone packages online. There are no pores or cracks on them which allows them to heat up fast and to withstand you constantly pouring water on top of them when they’re fully heated up.

The main issue with these stones is that you will have to clean them up before you start stacking them on top of your heater. They are also huge and are hardly stackable on smaller stoves and heaters. While big rocks hold onto heat well and distribute it evenly afterward, they are very hard to work with and can often tumble over if you aren’t careful. They are also much heavier and in a typical 40 lbs package, you will be getting far fewer stones.

As a whole, this package is good if you have a large wood-fired stove that requires big stones to be placed around and on top of it. If you have anything smaller than that, however, I suggest picking other packages with smaller overall sizes.

Pros

  • Suitable for large sauna heaters
  • No cracks or pores
  • Withstand fast heating up
  • Tolerate water well
  • Relatively good price-to-value ratio

Cons

  • Huge stones
  • You don’t get a lot of stones in the box
  • Difficult to stack on smaller heaters

Sauna Rocks Buyer’s Guide

If you are new to all this and want to browse a few local sauna stores before you pick the right rocks for your sauna, this section is just for you. Let’s start with the basics…

What are sauna rocks?

As I mentioned at the beginning of this guide, sauna rocks serve a major role in your sauna’s heat retention and continuity. They initially absorb the heat from the stove and then radiate it over a prolonged period of time. That is actually one of the principles behind the first saunas used by humans – a stove heats up massive rocks and then they are used to keep the sauna hot for hours. By pouring water on them, you instantly evaporate it into the air effectively creating steam and moisture. The more moist the air is around you, the hotter the room will feel. By splashing water on them, though, you also decrease their temperature, so you need to find the ultimate balance of your sauna’s temperature and humidity.

What to look for

There are a number of things that you should be considering before buying a bunch of rocks for your sauna. Some of the most important aspects would be:

  • The sauna rocks type
  • Sizing
  • number of rocks
  • Price

The sauna rocks type

The most common sauna rock type out there is the lava rock. Volcanic rocks (also called Igneous rocks) are a definite user-favorite for a few very good reasons. They can withstand very high temperatures for prolonged periods of time, they absorb the heat well, act stable and don’t “pop”, and are very durable in the long run. Granites are a form of Igneous rock that is a very common choice for sauna rocks. They are separated into two groups – porous and non-porous. Porous rocks absorb the water you might pour onto them as well as the humidity from around them which is extremely dangerous. That moisture inside them can make them burst once it gets to a boiling point and the pressure has nowhere else to go. This is why you should always select non-porous granite rocks if you’re set on this particular rock type.

sauna and spa

Another type of rock commonly used in saunas is the Peridotite rock. It is again a vulcanic rock, similar to the granite, but is a bit more coarse and dense, making it heavier. They are often imported from Finland and other Scandinavian countries.

If you’re set on finding rocks from nearby locations, lake rocks are also a good option. They are typically smaller and much easier to stack. They also tend to have no pores and are much smoother. Other rocks you can research for are Olivine, Basalt, Gabbro, or simple Vulcanite.

Sizing

The size of the rocks you choose matters for a few reasons. First, if you have a small heater, you won’t be able to fit in those giant rocks that you and your family brought along. Secondly, smaller rocks simply stack better and are much easier to arrange. I am not saying you should be going for pebble-sized rocks but look for ones that are around the size of a potato. Those allow the best mix of airflow and stackability. The only benefit of larger stones is that they tend to hold heat much better and release it over a longer period of time, ultimately keeping your sauna hotter with less energy required.

Number of rocks

If you want to buy a pack of rocks online, look for the number (or amount) of rocks that you will be getting. Most packs are measured in lbs but it is helpful to know the average dimensions of each rock and how many of them you’re getting so that you can determine whether or not that will be enough for your heater’s rock tray. Some heaters also have weight limits. For instance, most small to medium heaters have a limit of 50-60 pounds, so look for packs that are around 40 pounds, as that would be ideal.

Price

The weight of the package (40, 45, 50lbs) will also determine the shipping costs. 40-pound boxes tend to add up on your shipping fees quite a lot, especially if they are coming from a foreign country like Finland or Iceland. This is why you should always keep an eye at the total cost of the package and if it becomes too expensive for you, look for local options to find stones.

If you want to check out some of the best sauna heaters for this year, click here!

How to prepare and arrange your sauna rocks

Before you start using them, you should do a few things to your newly acquired sauna rocks (especially so if you’ve gathered them from the outdoors). Run them under clean water from your tap until the water coming down is crystal clear. Brush them off if there are some harder debris stuck to them. Once they are perfectly clean, start arranging them on your heater. Put them loosely next to each other with enough space between them to allow for air to circulate freely. The more air goes around them, the faster they will heat up, and the hotter they will keep the sauna once they are up to the right temperature. Allowing space between them also gives the heater more room to work with, as some heaters can quickly overheat if you’ve stacked the rocks too close to one another on top. That will trigger the heater to switch off due to the excessive heat. If that happens, re-order the stones and try one more time.

Once you’ve set your rocks on top of your heater, it is important to create a habit of checking the rocks from time to time. Look for newly-formed pores or cracks that can take water and burst the rock.

Learn how to clean your whole sauna by visiting my full article on the topic

Frequently Asked Questions

How much water can you splash on your sauna rocks?

As we already discussed, splashing water onto your sauna rocks increases the humidity inside but also decreases their temperature. This is why you should aim to find the perfect balance between cooling them off and your heater’s ability to bring them back up to the right temperature. As a rule of thumb, you want to add water once every 15 minutes, so for a 30-minute session that would be once in the beginning and once around the middle of it. If you plan on doing multiple 15-minute sessions, pour some water at the beginning of each time. Have in mind that the more you go in and out the more humidity you let out as well, so if you want a nice, hot, and humid sauna, you should be pouring water more often.

Should sauna rocks be replaced?

Most sauna rocks will easily outlast your heater and should, therefore, not be replaced as often. If you want to improve their performance, you can either rearrange them or even clean them with a metal brush, depending on their state. Most rocks are very thermally stable (lava rocks) and can withstand decades of continuous use.

What kind of sauna rocks should I use in my sauna?

Look for igneous rocks that have rough surfaces. Peridotites and vulcanites are an excellent choice for sauna stones

Conclusion

Finding the best sauna rocks for your heater won’t be an easy task but you still have a ton of options. You can buy a lot of different rock packs online and you can also explore certain regions and sort out the rocks that you need for free! Look for specific sizes that will stack well on top of your heater as well as the specific rock types that can withstand high heats and hold these high temperatures for longer periods.