Made from Carbon Smart Wood™ — premium thermally modified or naturally durable lumber from Cambium Carbon's nationwide salvage and milling network.

About Thermal Poplar

Thermal Poplar is North American yellow poplar transformed through a high-temperature thermal modification process. The wood is heated to 380–430°F in an oxygen-controlled chamber, fundamentally changing its cell structure. The result: a rot- and decay-resistant softwood with dramatically improved dimensional stability and a rich, chocolate-brown tone throughout.

No chemicals are added — only heat and steam. The process produces a dimensionally stable, biologically durable wood ideal for sauna interiors, exterior cladding, and outdoor applications where you want hardwood performance without the cost or weight.

Nickel Gap Profile

Tongue-and-groove milling with a uniform ~1/8" reveal between boards (about the thickness of a U.S. nickel). Self-spacing for clean, fast installation and a modern, evenly-spaced shadow line. A favorite profile for sauna interiors and high-design feature walls.

Modern Nickel Gap Wall Cladding

Tongue-and-groove (Nickel Gap profile) milled cladding for sauna interiors, accent walls, exterior siding, and ceiling applications. Self-spacing installation gives a fast, consistent result every time.

Minimum Order Quantity

Lumber orders require a minimum of 100 boards total — any combination of Bench & Floor Boards and Wall Cladding boards counts toward the minimum. Mix species, sizes, and lengths freely; only the combined board count matters.

Why the minimum? Lumber ships LTL (Less-Than-Truckload) freight with oversize-package handling, so we strongly recommend ordering your complete sauna package — heater, controls, door, lumber, and accessories — in a single shipment. When wood ships separately from the rest of your sauna components, you frequently incur hundreds of dollars in additional freight charges that we can't absorb.

Not sure how much material your project needs? Contact us for a free takeoff based on your sauna's size, layout, and species selection — we'll line everything up to ship together.

Lengths & Custom Quotes

Standard lengths shown are 4 ft through 10 ft. Material is sourced in random widths and random lengths from the kiln, so specific-length orders may carry a 15–20% surcharge and extended lead time. Need 12 ft, 14 ft, or longer? Contact us for a custom quote and we'll source it for you.

Care & Finishing

For exterior applications we recommend pre-finishing with CUTEK® Extreme at the time of milling for the most consistent absorption and longest-lasting protection (available on the Specialty Exterior Finish page). For sauna interiors, most species are left unfinished or treated with a sauna-safe oil.

Every Board Has a Story

This material is part of the Carbon Smart Wood™ program — sustainably sourced from trees diverted from development sites, storm-felled stands, and natural decline. Wood that would otherwise have been chipped, burned, or sent to landfill is salvaged, milled, and given a second life.

• 26% less CO₂e than conventional wood, and 7× less than wood-plastic composites.
• 4 trees protected in standing forests for every 1,000 board feet of Carbon Smart Wood™ used.
• 20% lower transportation emissions through domestic sourcing and regional mill hubs.
• 15% of every sale reinvested into urban forest stewardship and tree-canopy restoration.
• 5 million+ board feet diverted from the waste stream — and counting.

Sourced and milled 100% domestically by Cambium Carbon's nationwide partner network, supporting American manufacturing jobs and green-collar career pathways.

Sustainability Certifications & Affiliations

• One Percent for the Planet member
• Declare label / ILFI Living Building Challenge compliant
• Sustainable Furnishings Council member
• World Economic Forum UpLink Top Innovator