Outstanding Performance

Extensive laboratory and field testing by leading institutes around the world (including in New Zealand, USA, UK, Sweden, Malaysia, Indonesia, the Netherlands and Japan) has shown the performance of acetylated wood to be extremely reliable.

Accoya® treated wood has been thoroughly tested for dimensional stability, durability, paint retention and in-ground conditions to ensure optimal performance. Indeed, it is so reliable that for many years it has been – and continues to be – used by scientists as the benchmark against which other treatments and modified timbers are measured.

Where to buy

Key Features

Dimensionally Stable
  • Swelling and shrinkage reduced by 75% or more
  • Doors and windows open effortlessly year round
  • Reduced maintenance costs
Outstanding Durability
  • Lasting 50 years above ground, 25 years in ground/freshwater Class 1 durability, surpassing even teak
  • Virtually rot proof
  • 70 year minimum service life stated by TRADA
Ideal for coating
  • Improved stability means coatings last up to two times longer
  • Easier to coat, less preparation and sanding required

Feature & Benefits

  • Ideal for all decking situations in extreme temperatures
  • Low thermal gain
  • Splinters are much less than other wood species when used for decking
naturally insulating
  • Offers improved insulation in comparison with commonly used hardwood and softwood species
  • Ideal for applications where energy conservation is important
  • Easy to machine and process
  • No special tools are required
  • Indigestible to a wide range of insects, including termites
  • Greatly reduced vulnerability
consistent quality throughout
  • Consistent, measurable modification quality from surface to core
  • No need to apply chemical preservatives when cut or planed
  • Process does not compromise the wood’s natural beauty
  • From FSC® and other regionally certified woods
  • Naturally renewable
  • The process does not compromise the wood’s strength
  • Hardness is increased
  • High strength to weight ratio makes it suitable for challenging applications
  • Protects the environment from the harmful effects of common treatments
  • May be safely reused, recycled and incinerated

Outstanding Durability

Cellulose is a major structural ingredient of wood but it is also a major food source for several different insects and decay fungi and makes a great shelter for others, too. Rot causes wood to degrade – particularly when it is used outdoors and exposed to moisture – limiting its service life. Thanks to the acetylation technology pioneered by Accsys Technologies, Accoya rot resistant wood offers you an environmentally compatible, stable wood that can be used with confidence in outdoor applications and will last for many, many years.

Simply the best

As ‘Class 1’ suggests, this is simply the best level of durability possible in wood. Whilst some wood species are naturally durable, natural durability is known to be a variable and inconsistent property.

Accoya wood, on the other hand, is consistently durable. The properties of every batch are analysed by standard scientific measurements after modification, enabling its durability to at least match and even exceed the performance of nature’s most durable species, including teak.

Additionally, durable woods tend to be slower growing species, whereas Accoya is made using fast growing, sustainably forested radiata pine, so old growth forests are not threatened or depleted to create Accoya.

Longer lasting

Accoya wood’s durability makes it very long lasting, at least:

  • 50 years above ground
  • 25 years in-ground or freshwater contact

Accoya wood forms an effective barrier to insect attack; it is indigestible to microorganisms and insects and therefore more durable to wood-destroying fungi and virtually rot-proof.

Where durability counts…

Heavy Traffic Road Bridge: “Several independent European research institutes tested Accoya’s suitability for this project. After rigorous testing, we found that its dimensional stability and incredible durability put it head and shoulders above other species and showed that it is suitable for laminating in large sections measuring 1080 x 1400 mm. Accoya is non-toxic and made from sustainably grown timber and these things were also considerations,” Sieds Hoitinga, Project Manager, Province of Friesland, the Netherlands.

Canal Lining: Certain environments are particularly punishing and few are harsher than canal banks where wood is used to hold back the earth, exposing it to water, microbe-rich soil and – most obviously at the waterline – air. Accoya water resistant wood offers unparalleled performance in this application, replacing tropical hardwood.

Decking: Applications like decking, where the wood is frequently wet and close to or in contact with the ground, demand a durable wood that is an effective durable and has an insect barrier. Acetylation has been shown to significantly improve performance against brown rot, white rot and soft rot. Accoya wood has also proven to be an effective barrier to wood destroying insect damage in multiple field tests and laboratory trails undertaken in many locations in the world. This includes tests with multiple species of termites.

