Thermally Modified Wood
What is Thermally Modified Wood?
Thermally Modified wood is wood that has undergone a specialized process in which it is heated with steam to temperatures of approximately 400–410°F. This process transforms the wood at the molecular level, creating a highly durable material that is ideal for outdoor applications.
During the modification process, the wood's cell walls become permanently stabilized, making the wood much more resistant to water absorption than untreated wood.
One of the greatest advantages of Thermally Modified wood is its exceptional durability, providing an outdoor lifespan of 25 years or more. The process uses only heat and steam, without chemicals or preservatives, making it an environmentally friendly choice. Thermowood® by Arbor Wood Co. is sustainably sourced from responsibly managed Indiana farmland, offering a renewable and environmentally conscious building material.
Cladding
Arbor Wood Co. thermally modified wood cladding is crafted from domestically sourced, sustainably harvested timber and engineered for exceptional exterior performance. Through a chemical-free thermal modification process using only heat and steam, wood species not naturally suited for outdoor applications gain enhanced durability, dimensional stability, and resistance to moisture, rot, and fungal decay. Available in premium Ash, Poplar, and Pine, Arbor Wood cladding can be finished in a range of sophisticated tones, including Clear Oil, Iron, Sand, Stone, Quartz, and Onyx, as well as striking Burned Pine and Burned & Brushed finishes in Coal, Carbon, and Mineral. Combining natural beauty, long-lasting performance, and sustainable sourcing, Arbor Wood is an ideal cladding solution for residential and commercial projects alike.
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Decking
Arbor Wood Co. thermally modified decking combines the natural beauty of real wood with the durability needed for long-lasting outdoor performance. Made from domestically sourced, sustainably harvested Ash and Pine, the decking undergoes a chemical-free thermal modification process using only heat and steam. This enhances dimensional stability, reduces water absorption, and improves resistance to rot, decay, and fungal growth, creating a sustainable alternative to composite, pressure-treated, and tropical hardwood decking.
Designed for both beauty and performance, Arbor Wood decking offers rich, natural tones, exceptional workability, and long-term stability with minimal expansion and contraction. Available in grooved and non-grooved profiles, it can be finished with UV-protective oils or coatings to preserve its original color, or left unfinished to naturally weather to an elegant silver-gray patina over time.
| Nominal Size | Net Size | Length | Profiles | Species | Grade | Recommended Clips |
|---|---|---|---|---|---|---|
| 1 x 6 | 0.75" x 5.50" | 6'-12' Long | Groove & Groove / Eased 4 Edge / With or Without Structural End Match | Thermally Modified Pine, Ash, or Popular | Prime Grade | DeckWise® / ThermoClip™ |
| 5/4 x 6 | 1.00" x 5.50" | 6'-12' Long | Groove & Groove / Eased 4 Edge / With or Without Structural End Match | Thermally Modified Pine, Ash, or Popular | Prime Grade | DeckWise® / ThermoClip™ |
Species
Pine: Southern Yellow Pine is valued for its distinctive grain pattern, natural warmth, and versatility. When thermally modified, it gains improved dimensional stability and resistance to moisture, rot, and fungal decay, making it a durable and attractive choice for decking, cladding, and other exterior applications.
Poplar: Tulip Poplar is one of North America's tallest hardwoods and is valued for its versatility and stability. Thermally modified Poplar provides a lightweight, durable option with a clean, contemporary appearance.
Ash: American White Ash is known for its outstanding strength, flexibility, and smooth grain. Long used for baseball bats, hockey sticks, and fine furniture, thermally modified Ash delivers exceptional durability with a refined, modern look.
Installation Tips
- Use Stainless Steel Fasteners: Always use high-grade stainless steel screws or nails to prevent rust, corrosion, and staining over time.
- Pre-Drill Fastener Holes: Thermally Modified Hardwood should always be pre-drilled before installing screws or nails to help ensure a clean, secure installation.
- Maintain Proper Ventilation: Install siding as a rainscreen system with adequate airflow behind the boards to promote drainage and long-term performance.
- Protect the Finish: To maintain the wood's rich color, apply a penetrating UV protectant such as Cutek Extreme. Reapply every six months during the first few years, or allow the wood to naturally weather to an attractive silver-gray patina.
Frequently Asked Questions
What is thermally modified wood?
Thermally modified wood is natural hardwood that has been heated with steam to approximately 400–410°F. This specialized process changes the wood at the molecular level, stabilizing its cell structure and reducing its ability to absorb moisture. The result is a durable, dimensionally stable wood product that is well suited for outdoor applications such as decking, siding, and rainscreen systems.
Are chemicals used to make thermally modified wood?
No. Thermowood® by Arbor Wood Co. is produced using only heat, steam, and time. No chemical preservatives are added during the modification process, making it a natural and environmentally responsible alternative to chemically treated lumber.
How long does thermally modified wood last outdoors?
Thermowood® by Arbor Wood Co. has a Class 1 durability rating and an expected outdoor lifespan of 25 years or more. Proper installation, ventilation, care, and environmental conditions can all contribute to the product’s long-term performance.
Does thermally modified wood need to be pre-drilled?
Yes. Thermally modified hardwood should be pre-drilled before installing screws or nails. Pre-drilling helps prevent splitting and creates a cleaner, more secure installation.
Evergreen Forest Products also recommends using high-grade stainless steel fasteners. Stainless steel helps prevent rust, corrosion, oxidation stains, and discoloration around the fastener locations.
Can thermally modified wood check or crack?
As with any natural wood product, thermally modified boards may develop small, superficial checks as the wood adjusts to the moisture conditions of its environment. Minor surface checking is a natural characteristic of real wood and does not necessarily indicate a problem with the product.
Applying a penetrating wood oil or protectant, such as Cutek Extreme, may help minimize checking while protecting the appearance of the wood.
What maintenance does thermally modified wood require?
Thermally modified wood is relatively low maintenance. Occasional cleaning can help remove dirt, pollen, mildew, and other surface buildup.
You can choose between two appearance options:
* Apply a penetrating UV protectant to help preserve the wood’s warm, rich color.
* Leave the wood untreated and allow it to naturally weather to an attractive silver-gray patina.
When maintaining the original color, follow the finish manufacturer’s application instructions. During the first few years, the UV protectant may need to be reapplied approximately every six months, depending on sun exposure, weather conditions, and the application.
How much spacing is required between thermally modified deck boards?
Thermally modified deck boards should be installed with a minimum spacing of ¼ inch between boards. The decking should also be installed at least 12 inches above the ground with proper ventilation underneath.
Adequate spacing and airflow allow water to drain, help moisture evaporate, and support the long-term performance of the decking. Always follow the current installation guide and applicable building requirements for your specific project.
Is thermally modified wood sustainably sourced?
Yes. Thermowood® by Arbor Wood Co. is produced from natural Pine, Ash, and Poplar sourced from responsibly managed forests in Indiana. The thermal modification process does not require chemical preservatives, plastics, or synthetic additives.
FSC-certified options may also be available. Contact Evergreen Forest Products to discuss current species, profiles, certifications, and product availability for your project.
