Sauna Rocks: What They Do, Which to Choose, and How to Use Them
Sauna rocks are more than decoration—they’re the thermal engine that delivers that dry, penetrating heat sauna users love. But not all sauna stones are created equal. In this guide, we’ll break down the best rocks for your sauna heater, how they affect heat quality, and the right way to use water with them for steam.
What Do Sauna Rocks Actually Do?
Placed directly on top of a sauna heater, these rocks absorb and radiate heat evenly throughout the space. When you pour water on them, they create löyly—the burst of steam that intensifies the heat and humidity. The quality and type of rock determine how much heat is retained, how evenly it disperses, and how long it lasts between heat cycles.
Best Types of Sauna Rocks
Look for igneous, high-density stones that can withstand repeated high-heat exposure without cracking or fragmenting.
- ✔ Peridotite: Dark gray or green volcanic rock, holds heat well, long-lasting
- ✔ Olivine Diabase: Found in many commercial saunas; resists breaking, great for steam
- ✔ Vulcanite: Natural basalt, good for consistent radiant heat
- ✔ Gabbro: Durable and dense, less common but great heat retention
- ❌ Avoid: River rocks, granite, or any stone with cracks or shine—they can explode when heated
How Many Sauna Rocks Do You Need?
The amount of sauna rock needed depends primarily on your heater’s design and manufacturer specifications, not just the size of your sauna. Here's a general idea:
- ⚡ Wall-mounted electric heaters: typically 40–100 lbs
- 🔥 Large floor-standing or wood-burning stoves: 150–300+ lbs
- 📦 Always refer to your sauna heater's manual for rock capacity
Overloading or underloading the rock tray can affect heat-up time, energy efficiency, and steam quality—so follow the specs closely.
Should You Add Water to Sauna Rocks?
Yes—but only with dry sauna heaters specifically designed for it. Pouring a ladle of water over hot sauna rocks temporarily raises humidity, intensifying the sensation of heat and sweat. Don’t overdo it—1 ladle every 5–10 minutes is usually ideal.
⚠️ Never pour water on infrared heaters or electric models not rated for steam—it can damage the unit or be dangerous.
How Often Should You Replace Sauna Rocks?
- 📆 Replace every 1–2 years for residential use
- 🔄 Commercial saunas may need to rotate or replace rocks every 6–12 months
- 🔍 Check regularly for cracking, dust buildup, or uneven heating
Cleaning Tip
While sauna rocks don’t need direct scrubbing, debris from sweat, minerals, and ash can accumulate. If you use water regularly, clean your heater, floor, and benches weekly with a plant-based sauna-safe spray to prevent mold and extend heater life.
Final Thoughts: Choosing the Best Sauna Stones
High-quality sauna rocks are essential for traditional dry saunas. Choose dense, heat-tolerant stones like peridotite or olivine diabase, and avoid decorative or cracked rocks. Used properly, these stones create the perfect balance of dry heat and steam—and make every session more satisfying.