Durable wood without adding anything to it
Thermal modification bakes wood at high temperature in a steam atmosphere, about 215 °C for Thermory's ash. The heat changes the wood's sugars so they no longer feed decay fungi and the board absorbs far less water. Thermory states that nothing is added in the process: no preservatives, resins or plastics, only heat and steam. The result is rated Class 1 for durability, with 25 or more years of rot resistance per Thermory.
Ash, made outdoor ready
Ash on its own is not durable outdoors. Thermally modified, it becomes a deck board with a deep, even brown color through the board, a smooth surface Thermory describes as low splintering, and much better stability than untreated wood. It gives clients who want a hardwood deck an alternative to tropical species.
Weathering and care
Like other unfinished wood, thermo-ash weathers to silver gray in sun and rain. An exterior oil slows that and keeps the brown. Modified wood is also more brittle than untreated wood, so it is pre-drilled at board ends and fastened with the systems Thermory specifies.
How it compares
Kebony and Accoya modify pine with a liquid; Thermory modifies ash with heat alone. All three avoid plastic, which is why they share our eco decking page. Warranty terms vary by product and market, so we attach Thermory's current warranty document to your quote. Installation is covered on our deck installation page.
Common questions
What is thermally modified wood?
Wood heated to high temperature in a steam atmosphere. The heat changes its chemistry so it absorbs less water and resists decay, without adding preservatives. Thermory uses heat and steam only.
Is thermo-ash decking splinter free?
Thermory describes its Benchmark ash as smooth with minimal splintering. No wood deck is guaranteed splinter free, but modified ash is far smoother than pressure-treated pine.
Where these facts come from
- Thermory Benchmark thermo-ash decking page and ash decking data sheet: species, process, temperature, durability, moisture content, profiles
- Thermory hidden fastening systems: fastening
Specifications can change. We confirm them against the current manufacturer data sheet on every order.
