As the first company to produce acetylated wood on a commercial scale, Accoya® is leading the charge in providing durable and dimensionally stable wood for a variety of applications. In the acetylation process, softwood is essentially turned into a hardwood through the introduction of a non-toxic vinegar-like solution, creating a new type of wood that is durable all the way through the board, not just on the surface. In practice, this allows for a wood product that is significantly protected against the elements, making it perfect for installation in exterior environments where a standard sealed wood product would fail after only a short amount of time.

At Hewn, we build upon the extraordinary properties of Accoya® wood by applying our proprietary color and finish techniques to create beautiful, unique, and long-lasting wood products, suitable for a variety of applications, and customizable for the specific needs of your project.


Endless Versatility

The uniquely durable properties of Accoya®, created using an all-natural process, allow the wood to be utilized for a variety of purposes. Our sales representatives can customize your order to fit your precise needs and use-case scenarios.

Exterior Siding

Sealed for optimal protection against the elements

Interior Paneling

Durable enough for high-traffic commercial areas


Insect and rot resistance in a real-wood product


Widths: 1×6, 1×8
Thickness: 3/4″, 7/8″, 1½”


Greater than 9 rating per AWPA E7

Moisture Content

3-5 % at 65% relative humidity, 20°C

Density and Spread

65% RH, 20°C, Average 32 pcf, Range 27 to 37 pcf

Fire Rating

Class C (ASTM E84) and D (EN14915)

Thermal Conductivity

ASTM C177, = 0.102 – 0.120 W/m∙K

Janka Hardness

ASTM E143, Tangential = 972 psi, End Grain = 1,484 psi


Approved by WDMA as compliant with WDMA I.S. 4. Certified as compliant with Cradle-To-Cradle with Platinum Level Material Health Certificate.

Acetylated wood, at-scale.

Acetylation has been studied and practiced in the wood industry for more than 70 years. The process, by which wood is effectively “pickled” in an all-natural vinegar-like substance, was once considered impossible to produce in large quantities. With Accoya®, however, these barriers have been eliminated, and this durable real-wood non-toxic product can be produced and purchased at-scale. 

And with Hewn’s expertise in coloring and finishing, Accoya® can be elevated to the next level, creating a timeless look and feel perfect for your next commercial or residential project.


Standard Milling Profiles

5/4×6 Clear Square S4S
Actual Dimensions: 3/4″ x 5 1/2″
Lengths: 8′, 10′, 12′, 14′, 16′

1×6 Clear 90 Degree Shiplap
Face: 5″
Gap: Tight, 1/4″, 3/8″, 1/2″
Actual Dimensions: 3/4″ x 5 1/2″
Lengths: 8′, 10′, 12′, 14′, 16′

1×6 Clear T&G w/Nickel Gap
Face: 5 1/4″
Gap: Tight, 1/16″, 1/8″, 3/16″, 1/4″
Actual Dimensions: 3/4″ x 5 1/2″
Lengths: 8′, 10′, 12′, 14′, 16′

* Some milling profiles may be unavailable on certain finishes, including (but not limited to) our Heavy Char options. Please contact our sales representatives for additional information and alternative options.

The best way to honor the past is to preserve it. Our expert team of craftsman are continually seeking and sourcing only the finest materials available. Accoya® the high performing solid wood combined with Hewn’s specialty finishes makes for the longest lasting and most versatile wood on the market today. Accoya is the most moisture and weather resistant wood we have found.
With less maintenance than conventional alternatives, it is the very best option for exterior siding. Its longevity and durability make it an ideal choice for challenging interior and exterior commercial and residential applications. Accoya’s structural integrity and stability makes it a great substrate for a variety of applications a great platform for a variety of applications and is the only wood we use for our heavy char Shou Sugi Ban. Sustainably sourced, Accoya’s natural process far out-performs pressure treated alternatives, making it a better choice for the environment.