Accoya Wood That Never Rots for demanding applications

Dimensional Stability

Dimensional stability can be defined as the degree to which a material maintains its original dimensions when subjected to environmental changes. With many materials temperature and humidity are critical factors. In the case of wood, swelling in damp or wet conditions and shrinkage in dry, hot conditions can have unwelcome implications: windows and doors may jam or let in drafts; wood may warp or split, leading to insect degradation and more frequent maintenance cycles; structures may become unstable. Accoya wood’s superior dimensional stability (resistance to swelling and shrinkage) matches or exceeds all the best species in the world, including Teak, Sapele, Iroko and Western Red Cedar.

Outstanding dimensional stability

Accoya wood offers outstanding dimensional stability in both radial and tangential directions (thickness and width) meaning that it has minimal swell and shrinkage and may be confidently used in applications where it will encounter varying moisture conditions – even in freshwater immersion.

Tests have shown a reduction in swelling caused by moisture uptake of 75% or more. From oven dry to water saturated conditions, the swelling and shrinkage of acetylated wood is only minimal and, in fact, better than tropical hardwoods.

Advantages of dimensional stability

  • Reduced swelling and risk of jamming in humid conditions
  • Better fitting windows and doors in all weathers
  • Less frequent coatings maintenance
  • Cladding that does not cup
  • Floors and decks that stay level
  • Decreased maintenance cycles

Accoya wood was the only wood that did not cup in this TRADA (Timber Research & Development Association) trial on wood cladding.

Extreme conditions

Accoya wood has been tested over prolonged periods in all types of weathering conditions – above ground, below ground and in freshwater – and has been proven to withstand even the toughest and most challenging of environments. Even after a prolonged period of immersion, Accoya window frames operate smoothly, without jamming.

Accoya wood has been used for replacement windows in two lighthouse restoration projects.

“The new windows have made a vast improvement to the property visually and in terms of energy and heat retention and have made a significant reduction in noise from the wind in such an exposed location.”

David Shaw, owner, Belle Tout Lighthouse


By significantly enhancing the durability and dimensional stability of fast-growing and abundantly available certified wood species, Accoya wood provides compelling environmental advantages over slow-growing hardwoods, woods treated with toxic chemicals and non-renewable carbon intensive materials such as plastics, metals and concrete:

The responsible procurement of wood plays a fundamental role in positioning Accoya as an environmentally compatible product. All Accoya wood is produced from well managed sustainable sources including FSC®, PEFC™ and other regionally certified woods.

Only abundantly available, fast growing source species such as Radiata pine are used to create Accoya. The use of wood species that produce larger volumes of wood over the same time span for the same area of land offers obvious environmental advantages.

The Accoya wood manufacturing process is non-toxic and adds nothing to the wood that does not already naturally occur in it.

The enhanced durability of Accoya wood facilitates a lifespan of at least 50 years above ground and 25 years in ground, improving carbon sequestration potential and lowering lifetime material consumption versus other materials.

Accoya wood’s outstanding dimensional stability and improved hardness results in lower maintenance frequency and therefore less coating use and waste over the product’s lifetime.

Compared to other durable wood species, Accoya wood offers superior thermal insulation, which provides energy conservation advantages when used in applications such as window frames and doors.

In the Cradle to Cradle® philosophy for which it holds the Gold certification, Accoya wood is understood to be non-toxic.

Accoya wood is fully reusable and recyclable. Reuse is recommended but Accoya may be safely incinerated for bio-energy.

Accoya wood is an environmentally compatible substitute for carbon intensive materials such as plastics, metals and concrete.

Green Life Smart Life™

Green Life Smart Life™ is a green building showcase home on the Rhode Island coast of the USA. The home is designed to demonstrate how families can make lifestyle choices that are sustainable and meet their needs without compromising the environment’s needs. Accoya was the ideal choice for the front and rear decks and contributed to the project’s LEED-H points in the category of Materials & Resources. The home achieved an official rating by the US Green Building Council as a GOLD certified LEED® for Home Project and was the first LEED-H Gold Home in Rhode Island.

Accoya wood – the responsible choice

In the water

In the Netherlands Accoya wood is proving to be a high performance, environmentally positive alternative to pressure treated wood and tropical hardwoods in civil works, including particularly demanding applications such as canal lining.

Early canal lining trials gave excellent results, with acetylated wood showing no discernible degradation at all, even after 10 years in the water.

On the water

The first boats to be made entirely of Accoya wood have been launched in the Netherlands.

Based on a design dating from 1958, the boats were previously built from tropical hardwood but the boat builder, Koo-Boten, is committed to building only sustainable and environmentally friendly boats and Accoya was therefore the obvious choice.

