Burnt Ash | Thermally Modified American Ash

What is Burnt Ash?

Burnt ash is thermally modified American White Ash. American Ash is grown in mostly grown in North America, it is an attractive and versatile timber but only suitable for interior applications because of its low durability class. The thermal modification process increases the durability of American Ash which means its suitable for external use. Once thermally modified we call it Burnt Ash.

Quick Link, Durability Class: https://www.mortlock.com.au/news/how-long-does-timber-cladding-last

What is Thermally Modified Timber?

Thermal Modification is a chemical free process that enhances an inapt wood species performance with heat and steam, so it increases the durability of the timber. The high heat modifies the cell structure of the wood and makes it highly resistant to rot while greatly reducing expansion and contraction.

The process requires a purpose-built oven to ensure every piece of timber is modified to the correct specification and quality. At the end of the process the moisture content of the timber is around 7% and the properties of the timber have been permanently changed.


Because of its high durability and excellent stability properties, Burnt Ash is a great option timber for external timber cladding, timber ceilings, screening, and decking. It also chars well and is one of there best options available in our Shou Sugi Ban Charred Timber Range.

Burnt Ash is available in the following products:


The thermal modification process darkens the white ash into rich medium to dark chocolate colour.

Colour Variation

Burnt Ash varies from deep red to dark brown

Available Finishes


As timber is a natural product images above may not fully reflect the true colour and natural variation of the timber, we recommend you view samples and discuss the options before making your final decision.​

Enviro Clear is a water based product for interior use only. It is a film forming, non-yellowing coating which is easy to clean and requires minimal maintenance.

Sioox Weather Protection Coating is wood modification coating which speeds up the timber weathering process while providing a protective layer over the surface. After application, the coating is activated by moisture and a curing reaction commences which forms a flexible silica surface. Weather Protection Coating is a proven water based silicate treatment which, if correctly applied and cared for, provides long life up to 15 years and a beautiful natural finish. This product provides a more even weathered finish than naturally weathered timber. Image of sample shown above with the weather protection coating has been in the weather for 2 months.

Shou Sugi Ban, further information at https://www.mortlock.com.au/what-you-need-to-know-shou-sugi-ban/

Burnt Ash Properties

OriginNorth America
SustainabilityFSC available on request
Janka Hardness6
Density (Dry)700kg/m3
ShrinkageDimensional approx. 0.5%
Lyctid SusceptibilityResistant
Lyctid SusceptibilityResistant
FireSatisfies BCA C1.10a Group 3 (Not BAL Rated)