Most sauna wood decisions come down to one question: how light do you want the room? If the answer is “as light as possible,” this is the board.
This is the ProSaunas Aspen 1×4 STS4 tongue-and-groove wall cladding, the smooth-four-sides profile that’s been the workhorse of Nordic interior sauna walls for generations. Each board is 15mm thick (about 0.59″) and 90mm wide, with 80mm of net coverage. The STS4 groove is narrow and angular, so the shadow line is crisp and tight. Installation is standard horizontal or vertical T&G: fit the tongue, face-nail or clip, move on. Boards come in lengths from 1 ft to 10 ft, sold by the linear foot, so you can mix lengths and minimize waste. Milled in Estonia from straight-grained aspen selected for uniform texture and a pale creamy tone.
Why Aspen
Aspen is the Scandinavian default for a reason. It stays cool to the touch even at full heat, has zero resin bleed, and won’t splinter under bare skin. The color is the lightest we carry in any non-modified wood: a near-white cream that keeps a small room from feeling heavy. We haven’t heard of anyone having an allergic reaction to aspen, which is not something we can say about cedar. One honest thing to know: this is natural (not thermally modified) aspen, so it moves a bit more than thermo-aspen through the repeated heat-and-cool cycle. Over time that can mean slightly wider gaps at the groove joints. If dimensional stability is your top concern, our thermo-aspen cladding is the step-up at a comparable price. If you want the palest possible tone and a true Nordic feel, this is it.
Specifications
- SKU: PS-ASPEN-1X4-TG-STS4
- Species: Natural Aspen
- Profile: STS4 smooth-four-sides tongue-and-groove
- Thickness: 0.59″ (15mm)
- Width: 3.54″ (90mm)
- Coverage: 3.1″ (80mm) per board
- Available lengths: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ft
- MAP: $4.41 per linear foot
- Milled in Estonia
Where it goes
Walls and ceilings, horizontal or vertical, in any sauna style. Works especially well in contemporary Nordic rooms, compact barrel saunas, and any build where you want maximum brightness. Pair with our aspen 2×3 or 2×6 bench boards for a fully matched room, or mix with thermo-aspen bench material if you want a warm-toned contrast at seat level. The SI inside corner trim and VA outside corner trim in matching aspen finish the room cleanly.
Shipping and samples
Sold by the linear foot. Shipping is a flat $795 to the continental US, or free when ordered alongside a heater. We offer free samples: text your name and address to (844) 565-1113 and we’ll drop one in the mail.
Call Ben² at (844) 565-1113 if you’d like to talk through the board count before you order.

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