ThermaPro Wood vs. Black Locust
- Thermapro
- 4 days ago
- 4 min read
A few weeks ago, I had the chance to visit an animal sanctuary tucked deep in a South Florida swamp. Naturally, my passion for thermally modified wood had me eyeing the details of the several-mile-long wooden boardwalk winding through the wetlands. It wasn’t in the best shape, so—curiosity got the better of me—I dug a little deeper to find out why.
I found that the boardwalk was made of Black Locust—chosen for its natural durability and eco-friendly properties, which help protect the sensitive wetland environment. But as I walked along the twisted, cracked, and creaky planks, I couldn’t help but think: there has to be a better option. My guess? They haven’t discovered thermally modified wood yet. And just like that, another blog post idea was born - Black Locust VS Thermally Modified Wood.
Since the majority of ThermaPro Wood Decking that we produce is made from Southern Yellow Pine, due to its exceptional property/price ratio, let’s compare SYP thermally modified boards to black locust boards.
Durability & Longevity: Black Locust is naturally rot-resistant and can last up to 50 years in outdoor applications. Similarly, thermally modified Southern Yellow Pine (SYP) offers the same level of rot resistance and longevity with the added benefit of being insect and fungi resistant.
Sustainable & Renewable: Both Black Locust and Southern Yellow Pine are fast-growing, renewable resources that are grown domestically. While many thermally modified brands are imported, ThermaPro Wood is made right here in the USA. Since neither wood is treated with chemicals, they can be safely recycled or composted at the end of their life cycle—making them smart, sustainable choices for environmentally conscious projects.
Eco-Friendly: Thermal modification is a chemical-free process that uses only heat, steam, and pressure to alter the wood’s cell structure—eliminating its ability to bond with water (H₂O). The result is enhanced durability and stability without any added chemicals. Like Black Locust, ThermaPro Decking is an all-natural, eco-friendly material—but with greater resistance to warping, twisting, and cracking.
However, that’s where the similarities end.
Dimensional Consistency: Wood is naturally hygroscopic, meaning it absorbs moisture from its environment. This water absorption leads to expansion and contraction—causing common issues like twisting, warping, and cracking. During thermal modification, key cellular changes take place, including the removal of hydroxyl groups that typically bond with water molecules. As a result, thermally modified wood becomes hydrophobic and resists water absorption, which means no expansion, no contraction, and far greater dimensional stability. Black Locust, by contrast, is well known for twisting and warping when exposed to the elements.
Installation & Fastening: Both materials work best with pre-drilling and stainless-steel fasteners. However, Black Locust decks using hidden fasteners are prone to sideways movement. Over time, this will result in a crooked deck or walkway. Thermally modified wood resists movement, so hidden fasteners produce a long-lasting, beautiful deck.
Aging Gracefully: Black Locust and untreated modified Southern Yellow Pine naturally weather to a silver patina over time. However, thermally modified Southern Yellow Pine offers a clear advantage—it retains its shape and structural integrity without the twisting, cupping, or cracking that Black Locust is often known for. The difference lies in the thermal modification process, which enhances durability while delivering superior dimensional stability and a cleaner, more refined finish.
Aged Black Locust Boardwalk by Fred Myers Aged Thermally Modified Wood Dock
Price: Black Locust is a premium wood with a price tag to match—often comparable to Ipe and other exotic hardwoods. In contrast, ThermaPro Wood is domestically produced, making it one of the most cost-effective thermally modified products on the market. On average, Black Locust costs nearly three times more than ThermaPro Wood’s Southern Yellow Pine Decking, making ThermaPro Wood a smarter, budget-friendly choice without compromising on performance or sustainability.
There’s one more important point worth addressing. Some Black Locust suppliers claim that thermally modified wood lacks structural integrity and becomes brittle. And while that can be true with some manufacturers, it’s not the case with ThermaPro Wood Decking.
We use a next-generation, lower-heat thermal modification process that reduces structural strength loss from the typical 30% down to just 15%. To further enhance structural performance, our decking is manufactured in true 1.25” nominal thickness, which delivers excellent structural integrity.
Plus, this lower-heat process not only reduces brittleness—it also consumes less electricity, making ThermaPro Wood a smarter solution all around.
IN SUMMARY
Both Black Locust and ThermaPro Wood Southern Yellow Pine decking are excellent, all-natural, long-lasting options for decks and boardwalks. However, ThermaPro’s modified Southern Yellow Pine stands out in two key areas:
Dimensional Stability – Thanks to thermal modification, ThermaPro resists twisting, cupping, and cracking far better than Black Locust.
Price – With domestic production and efficient processing, ThermaPro Wood offers all the benefits at approximately one-third the price of Black Locust.
The choice is clear: ThermaPro Wood delivers superior performance and value.
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Want to learn more about thermally modified wood? Check out our education blog posts https://www.thermaprowood.com/blog/categories/education
Have questions you want answered about thermally modified wood? Then give us a call or email sales@thermaprowood.com.
