The Harvia M3 SL is a through-the-wall wood burning sauna stove that lets you feed the fire from an adjacent room or outdoors — keeping the sauna space clean, undisturbed, and consistently warm. Designed for sauna rooms between 159 and 459 cubic feet, it combines practical installation flexibility with a cast-iron-framed glass door that frames the fire for a classic, relaxed sauna atmosphere.
Why Customers Choose the Harvia M3 SL
- Through-the-wall fire chamber keeps the sauna interior clean and uninterrupted during heating
- Cast-iron-framed glass door provides a view of the fire for a traditional sauna ambiance
- Adjustable legs allow secure installation on uneven floors
- Reversible door hinge accommodates left- or right-hand installation
- Compact footprint fits cabin, outdoor, and residential sauna builds
- Backed by Harvia, a globally recognized sauna equipment manufacturer
Product Highlights
Through-the-Wall Fire Chamber
The firebox extends through the sauna wall so firewood can be loaded from an adjacent room or outdoors, eliminating the need to open the sauna door during a session.
Cast-Iron-Framed Glass Door
A heat-resistant glass panel set in a cast-iron frame lets you observe the fire, adding warmth and character to the sauna environment.
Adjustable Legs
The stove's legs can be adjusted to compensate for uneven flooring, making installation more straightforward in a variety of sauna structures.
Reversible Door Hinge
The door can be configured to open from either side, giving installers flexibility to work with different room layouts and wall placements.
Galvanized Steel Construction
Built from galvanized metal with a black finish, the M3 SL is designed to withstand the sustained high-heat environment of regular sauna use.
Specifications
| Model | Harvia M3 SL (WKM3SL) |
| Room Capacity | 159 – 459 cubic feet |
| Dimensions | 15 3/8" W × 17" D + 8 5/8" D collar × 28" H |
| Weight | 110 lbs |
| Fuel Type | Wood |
| Max Firewood Size | 6" diameter × 13 3/4" long |
| Stone Capacity | 90 lbs (3 boxes required, sold separately) |
| Smoke Outlet | Top |
| Finish | Galvanized metal – black |
| Installation Type | Through-the-wall, floor standing |
| SKU | 120-WKM3SL |
Ideal For
- Cabin and outdoor sauna installations
- Residential saunas in the 159–459 cubic foot range
- Builders and homeowners who want external firewood access
- Sauna enthusiasts seeking a traditional wood burning experience
- Installations where keeping the sauna interior clean during heating is a priority
Important Information
- Professional installation by a licensed contractor is strongly recommended. Consult local building and fire codes before installation.
- A proper chimney system is required. Review the chimney installation documentation provided by the manufacturer before purchasing.
- The through-the-wall installation requires a correctly sized and fire-rated wall penetration. Follow all clearance requirements specified in the installation manual.
- Sauna stones (3 boxes, 90 lbs total) are not included and must be purchased separately. Use only stones rated for sauna use.
- Maximum firewood size is 6" diameter × 13 3/4" long. Do not exceed this size.
- Keep children and pets away from the stove during and after operation until fully cooled.
- This stove is designed for sauna use only. Do not use for space heating or cooking.
Frequently Asked Questions
What size sauna room is the Harvia M3 SL designed for?
The Harvia M3 SL is rated for sauna rooms between 159 and 459 cubic feet. For best results, match the stove to your room's actual cubic footage using a sauna heater sizing guide.
How does the through-the-wall design work?
The firebox collar extends through a wall opening so the fire can be loaded from an adjacent room or from outside. This keeps the sauna interior clean and allows you to add wood without opening the sauna door or interrupting the session.
Does the Harvia M3 SL come with sauna stones?
No. The stove requires approximately 90 lbs of sauna stones (3 boxes), which must be purchased separately. Use only stones specifically rated for sauna use.
Does this stove require a chimney?
Yes. The Harvia M3 SL is a wood burning stove and requires a properly installed chimney system. Consult the manufacturer's chimney installation documentation and a licensed installer before purchasing.
Can the door be installed on either side?
Yes. The door hinge is reversible, so it can be configured to open from the left or right to suit your installation layout.
What is the maximum firewood size for the M3 SL?
The maximum firewood size is 6" in diameter and 13 3/4" in length. Do not use firewood that exceeds these dimensions.
The Harvia M3 SL is a practical, well-built through-the-wall wood burning sauna stove suited to cabin, outdoor, and residential sauna installations. If you're looking for a stove that keeps your sauna clean and your sessions uninterrupted, it's a strong option at this price point. Order today or reach out with any questions — we're happy to help you find the right fit.
This product is intended for sauna use only. It is not a medical device and is not intended to diagnose, treat, cure, or prevent any condition or disease. Consult a qualified healthcare provider before use if you have any health concerns. Always follow the manufacturer's installation and safety guidelines.