Home › Guides › Sauna Stones: Which Rocks, How Many, How to Stack
Sauna Stones: Which Rocks, How Many, How to Stack
Stones are the heart of the steam. The wrong rock cracks or explodes; the right one gives soft, lasting löyly.
Sauna stones store the heater’s heat and flash water into steam. They take brutal thermal cycling, so the rock matters.
Which stones
Use dense, non-porous igneous stone sold as sauna stones, peridotite, olivine diabase and vulcanite are the common ones. They tolerate repeated heating and quenching without shattering. Never use river rocks or random landscape stone: trapped moisture inside a porous stone turns to steam and can crack or burst it.
How many
Fill the heater’s basket to its rated capacity, the spec is on every model in our database, usually given in pounds. A tower heater like a Harvia Cilindro holds far more stone (and gives softer, longer heat) than a compact wall heater; that stone mass is part of what you are choosing between when you compare heaters.
How to stack
- Rinse off dust first, then stack loosely. Air needs to move up through the pile.
- Bigger stones at the bottom, smaller toward the top. Do not wedge them tight, packing kills airflow and overheats the elements.
- Let the stones, not the elements, be what the water hits.
Upkeep
Stones crumble over time from the thermal shock. Restack once a year, discard any that are cracked or flaking, and top up. Budget for a full replacement every couple of years of regular use.
FAQ
What kind of stones go in a sauna heater?
Dense igneous sauna stones, peridotite, olivine diabase or vulcanite. They survive repeated heating and quenching. Never use porous river or landscape rock, which can crack or explode.
How often do sauna stones need replacing?
Restack and inspect yearly, discarding cracked or flaking stones. With regular use, plan on a full replacement every couple of years.