Thermo Ash

Thermory American Ash



This attractive and versatile material is produced by Thermory, the leading producer of thermally modified Ash.

Established in 1997 and based in Estonia, Thermory have over 15 years experience in perfecting the thermal modification of American Ash.

The end result is a beautiful material, rich in colour and distinctive grain, with all the advantages of thermal modification.

Using modern Scandinavian kilning technology, American Ash is pre-dried, heated (215°C for “INTENSE” thermal modification) and re-moisturised to prevent brittleness.

The process uses only heat and water and is completely chemical free with the energy for the kilns being generated from wood waste. The American Ash is fully FSC certified, achieving the highest environmental standards.

Advantages of thermal modification

Thermal modification brings many advantages.

One of the main advantages with the thermal modification of American Ash is to convert a “non-durable” species into a product that achieves durability Class 1, the same classification as some tropical species such as Teak or Ipe (see test reports below)

Increased stability results from the process making Thermory Ash resistant to temperature and humidity variations. It has reduced permeability and increased insulation properties, limiting the expansion and contraction and improving the performance of the timber in service.

Unlike an “envelope” chemical treatment Thermory Ash is treated right through to the core, allowing the material to be cut, drilled and planed like ordinary wood, but without affecting the durability or stability. In fact the working properties are greatly improved due to the removal of the resins.

The appearance is changed dramatically, turning the Ash a rich walnut brown colour with a highly attractive grain figure.


Thermory Ash makes a very attractive deck for both residential and commercial use.

Available in 20mm and 26mm thicknesses and 132mm and 160mm widths. (150mm width is available to special order)

The “TENI” clip system avoids the need for unsightly face fixings and also provides improved air circulation around the deck boards. Also the “TENI” clip system allows for the removal and replacement of a single board, should this ever be necessary, without the need to disturb the rest of the deck. The deck boards are structurally jointed on their ends and push together allowing a continuous laying of the board without the need to joint the boards over a joist. This reduces the length wastage to practically zero.

Oiling of Thermory Ash is optional, and recommended if the original colour is to be prolonged.

Thermory Ash is suitable to use without oiling and its durability will be unaffected. However, as with all timbers it will naturally turn to a silver grey colour with exposure to UV.


20 x 132 “Karakum Intense Ash”
Shrink wrapped Installation pack containing
1pcs 2.7m, (1pc 1.5m + 1pc 1.2m) (1pc 1.8m+1pc0.9m), 1pc 2.7m
End matched for continuous laying
10.8 linear metres = 1.49m3 laid coverage
Pack weight 16.8Kg

20 x 150 “Karakum Intense Ash”
Available to special order

26 x 160 “Karakum Intense Ash”
Shrink wrapped Installation pack containing
1pcs 2.7m, (1pc 1.5m + 1pc 1.2m) (1pc 1.8m+1pc0.9m), 1pc 2.7m
End matched for continuous laying
10.8 linear metres = 1.82m3 laid coverage
Pack weight 26.5Kg

TENI clip
20mm clip and screw – box of 100
26mm clip and screw – box of 100

26 x 145 Calibrated blank
Suitable for machining bespoke profiles.
Lengths – 0.8m to 3.6m according to requirements

Installation of Thermory Ash decking

Please refer to the Installation guide below for full guidance on the correct installation of your deck.

Quick Tips

Set joists at 400mm centres
Avoid ground contact of the deck boards and allow air circulation within the design.
If face fixing always pre-drill and countersink
Use stainless steel screws
Seal cut ends
Oil upon installation if you would like to prolong the colour. Maintain annually.


Species: American Ash - Fraxinus Americana
Thermal Modification: Intense – Maximum temperature 215° C
Durability: CEN/TS 15083-1/2005 Annex D: Class 1 – Very Durable
Density: Average 590 kg/m3
Hardness: Average 29.4 HB (N/mm2)
Bending Strength: Average 96.6 N/mm2
Equilibrium Moisture: 7.9%
Environmental: FSC® Chain of custody