Accoya Wood: Durable, Stable, Modified Without Toxins

April 26th, 2011 by Cathy Rust Leave a reply »


Bridge made from Accoya

I was at a presentation, hosted by Upper Canada Forest Products, to hear about the features of Accoya wood. This is a wood product which looks really interesting specifically for any outdoor use. Matt Roberts is the Technical Sales Manager for the Americas for Accoya, and he presented on this product.

The product  was introduced in 2007 in The Netherlands. Accoya is a pressure-treated wood, however, it is treated with non-toxic ingredients, and it will last 50 years or more when exposed to outdoor weather elements. The entire wood piece is treated with an acetylation process so that every fiber of the wood is exposed to the acetylation process, not just the outside layer. What that means is that cut ends exposed to harsh weather will stand up just as well as the rest of the wood. The treatment process used actually changes the molecular structure of the wood and makes it more durable. Unlike traditional pressure-treated wood, however, it is completely non-toxic. The chemical used is acetic anhydride, a derivative of acetic acid, which is the base of vinegar. In fact, Matt told us that the wood gives off a faint vinegar smell when it’s being worked with.

Durability: It has an above ground outdoor guarantee of 50 years and a below ground and fresh water guarantee of 25 years. This is a pretty amazing guarantee for a wood product that will be exposed to all the weather elements.


swellometer measures absorption of water

Stability: Because the acetylation process keeps wood from bonding with water, it is hardly affected by the changes in temperature or humidity. In fact, at the beginning of the presentation, Matt put a piece of Accoya and an untreated piece of wood in a small tank of water and measured their ability to absorb moisture over the length of the presentation (about an hour). At the end there was a significant amount of swelling observed in the untreated wood, and barely any in the Accoya wood. Note the measurement was performed by a — I kid you not — “swellometer.”

Insect resistance:, Termites and other insects will stay away from it if there are alternative food choices (ie., other available wood sources), for it to eat.

Finish: The wood comes “rough hewn” and needs to be finished and sanded. Stain and paint last longer on Accoya than on regular untreated wood because of its stability. There is no contracting or expanding, which means paint and stain don’t wear as quickly.

Type of wood used: The wood used is a soft wood called Radiata Pine. It acetylates well which is why Accoya has started out with this wood. Although once it has been treated with this procedure the wood becomes 50% harder than in its original condition.

Decking made from Accoya

FSC certified: The wood used for this treatment is sourced out of well-managed, FSC-certified forests in Chile and New Zealand and treated at the main facility in The Netherlands. Eventually, the company will be licensing out the technology to wood treatment facilities worldwide to make logging, milling and manufacturing close to local markets.

Applications: Accoya is an excellent wood choice for a variety of residential applications: In addition to windows and doors, Accoya can be used for exterior siding, decking, shutters, fences, sound barriers, outdoor furniture…. (Two window and door manufacturers already use Accoya, Bonneville and Dynamic.)

One thing to note: because of the acidic nature of the wood, it was suggested that a few hardware materials such as zinc or galvanized steel be avoided because of their likelihood of being oxidized. Better choices are stainless steel, anodized aluminum, brass, any epoxy or ceramic coated hardware.

Wood frame made from Accoya. Note mitred corners will always remain stable

Cost: The cost of Accoya is the equivalent of a tropical hardwood, however, longevity of the product should be taken into account when considering pricing. This wood is ideal for specialty products with long-term exposure to the elements: windows, doors, shutters, wood trim, etc.

Accoya is available through Upper Canada Forest Products and is sent to manufacturers for further applications.

(Note: photos courtesy of  Accsys Technologies, PLC)



  1. Cathy Rust says:

    Hi There,
    I had a look at the Accoya website and this is their explanation regarding paintability:
    Does Accoya® have different paintability?
    Yes. Due to the improved dimensional stability of Accoya® wood (significantly reduced swelling and shrinking), maintenance of the coating system can be increased to 3 to 5 times normal life. Extensive tests have shown better coatings adhesion and reduced costs in applying coatings in a manufacturing environment. The company is working closely with coatings manufacturers, including Teknos, Sherwin Williams and Guard Industrie, to test their systems used in conjunction with Accoya®.
    It’s best to confirm with your Accoya supplier.

  2. Peregrine Wood says:

    Can you use linseed oil exterior paint (eg., Allback) on accoya wood?

  3. Mark Mah says:

    The wood is perfectly safe for any indoor application because the wood and process are non – toxic.
    Because of the process, there is a slight vinegar smell. You would need to seal the area well to ensure the slight odor doesn’t affect how you use the space. I would suggest taking a small sample piece and finishing it to see how you feel about the residual smell – if it is there at all.


  4. This stuff sounds amazing. Being from the south, I love the part about termite resistance. Are there any indoor applications for it?


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