A poolside hardwood deck made from Mataverde thermally modified wood.

Thermally Modified Wood

Mataverde thermally modified wood logo

What is Thermally Modified Wood?

Mataverde thermally modified wood begins as a standard kiln-dried wood species. Using a precise scientific heating process under pressure, the wood undergoes a transformation that enhances its performance, stability, and durability.
During the thermal modification process, the wood is "cooked," removing acids and sugars. This eliminates the primary food source for mold and insects, making thermally modified wood significantly more insect-resistant and rot-resistant compared to its original form.
Mataverde ThermaWood is available in various high-performance options:
  • 5/4 x 6 Decking
  • Tongue and Groove (T&G) Siding
  • Wood Rainscreen Siding
For areas prone to wildfires, Mataverde ThermaWood FR is a thermally modified fire-retardant wood that is non-toxic and ignition-resistant, ideal for high fire hazard zones.
 
Explore our full range of thermally modified wood siding and decking options:
 

Why Use Thermally Modified Wood for Your Outdoor Projects?  

Superior Stability

Thermally modified wood is remarkably stable, meaning minimal movement over time. While all wood expands and contracts with moisture, thermally modified wood exhibits significantly less shrinkage and expansion compared to non-modified woods, ensuring a long-lasting, reliable material.

Unmatched Durability

The thermal modification process alters the wood at the cellular level, making it resistant to rot and undesirable to insects. This increases its lifespan, making it a cost-effective choice for exterior applications.

Sustainable and Local

Thermal modification enhances the performance of Western Hemlock and other sustainably harvested North American wood species, allowing them to rival tropical hardwoods without harming rainforests.

100% Natural & Chemical-Free

The best thermal modification methods use only heat and pressure—no chemicals, no toxins. This creates a high-performance, eco-friendly material suitable for decking, siding, and architectural applications.
Whether you’re designing a stunning deck, recladding a building, or creating an award-winning architectural masterpiece, Mataverde ThermaWood offers a superior, reliable solution.
 
 
 

What Makes Thermally Modified Wood Stand Apart?

Many different processes and wood species have been tested over the years, but not all thermally modified wood products perform equally. Mataverde ThermaWood is created using an advanced Danish autoclave "vacuum" kiln, which modifies the wood using high temperatures and pressure while consuming far less energy than traditional methods.

A luxurious house exterior made from thermally modified Western Hemlock siding and decking material from Mataverde Decking.ThermaWood Hemlock siding, trim and decking is naturally beautiful

This gentle yet effective process reduces the likelihood of cracks, splits, or checks, leading to less waste at job sites. Plus, because it’s all-natural and chemical-free, ThermaWood is an excellent choice for environmentally conscious builders and homeowners.

 

The Beauty of Mataverde ThermaWood Hem-Fir: Color, Graining, and Grading

 

When Western Hemlock undergoes the ThermaWood process, its appearance transforms beautifully. The modified wood takes on a richer, darker hue with reduced color variation, resembling the warm tones of Western Red Cedar—a favorite for its natural aesthetic appeal.

A sample of typical color variations in Mataverde's Thermawood Hem Fir fire retardant siding material.

 

Mataverde ThermaWood Hem-Fir Grading

  • A & Better Grade: Features clear vertical grain with minimal knots, creating a refined look. Some mineral streaking occurs, adding natural character.
  • C & Better Grade: A more rustic aesthetic with mixed grain, flat sawn boards, and some secure knots. Mineral streaking is more pronounced.

For aesthetic flexibility, sections of boards that don’t meet your visual preferences can be trimmed to create a seamless, stunning final project.

 
 

Exceptional Physical Properties of Mataverde Thermally Modified Hemlock Wood

 

Highly Durable

  • Thermally modified wood resists fungi and insects due to its transformed cellular structure.
  • The process makes wood cells nearly airtight, preventing moisture penetration and decay.

Superior Strength

Unlike many thermally modified woods that become brittle, ThermaWood Hem-Fir actually gains strength. With a modulus of rupture of 12,693 psi, it withstands over 6 tons of pressure per square inch before bending to the breaking point.

Extreme Dimensional Stability

Thermally modified Western Hemlock expands and contracts minimally, ensuring long-term stability. Tests show an average dimensional change of just 5.62% with moisture fluctuations, making it an outstanding choice for exterior applications.

(Data courtesy of the University of Idaho and the University of Minnesota.)

Thermally Modified Wood Pros and Cons

Pros:

  • ✅ Superior Stability – Less expansion/contraction than untreated wood.
  • ✅ Increased Durability – More resistant to rot, mold, and insects.
  • ✅ Enhanced Appearance – Richer tones, reduced color variation.
  • ✅ Sustainable & Eco-Friendly – Local, chemical-free alternative to tropical hardwoods.
  • ✅ Better Performance – Less warping, splitting, and cracking.
  • ✅ Cost-Effective in the Long Run – Longer lifespan reduces replacement costs.

Cons:

  • 🔸 Slightly Higher Upfront Cost – While the initial price is higher than untreated wood, it pays off in longevity and reduced maintenance.
  • 🔸 Darkening Over Time – Exposure to sunlight can further darken thermally modified wood, though this can be managed with UV-protective finishes.
  • 🔸 Slightly More Brittle Than Non-Modified Wood – The ThermaWood process actually strengthens the wood compared to other thermal modification methods. Other thermal modification techniques make the wood more brittle than the original wood. Careful handling is required.
 

Interested in discovering more about Mataverde ThermaWood siding and decking options? Check out the pages below for additional details:

 
 
 

Mataverde ThermaWood Decking

 

Interested in decking? Explore our top-quality options from the best thermally modified wood suppliers:

 

DISCOVER MATAVERDE THERMAWOOD HEM FIR DECKING HERE

 

Mataverde ThermaWood Siding

Ready to enhance your property with thermally modified wood siding?

 

THERMAWOOD HEM FIR RAINSCREEN SIDING INFO

 
 
 

Mataverde ThermaWood FR Hem-Fir Decking and Siding

Mataverde Thermawood Hem-Fir is also available with a fire retardant treatment for decking, siding and lumber.
ThermaWood FR uses an environmentally friendly, non-toxic formula applied under pressure that lasts outdoors indefinitely under the worst weather conditions.