Your unequalled hardwood decking choice

There’s no doubt that Thermory Benchmark with thermally modified ash will produce a great-looking deck. But several equally important properties are concealed beneath its attractive surface – durability and easy installation. These qualities can be found, to a high standard, in all of our thermally modified ash decking.

Thermory’s thermo-ash decking boasts the highest available durability class and it doesn’t contract or expand. It’s also knot-free and possesses a deep, rich tone. The selection includes profiles that allow you to install the deck using the world’s simplest method and without visible screws. And unlike tropical wood, ash won’t spoil your tools or give off toxic dust. Thermally modified wood is natural, chemical free and environmentally safe.

Thermory Benchmark thermo-ash cladding C20 and decking D45J, Private house- n Saaremaa, Estonia
Application: Decking
Species: Thermally modified ash
Modification level: Intense
Use: Exterior
Durability class: 1 (25+ years’ protection against wood decay)
Finish: Unoiled
Texture: Smooth
Installation types: Visible, hidden
Installation methods: Screws, clips, PaCS

Comfortable, knot-free decking that’s naturally durable

knot_free wood


An even, aesthetically pleasing look and feel



A splinter-free, comfortable deck



Thermally modified wood is more durable with a lower moisture content

Thermory cladding durability


Thermory’s thermo-ash cladding has the highest available durability class



The decking doesn’t overheat in the sun



Wood sourced from sustainable forests with chemical-free modification

Why choose Benchmark thermo-ash decking?

If you’re looking for a durable and stable material that’s suitable for outdoor use, Thermory Benchmark thermo-ash decking is right for you. It’s the ideal choice for those who truly care about the environment and wish to reduce their ecological footprint.

Thermally modified ash is an environmentally friendly alternative to tropical wood – our wood comes from sustainably managed forests and we never purchase timber that originates from endangered woodland, tropical forests or rainforests.

Thermally modified ash has similar durability characteristics to tropical wood (class 1, 25+ years) with superior dimensional stability.

Thermally modified wood’s lower moisture absorption capability and rate results in less moisture-induced wood deformation, which means that the wood shrinks and expands less when used outdoors.

Our thermally modified ash is a nature-friendly material as no chemicals are used and no hazardous waste is generated in the thermal modification process.

Read more about thermal modification

Additional options for easy installation and a flawless finish



An attractive finish with no visible screws



Reduces waste, saves expenses

Thermory easy installation


Ingeniously simple fixing methods

Thermory brushed wood


Highlights the wood’s natural grain


Thermally modified ash is a responsible alternative to tropical timber

Tropical timber is considered the gold standard for durability in wood. This wood is of course valuable, but of rainforests are cut down to acquire it. We offer the alternative of using tree species that, after thermal modification, offer wood with comparable durability and functionality to that of tropical tree species – without destroying rainforests.

Our thermo-ash decking is naturally as durable as tropical wood, or even more so, with a rich deep color. Unlike tropical hardwood, thermo-ash is environmentally friendly, non-toxic and rot resistant for at least 25 years if installed properly.

Ash is lightweight and durable

Ash (Fraxinus excelsior or Fraxinus americana) is a deciduous tree of the Oleaceae family that grows in Europe and North America. Ash wood is valuable, durable and strong, and with its decorative look and attractive texture, it’s the perfect material for walls and floor surfaces. Thermal modification gives ash exceptional durability and an exotic tone, making it an environmentally friendly alternative to tropical deciduous trees.

The color of the wood changes over time

Thermal modification gives ash wood an exotic deep brown color.

As with any wood, the surface of thermally modified ash will fade to a natural silver-gray color over time. This process starts immediately after the products are installed and can take a few months to several years depending on how much UV light they’re exposed to. The durability of the boards is not affected.

If you would like to preserve the darker tone of thermally modified wood, we recommend oiling the boards once a year using a UV-resistant oil.

Deck maintenance. To oil or not to oil?

Thermally modified decking boards do not necessarily require surface treatment, but regular maintenance and oiling will refresh the appearance of your deck and make it easier to clean.

We recommend cleaning and maintaining the deck before the start of the summer season.

Lightly sanding faded boards will remove the silvery surface colour and restore the wood’s original appearance.

If you would like to preserve or change the tone of thermally modified wood, apply UV-resistant oil to the boards once a year.

If you would like to preserve the tone of boards that have turned grey over time, use colourless oil without a UV filter on the boards.

The oil should be applied only to clean, level, dust-free surfaces.

Download decking maintenance guide

Recommendations for installing Benchmark thermo-ash decking

Using the correct installation techniques will result in the most beautiful and long-lasting Thermory decking.

We recommend using Thermory Ash or Thermory Spruce (both durability class 1) for the . This will ensure that your substructure lasts at least as long as your decking.

Choose the PaCS Strip or the T-4, T-6, or TENI clip fixing to achieve a deck surface without any visible screw holes or screws.

If you decide to use screws when fixing your decking, we recommend pre-drilling the screw holes in the boards to avoid splitting the wood with the screws. The diameter of the drill bit must be 1 mm larger than the screw diameter.

By choosing decking boards with end-matching, you can minimize time, labor and material costs when installing boards of different lengths. The load-bearing capacity of the end-matched part of the decking is verified, and the two boards don’t necessarily need to meet directly over a joist.

Apply end wax to the ends of every decking board prior to installation to ensure a longer service life.

Follow the decking installation guide for correct installation.

Download decking installation guide

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