How Long do Sauna Stones Last?
How long sauna stones will last is not an exact science. General guidelines are 1-2 years for high use residential saunas, while commercial sauna stones may wear out as quickly as 6 months.
However, sauna stones that are used less frequently can last much longer. For example, saunas at remote/vacation properties that aren't used as often can last several years without any issue.
Sauna stones only need to be replaced when the stones are showing signs of damage though. As long as they aren't breaking down, they can continue to be used.
Why Good Sauna Stones Matter
Old sauna stones that have begun deteriorating can reduce performance by blocking the airflow in the heater. As they break down they can close the gaps that the air needs to flow through.
This not only impacts the ability for the stones to heat up properly, but it can also damage heaters or cause them to function improperly. Electric sauna heaters have heat safety limits that will shut the stove off when triggered. Poor airflow can allow the heat to build up and trigger these safeties. Having this repeatedly happen can cause damage to the stove as it repeatedly turns on and shuts off.
Even in cases where the stove still functions properly with limited airflow, it can hurt the performance of the stove. For electric stoves this means a higher energy bill and more wear on the heating element, and with wood stoves it means more firings before the sauna gets up to temperature.
How Often to Check Stones
The general recommendation is to check the stones once a year to see if they are degrading. However, sauna stones are resilient and can last several years without needing to be replaced.
Frequency of use, how hard your water is, and your heater type can affect how often you need to replace the stones though. Using the sauna daily with hard water will of course increase how much wear is on the stones.
Electric heaters also tend to wear the stones a little more than wood fired stoves because of the heating time. Electric heaters warm faster than wood stoves. This rapid heating cycle is harder on the stones than the more gradual heating cycle of a wood stove. That said, this typically has a minimal impact on the stones lifespan and isn't something to get too focused on if you're split between choosing between an electric or wood fired heater.
How to Stack Sauna Stones
A good practice for any sauna owner is to take the stones out of the stove once a year and restack them. Stones should be placed as if they were tossed them on top of the stove (don't actually toss them into the stove though). Stones shouldn't be packed tightly together. Air needs to flow between them properly and each sauna heater/stove will have capacity ratings for how many stones are intended to fit.
For wood stoves, this capacity rating is typically for stoves with the chimney installed in the rear of the stove. When the chimney is installed in the top of the stove, the space it takes up will somewhat limit how many stones fit into the stove.
This is a great opportunity to look over the stones for discoloration and damage. Any stones that are starting to crumble or become discolored should be replaced. But as stated earlier, if there are no signs of damage, continue using them without concern.