How do you make thermally modified wood?

Thermally modified wood starts off as untreated lumber that is cut to size at a sawmill. It’s brought to a chamber where it is slowly heated to 212 degrees Fahrenheit. This process dries it to nearly 0% moisture content. The wood is then “cooked” at temperatures over 400 degrees Fahrenheit for several hours. At this stage, organic matter is totally removed so the wood will not be a feeding ground for insects, mold, and fungus. Lastly, the wood is cooled and moisture is added to around 6% - 7% moisture content. The thermally modified wood is more durable than its original form and shrinking and swelling are reduced by 50% - 90%.

What’s the difference between kiln-dried wood and thermally modified wood?

Thermally modified wood is structurally very different from its original, untreated form. The high temperatures make it more durable, water-resistant, and resistant to pests and pathogens. Kiln-dried wood is the industry standard for artificially drying wood before it goes to market. The wood is subjected to temperatures of 140 degrees Fahrenheit but the wood’s composition does not change.

What’s the difference between heat-treated wood and thermally modified wood?

“Heat-treated wood” and “thermally modified wood” are sometimes used interchangeably, but they are different in practice. Thermally modified wood is a modern technology that heats the wood at temperatures over 400 degrees Fahrenheit with a goal of achieving a moisture content of 0%. The process changes the biological nature of the wood to achieve several features such as durability, bendability, and resistance to rot, insects, and fungus. Heat-treated wood is a certification required to ship wood internationally. The wood is heated to an internal temperature of 132.8 degrees Fahrenheit for at least 30 minutes. The process kills organisms like insects and fungi, for the purposes of stability and reducing the likelihood that foreign pathogens will travel internationally. It’s also known as Phyto Certification.

Can thermally modified wood be used outdoors?

Yes, thermally modified wood is a great choice for outdoor projects like decking. It naturally resists moisture and won’t crack or warp even after years of rain and harsh weather. Under reasonable conditions, a thermally modified wood deck will last for 30 years. Thermally modified wood decking will turn gray after a few years or even months. Its color can be restored by treating it with a non-toxic, high-performance wood protector with a UV inhibitor and tint.

Is thermally modified wood the same as pressure-treated wood?

No, thermally modified wood and pressure-treated wood are very different. Pressure-treated wood is infused with chemical preservatives that protect the wood from insects and rot. It’s placed in a pressurized tank that removes the air and replaces it with chromated copper arsenic (CCA). In 2003, the EPA agreed that toxic CCA-treated wood cannot be used in residential structures like decks, picnic tables, playground equipment, and fences.

How long does thermally modified wood decking last?

A thermally modified wood deck is often guaranteed for up to 30 years. With proper care, the deck should be resistant to weather, insects, rot, and fungus. The thermally modified wood deck will turn gray eventually, at which point it can be treated with a non-toxic, high-performance wood protector with a UV inhibitor and tint.

Does thermally modified wood rot?

Thermally modified wood is naturally resistant to rot without the need for added chemicals. Decaying fungi that cause rot thrive in wet environments, so the low moisture content of thermally modified wood makes it a natural choice for outdoor projects.

Is thermally modified wood decking resistant to termites and insects?

Thermally modified wood decking is naturally resistant to most insects (including termites), without the need for added chemicals. Thermally modified wood resists the presence of organisms on which insects feed, making it an unlikely setting for infestation and feeding.

How much does thermally modified decking cost?

When pricing a thermally modified wood deck, a homeowner can expect to spend about $8 to $10 per sq. ft. Compare to about $5 to $8 for pressure-treated wood and $9 to $15 for composite decking. Pricing is for material only, not including installation. As a relatively new product, thermally modified wood is available direct from manufacturers and specialty suppliers.

In-Depth Product Guide

Thermally Modified Wood Decking

FAQs

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Thermally modified decking is decking made of wood that has been heated to 400°F (180 °C) in the absence of oxygen, a process called pyrolysis. This process changes the chemical structure of cell walls, comprised of cellulose, hemicellulose, and lignin. What you get is a wood product that is naturally durable and resistant to water, insects, mold, and decay.

Thermally modified decking is weather-resistant and generally lasts up to 30 years, while decking made from pressure-treated wood can erode metal and lose stability. Thermally modified wood is a non-toxic alternative to lumber that is commonly treated with chemical preservatives that emit volatile organic compounds.

Thermally modified wood stands up to changes in temperature and moisture better than other types of wood decking. If properly maintained, thermally modified decking won’t lose structural integrity due to rotting or warping. Unsealed or unfinished thermally modified wood loses its color (grays) more quickly than other types of wood, so be sure to check the product specs before buying. Your deck’s color can be restored and preserved by treating it with an oil-based preservative. Look for a non-toxic, high-performance wood protector with a UV inhibitor and tint, if desired. A thermally modified wood deck should be sealed every 3-5 years.

Thermally modified wood is a non-toxic wood alternative to pressure-treated wood. You can feel good about your family interacting with a chemical-free deck or swing set made of thermally modified wood. Its moisture resistance and durability make it an attractive alternative to composite decking for homeowners who prefer to avoid plastic.

Thermal modification technology is used in the guitar-making industry. The process, often called “roasted” “Thermo curing” or “baked”, prevents warping and cracking along the soundboard and fretboard. Some musicians also find that the process helps new acoustic guitars sound “well broken in”.

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