Here is how you stack rocks in your sauna heater (rock tower style or wall-mounted). The easy expert way.
Table of Contents:
- Why rock placement is important
- General rock stacking tips
- Maintenance tip
- Stack rocks in rock tower style sauna heater
- Stack rocks in wall-mounted style sauna heater
Why Rock Placement is Important
Properly stacked sauna rocks are essential for:
- Safe operation
- Faster warm-up times
- Even heat distribution in the sauna
- Reliable steam (löyly) production
- Preventing the high-limit switch from tripping
In short, stacking your rocks doesn’t mean just throwing your rocks in the heater. Take your time, do it once, and do it right. You’ll save more time in the long run.
Rock Stacking Basics
Before you begin stacking, follow these essential tips to ensure your sauna heater performs safely and efficiently:
- Ideally rinse the rocks before placing them—this removes dust that can burn off and create odors.
- Stack loosely, not tightly—you want plenty of airflow between the rocks to prevent overheating and promote even heat distribution.
- Fully cover the tips of the heating elements—this protects the heater and ensures consistent performance.
- Do not overfill the heater—follow manufacturer guidelines and avoid stacking rocks above the designated area.
- Avoid jamming rocks in place—tight stacking can block airflow and trip the high-limit safety switch.
Keeping these fundamentals in mind will help your heater last longer and create the best possible löyly (steam).
Sauna Heater Maintenance Tip
Once a year:
- Remove all rocks
- Check for cracked or crumbled stones—replace as needed
- Wipe down the heater with a damp cloth to remove lint and dust
How to Stack Rocks in Your Finnleo Himalaya Rock Tower Sauna Heater
You’ve just invested in a premium sauna experience with the Finnleo Himalaya Rock Tower heater (or another heater such as the Iki Pillar, Iki Wall, or Iki Corner) —great choice! This guide largely applies to all styles of rock tower sauna heater (with a few minor differences like the Biowater Tank). Now comes a surprisingly critical step: stacking the rocks. It might seem simple, but how you pack those stones affects heat, steam, and the life of your heater.
Done right, you’ll get consistent heat, efficient airflow, and rich löyly (steam). Done wrong? You risk poor performance or even damage to the unit.
Let’s break it down into expert-backed, easy-to-follow steps.
Step 1: Prep Your Heater and Rocks
Before placing a single rock, take the heater out of the box and check all the components.
- Don’t install the Biow Water Technique Tank yet! This goes in at about the halfway-three/ quarter point.
- Your heater should come with three boxes of stones (about 70 lbs each). These vary in size. This is important to note, the amount of rocks your sauna heater came with is the amount that is needed for your heater. You don’t want to over pack rocks in your heater as it will hurt the performance of the stove.
Step 2: Master the “Tabletop Method”
This is our go-to rock stacking strategy to maintain good airflow and ensure optimal performance of the sauna heater.
Here’s how it works:
1. Big rocks first – Start at the bottom with large, upright rocks to build height.
2. Flat rocks next – Lay flatter stones across the top of those, like a table.
3. Repeat – Keep alternating rows up the heater.
This method allows air to circulate while giving structure to the rock pile.
Step 3: Protect the Heating Elements
The heater’s elements can collapse inward if rocks aren’t placed thoughtfully. Here’s how to prevent that:
- Spacer rocks – Gently insert stones between the elements to hold their shape.
- Be careful – Don’t press rocks directly against the elements. It reduces heat transfer and can overwork the heater.
Step 4: Create the “Chimney Effect”
To maximize airflow:
- Stack rocks along the outer edge, not just the middle
- Leave space in the center so heat can rise, circulate, and fill the room quickly
- When you pour water on the rocks, this airflow keeps the heat intense and steady.
Step 5: Add the Biowater Technique Tank (at the Right Time)
After you’ve stacked most of the rocks, it’s time to add the Biow Water Technique Tank.
- Where it sits – It rests between two heating elements.
- Indoor sauna? Place it anywhere—it doesn’t make a big difference.
- Outdoor sauna? Put it in front. It’ll direct hot air toward the sensor to keep your heater cycle running smoothly.
Make sure it’s balanced and adjust the surrounding rocks if needed.
Step 6: Guard the High Limit Sensor
The sensor is on the upper back of the heater. If it overheats, your heater might shut off.
- Use your biggest rocks to create a wall behind it.
- This buffers the heat and helps the sensor stay at a stable temperature.
Step 7: Finish Strong
Near the top:
- Use smaller rocks to fill in, but don’t pack tightly.
- Air gaps are crucial – You should be able to poke your fingers in and see through some parts.
Overpacking = Bad airflow = Poor performance.
Over time, rocks will settle from heat and water. Keep your extra stones handy for future refills.
Simple Way to Visualize It
Think of stacking rocks like building a campfire:
- Big logs (rocks) on the bottom for a sturdy base.
- Spaces between for airflow.
- Layer it with intention—not just dumping them in.
Quick Tips to Remember
✅ Big rocks on the bottom, flatter ones on top
✅ Keep space between heating elements
✅ Focus on airflow, not just filling space
✅ Leave gaps—you’ll need them
✅ Repack occasionally as rocks settle
How to Stack Rocks in Your Wall-Mounted Sauna Heater
Here’s how to stack rocks in your Finnleo Designer Sauna Heater or other wall-mounted electric heater.
Sort by Size
- Separate the rocks into smaller and larger pieces
- You’ll use the smaller ones around the edges and the larger ones in the middle
Start with the Outer Sections
- Place smaller rocks tightly around the outer edges of the rock compartment
- This helps hold everything in place and creates good thermal mass
Fill the Center Section Loosely
- Place larger rocks loosely in the center of the heater
- Make sure air can easily circulate between them for proper airflow
Ensure Rocks Cover the Elements
- All heating elements must be fully covered
- This protects the elements and ensures even heat
Top It Off (But Don’t Overpack)
- Loosely cover the tops of the heating elements with a 2–3 inch layer of rocks
- Do not jam rocks in tightly—tight stacking reduces airflow and may trip the safety shutoff
Common Mistakes to Avoid
❌ Don’t pack the rocks too tightly (restricts airflow, can trip the high-limit switch)
❌ Don’t leave any heating elements exposed
❌ Don’t use other types of stones—only use the rocks supplied with your heater
❌ Don’t pour chlorinated water or pool water on the rocks
Ask The Sauna Experts For Help
If you need anything else during your journey of stacking rocks in your sauna heater, give us a call at 612.505.9700 or contact us through our website. Nearly every member of our team grew up with a sauna in the home (most of us are Finnish) and we’ve built hundreds of saunas to this point. If we don’t have the answer for you (we’re confident we will), we’ll find the answer for you.
