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The Pine That’s Perfect for Exterior Applications



How do you thermally modify wood?

How do you make softwood pine a great option for exterior projects like decks and siding? Believe it or not, heat and steam. It sounds crazy, but there is real science behind it.

The process is called Thermal Modification and it is a chemical-free method of heat-treating wood, using only high temperatures and steam to increase wood’s durability, water repellency, insect and rot resistance, and dimensional stability.

Developed in Finland, and used commercially in Europe since the 1990s, the process is now being utilized for a new lumber product called Pakari here in the U.S.

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Pakari’s process begins with plantation-grown Radiata Pine that is FSC-certified. It is heated to 500°F, dropping the woods moisture content to nearly zero. The chemical and structural changes that occur in the wood at high temperatures are what give the wood more stability and its resistance to the elements.

Once those important changes have occurred, steam is introduced into the kiln to return moisture content to between 6-7%. The entire process takes approximately 65 hours, and results in a product with an exotic wood look that is perfect for building decks and siding, and even interior projects like paneling.

Manufactured in Chico, CA and gaining in popularity in that region, Pakari came to Colorado in 2020. Sears Trostel Lumber & Millwork in Fort Collins now stocks Pakari decking, lumber and siding, as well as manufactures custom siding and paneling profiles.

Recent Pakari Projects

Pakari is a great choice for building decks. Chet Nance, Sears Trostel’s retail store manager, was already investigating decking options for his home when Pakari came into stock at the store. Soon after, he and his wife decided that Pakari was a good choice for them.

“We looked at the other options that were out there,” Chet said. “Redwood was hard to get and Cedar was nowhere to be found at the time. We looked at composites, but heard stories of sway in deck boards. What solved it for us was on a hot day we went out on a composite deck and took our shoes off, and it was extremely hot. We did the same thing with Pakari boards and guess what? It was nice and cool…not hot at all.”

With that, the rich brown color of Pakari, and the fact that it is real wood, they were sold. Chet went to work on sourcing the framing materials for the deck and finding a contractor to install it.

pine decks siding

“I decided to not go with treated lumber. Instead, we went with a metal frame with a 25-year warranty from Fortress®, and it worked out really well,” Chet said. The pricing at that time was about 40% higher than it would have been with a wood frame. But, with the warranty and not ever having to replace it, it was well worth it. Today, they are about equal because of the price of lumber.”

The Nance’s deck was completed in August 2020. “I’ve not seen a deck that was so easy to put together…it worked out tremendous,” Chet said about working with the Pakari and the metal framing.

Another Pakari deck project was recently completed in May at the home of Pete Weber & Jill Handwerk in Fort Collins. The sustainability and environmentally friendly characteristics are what most appealed to them about using Pakari. David Weiss designed and built the deck, and this was his first time to work with Pakari. He has built homes and decks since 1992.

“It installed great,” when asked how it was to work with Pakari. “You can work with it well, you can bend it, and it looks nice.” He was also impressed at how easy it is to handle the product. “It’s lightweight and the boards are straight.”

Pakari decking is available with smooth and ribbed surfaces. The customer wanted the ribbed surface, which David wasn’t sure about at first. “It’s unusual to have wood that the grooves would actually line up. But it looks consistent, uniform the whole way around.”

Pakari deck

“When you look at it, the product kind of speaks for itself,” he said. “I wasn’t sure what it was going to look like, but to me it looks wonderful. It’s a nice-looking deck.”

Working with Pakari

Thermal Modification increases durability and stability of the wood, as well as reduces the wood’s ability to absorb water. The resulting product does not shrink or swell to the same degree as unmodified wood and is less susceptible to rot. Even with these improvements, it is important to remember that Pakari is a softwood, like redwood and cedar, and can dent, scratch and check.

To keep Pakari in optimal condition it’s recommended that it is given the same care and maintenance as other unmodified wood products. While its ability to shrink and swell is decreased, it will still move slightly. To minimize this, it is recommended to apply one coat of finish to all surfaces of the wood prior to installation.

The Thermal Modification process turns the wood a rich chocolate brown color that is normally only seen in exotic hardwoods. But if left unfinished in direct sunlight – especially at the altitude and intensity we experience the sun in Colorado – Pakari will weather to a natural silver patina. To help preserve the original color, it is necessary to finish Pakari with a UV protectant.

Pakari is not intended to be used for structural components, such as joists, beams, support posts, columns or other load-bearing applications. Any deck built with Pakari must be framed with a code-compliant material.

Not manufactured for direct ground contact, Pakari is best installed at least 12-18” above ground in decking applications.

Pakari works well with standard woodworking tools, but it is recommended that all blades and routers have carbide tips.

Stainless steel fasteners or epoxy-coated screws, such as HULK™ Self-Drilling Surface Mount Epoxy-Coated Steel Screws, should be used to avoid mineral staining. Screws are recommended when installing Pakari, due to the increased brittleness of all thermally modified wood. Pre-drilling is also suggested. All fasteners should be applied a minimum of 5/8” from board edge and a minimum of 1” from board ends.

pine decks siding

We recommend that deck boards be spaced with 3/16″ to 1/4″ gap between them. Pakari will not shrink or swell to the same degree as unmodified wood, but correct spacing between boards is still important to allow for proper airflow beneath the deck. A larger gap creates better airflow.

Coatings are not necessary with Pakari to protect the wood from decay. But like any wood product, if left untreated, Pakari will weather. To help protect it from the weathering process, a high-quality sealant with UV protection should be applied. This will help protect against unwanted check and help maintain the original color. As mentioned earlier, applying one coat of finish on all surfaces prior to installation is recommended. Applying a second coat after installation, and refinishing every one to two years thereafter, will provide further protection and produce the best results.

Pakari is a durable, water and decay resistant, chemical-free, and sustainably sourced wood product that is ideal for decking, siding and paneling projects. It is in good supply compared to other exterior woods currently experiencing supply issues, such as Cedar. It may just be the ‘greenest’ lumber resource on the market.

For additional information, contact Sears Trostel at 970-482-1928 or [email protected].


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