Thermo-Spruce
Ask us which bench board to reach for and Thermo-Spruce comes up fast. Take Nordic spruce, bake it near 400°F until the moisture and the sap cook out, and you are left with a thicker, denser board that holds its shape, sheds water, and will not weep pitch onto the back of your legs. That last part is the whole reason it earns a spot on the bench, where plain spruce never could.
The heat treatment darkens the pale wood to a soft amber and keeps the light, even Scandinavian grain that suits a clean modern build. It pulls triple duty: tongue-and-groove STS4 cladding for walls and ceiling, 5/4 SHP for benches and floor, and 2×6 S4SEE bench, backrest, and skirting stock milled with eased edges. There is even a brushed-and-waxed black profile if you want the walls to recede and the heater to be the thing you see.
This is part of why we went big on thermally modified wood across the whole shop: it does outdoors and indoors, season after season, what untreated boards only manage for a while. If you are weighing thermo-spruce against thermo-aspen or alder for your seats, call us at (844) 565-1113 and we will tell you which one fits your room and your budget.
*Free samples available! Select ‘sample’ and ‘free shipping for samples’ under any wood profile.
*Most wood orders qualify for free shipping with any heater purchase.
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PROSAUNAS Thermo-Spruce 2X4 S4SEE SHP Bench, Backrest & Skirting – Sauna Wood
Price range: $4.56 through $45.60Ben sided his own house in thermo-spruce. That tells you something. This is the 2×4 bench board in thermally modified Nordic spruce, 1.02″ thick by 3.54″ wide, and it’s the budget-friendly bench, backrest, and skirting board. Rich amber color, tight knots, a rustic look that’s not for everybody but that a lot of people flat-out love. The thermal modification (heat and steam, no chemicals) gives it the same moisture resistance and stability you get in thermo-aspen, at a lower entry price. Strong, rot-resistant, and good for benches, backrests, and skirting. The classic move is thermo-spruce walls with thermo-aspen benches. Sold by the linear foot.
1X4 Black Thermo-Spruce STS4 T&G Wall Cladding – Brushed & Waxed Black Sauna Wood by Thermory
Price range: $4.27 through $251.00The Bold New Statement in Sauna Design
Introducing Black Thermo-Spruce – the dramatic, sophisticated sauna wood that’s revolutionizing modern sauna aesthetics. This isn’t paint or stain; it’s the natural beauty of spruce transformed through Thermory’s intensive thermal modification process, creating a rich, deep black that’s as durable as it is stunning.
Wire-brushed to perfection, each board reveals the natural grain patterns that make every installation unique. The textured surface doesn’t just look incredible – it feels amazing under your fingertips, adding a tactile dimension to your sauna experience. Finally, a true black sauna wood at a price that makes sense.
Thermo-Spruce Sauna Bench and Floor Wood – 5/4 SHP Sauna Wood By Thermory
Price range: $5.55 through $222.00One of our missions at Sauna Marketplace is to make it more affordable to build a DIY sauna without compromise. Sauna bench wood has always been a barrier, but this 5/4 SHP Bench profile from Thermory makes it easier than ever.
Intense natural modification using heat and steam alters this Nordic Spruce at a cellular level, resulting in a more durable and healthy choice than Western Red Cedar at a fraction of the price. Unlike WRC, this Thermo-Spruce won’t warp, expand, contract, or cup.
Recommended Uses: Sauna benches, backrests, flooring, and skirting. These 1.0″ thick sauna bench boards are thick enough to build the frame, but we recommend using standard 2x4s for that. See detail below.
1X4 Thermo-Spruce STS4 T&G Wall Cladding – Thermally Modified Sauna Wood by Thermory
Price range: $2.50 through $150.00Thermo-Spruce 1×4 by Thermory is the most affordable way to achieve beautiful thermally modified wood walls in your sauna. Popular in Finland for it’s thermal performance, Nordic Spruce is also a sustainable choice. We love the rustic look and unique, tight knots that look like wings. Thermo-Spruce gives a pleasant, mild aroma with far lower VOC content than Western Red Cedar. Natural thermal modification changes the wood at a cellular level to resist rot, decay, warping, and cupping.
Actual wall coverage is 3.1″ to 3.2″, depending on installation. Thermo-Spruce pairs well with Thermo-Aspen benches.
PROSAUNAS Thermo-Spruce 1X4 T&G STS4 Wall Cladding – Sauna Wood
Price range: $2.35 through $32.96The most economical real sauna wood we carry, and the traditional one. Natural Nordic Thermo-Spruce, 1×4 smooth tongue-and-groove, the wood Finland has lined saunas with for generations. Light tone, tight characterful knots, a clean mild scent. It is not thermally modified, so it moves a little more than our thermo woods through the heat-and-cool cycle. We carry it for the budget build and the honest Finnish look. Sold by the linear foot, in lengths up to 14 ft.
PROSAUNAS Thermo-Spruce 2X6 S4SEE SHP Bench, Backrest & Skirting – Sauna Wood
Price range: $5.87 through $58.73Ben sided his own house in thermo-spruce. That tells you something. This is the 2×6 bench board in thermally modified Nordic spruce, 1.02″ thick by 5.51″ wide, and it’s the classic budget build starting point. Rich amber color, tight knots, a rustic look that’s not for everybody but that a lot of people flat-out love. The thermal modification (heat and steam, no chemicals) gives it the same moisture resistance and stability you get in thermo-aspen, at a lower entry price. Strong, rot-resistant, and good for benches and floors. The classic move is thermo-spruce walls with thermo-aspen benches. Sold by the linear foot.
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