Two-and-a-half inches square. Hot room. Years of wet towels and full adults. That’s the test. This board passes it.
The PROSAUNAS Thermo-Aspen 3×3 S4SEE SHP is a glulam engineered bench support, 2.68″ x 2.68″, built for bench legs, structural cross-supports, and any framing that needs to stay put in a high-humidity environment. Available in lengths up to 8 feet. Rounded eased edges on the S4SEE profile so it’s comfortable where bare legs might brush it.
Why Thermo-Aspen
A lot of builders frame bench legs in construction lumber and finish the seat surface in a sauna-grade wood. That works, but there’s a reason the Scandinavian tradition uses the same wood all the way through. Thermal modification runs this aspen through extreme heat and steam, no chemicals ever, and changes it at a cellular level so it can’t hold moisture. It won’t expand, contract, cup, or rot in the conditions of a sauna. The golden-brown color runs all the way through the piece, so a cross-cut end matches the face and nothing looks patchy after you trim to length.
One honest note: the thermal process does reduce some mechanical strength compared to raw aspen. It’s more than adequate for bench framing at normal spans, but it’s not a structural beam. Size your supports appropriately and you’ll have no issues. If you have questions about span and spacing, text us before you order.
Specifications
- SKU: PS-THERMO-ASPEN-3X3-S4SEE-SHP
- Species: Thermally modified aspen (glulam engineered)
- Profile: S4SEE SHP bench board
- Thickness: 2.68″
- Width: 2.68″
- Available lengths: 1 ft, 8 ft
- Price: $11.62 per linear foot (MAP)
- Made in: Estonia
Where it goes
Bench legs, cross-supports under bench decking, and structural skirting framing. Order alongside the thermo-aspen 2×3 or 2×6 bench boards and the whole bench system ships and arrives together. The matching wood tone means no awkward color breaks between support and seat.
Shipping and samples
Sold by the linear foot. Shipping is a flat $795 to the continental US, or free when you order with a heater. We send free samples so you can confirm the color and weight in person before committing to a full order. Text your name and address to (844) 565-1113 and we’ll send them out.
Call Ben² at (844) 565-1113 if you’d like to talk through the board count before you order.

Prebuilt
Sauna Brushes
Vents