The default sauna wall. For good reason.
The PROSAUNAS Thermo-Aspen 1×4 T&G STS4 Wall Cladding is 0.59″ thick and 3.54″ wide, with 3.1″ of coverage once the tongue seats into the groove. Available in 6, 7, 8, and 10-foot lengths. This is the width most people picture when they picture a sauna: even, calm, and simple to run top to bottom without the wall getting busy.
Why Thermo-Aspen
Cladding is where thermal modification earns its keep. An untreated board in a hot, humid sauna will pull in moisture, swell against its neighbor, and over a few seasons the seams start to move. Thermo-aspen has already been through extreme heat and steam, no chemicals ever, which changes the wood at a cellular level so it can’t hold moisture and won’t expand and contract. The warm golden-brown color runs all the way through the board, so a cut end at the ceiling line matches the face and the room reads as one piece.
One honest note: every sauna wood is soft and will scratch, and thermal modification doesn’t change that. The upside is you can sand it back and refinish it years from now without hurting a thing.
Specifications
- SKU: PS-THERMO-ASPEN-1X4-TG-STS4
- Species: Thermo-Aspen (thermally modified)
- Profile: 1×4 STS4 tongue-and-groove wall cladding
- Actual width: 3.54" (3.1" coverage per row)
- Actual thickness: 0.59"
- Process: heat and steam only, no chemicals
- Made in: Estonia
- Sold by: the linear foot
Where it goes
Walls and ceilings. Pair it with our Thermo-Aspen or Thermo-Spruce bench wood for a matched interior, or run a wider profile as a contrast band. Narrower coverage means you use a few more linear feet per wall than a wide board, so do the math before you order and reach out if you want us to check it.
Shipping and samples
Sold by the linear foot. Shipping is a flat $795 in the continental US, or free with a heater order. Not sure on the board count? Text your name and address to (844) 565-1113 for free samples.
Call Ben² at (844) 565-1113 if you’d like to walk through the board count before you order.

Prebuilt
Sauna Brushes
Vents