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Thermally Modified Siding

Premium thermally modified siding boards for residential and commercial projects

Janka

Varies by species

Density

10-15% lighter

Fire Rating

Class B

Durability

20+ years

Origin

Various

Color

Rich brown

Overview

Thermally modified wood siding is created by heating wood to 400°F+ in a controlled, oxygen-free environment. This chemical-free process permanently alters the wood's cellular structure, delivering enhanced decay resistance, improved dimensional stability, and a rich, consistent brown color throughout the board. Available in species like ash, pine, and poplar, thermally modified siding is an eco-friendly alternative to tropical hardwoods and chemically treated lumber — offering comparable durability without environmental compromise.

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Learn more about this wood species on our Thermally Modified wood guide.

Benefits of Thermally Modified Siding

Chemical-free modification process — no toxins or preservatives

Enhanced decay and insect resistance (Class 1-2 durability)

20+ year lifespan for exterior siding

Improved dimensional stability — less shrinking and swelling

Rich, consistent brown color throughout the board

Reduced moisture absorption (4-6% EMC vs 12%+ for untreated)

Eco-friendly and sustainable

Available in multiple species and profiles

Sizes Available

1x6 Shiplap

1x6 T&G Siding

1x4 Shiplap

1x6 Channel Siding

1x6 Bevel Siding

Rainscreen profiles

Custom profiles available

Custom sizes and lengths available. Request a custom quote.

Installation Tips

Pre-drill near board ends to prevent splitting — thermally modified wood is more brittle.

Use stainless steel fasteners.

Install over a ventilated rainscreen system for best performance.

Handle with care — boards are lighter and more brittle than untreated wood.

Standard woodworking tools work well.

Apply a UV-protective oil or stain to maintain the brown color.

Maintenance

Apply a UV-protective oil or stain annually to maintain the rich brown color. Without UV protection, thermally modified wood will weather to silver-gray — the durability is unaffected either way. The reduced moisture content means coatings adhere well and last longer. No toxic chemicals to worry about during maintenance. Simply clean with mild soap and water as needed.