Open to the elements

In the 2010 Solar Decathlon, an international competition that challenges universities to design and build a self-sustaining, energy-efficient solar house, the University of Florida’s team, Project RE:FOCUS, sought sustainable, high performance materials for its innovative design. Accoya wood was chosen for adjustable exterior shading.

“Accoya wood really fell in line with our sustainable goals for the house.” Paige Mainor, Project RE:FOCUS design contributor.

Accoya long life wood is ideal for Decking


Accoya® wood’s superior coatings performance is primarily due to its outstanding dimensional. This effectively means that major coating systems can be used on Accoya® with significantly improved performance.

Dimensional stability & coatings

With Accoya wood, swelling and shrinkage is reduced by 70-80% and the resultant more stable surface allows coatings to adhere better. Dimensionally stable wood improves coatings life as paints and other film-forming coatings are not subjected to severe stretch and shrink cycles. In the end, the result is decreased maintenance frequency, resulting in:

  • Less time spent maintaining the wood
  • Less money spent on coatings
  • Less coating used overall during the service life of the wood
  • Less impact on the environment

Accoya works well with all known coatings systems. Extensive testing has been performed with opaque hybrid, opaque acrylic and  emulsions coating systems.

Perfect for coating

Return to Fife

This architect-owned private house near Glenrothes, Fife, used approximately 30m2 Accoya wood profiled facade cladding and was completed in July 2006. The cladding was factory coated with translucent Sikkens Natural Balance coating system giving a smooth contemporary finish. After 6 years, the cladding shows no sign of decay, despite the property’s far northern latitude and 10km proximity to the sea. The coating continues to perform well, with no blistering or cracks. The slightly dirty appearance of the cladding is due to tree sap from surrounding trees but the owner reports that this is simply and easily washed off.

Tweedbank revisited

Twenty one energy efficient homes featuring windows and doors clad in Accoya wood were completed for Eildon Housing Association at Tweedbank in the Scottish Borders area in 2007. Eildon chose Accoya wood after analysis of the product’s aesthetic and durable qualities. More than 11,000 linear metres was used, finished with a Sikkens coating by Environmental Coatings. After more than 3 years in situ, there are no signs of rot, decay cracking or blistering as is common in this challenging environment and colour retention is excellent.

“We are delighted with the performance of Accoya, which reflects our commitment to increased sustainability levels and innovative technology.” Laurence Cox, Eildon.

In the shade

Accoya wood was used as part of a bespoke solar shading system by Levolux in this Scottish Widows office in Edinburgh, Scotland. 1,060 wood fins were used in combination with glass fins and Matrix XL Brise Soleil.

Levolux was able to offer a 10 year warranty for the finish and a 60 year life expectancy and over 2 years later the fins look and perform as new, despite the challenges encountered in this type of thin profile, fully exposed application.

Quality & ease of use

Wood is a natural material and each piece is unique. This is partly what makes it so aesthetically pleasing and yet it can be a source of frustration and uncertainty when looking for guaranteed performance quality. However, with Accoya wood you can be sure of its consistent quality, durability and dimensional stability.Wood acetylation is a process that has been studied by scientists around the world for more than eighty years. The Accoya wood production process combines this work with years of proprietary research and investment to deliver consistent results on a commercial scale. Unusually, the effectiveness of the process used to manufacture Accoya wood is measured after the wood has been produced, using an array of sophisticated and proven analytical techniques.

Outstanding durability

Each batch is analysed and Accoya wood always meets the requirements of Durability Class 1 for Use Classes 1-4 in accordance with EN 350-1 & EN 335-1.

Consistent quality throughout

Because Accoya wood is modified all the way through, rather than just at the surface, when it is cut, planed or jointed there are no exposed unprotected surfaces in any dimension. This completely removes the need to apply additional chemical preservatives as is necessary with unmodified or envelope treated woods.

Excellent machinability & ease of fixing

Accoya wood is easy to machine and process manually, creating no challenges for product manufacturers and end users. Accoya wood can be fixed in the same way as other commonly used softwood species. As with most durable woods, Accoya contains a small amount of acid. It is therefore strongly recommended that corrosion resistant fixings, such as high quality stainless steel, are used.

Retained strength & hardness

The manufacturing process does not compromise the wood’s strength. In fact, the hardness of the wood is increased and because Accoya wood has a high strength to weight ratio, it is suitable for challenging applications – even heavy traffic road bridges.

Naturally beautiful wood

Last but not least, Accoya wood is naturally beautiful. It is comparable in colour to the original source species, so that you can achieve a natural look in your projects if you wish or it may be easily coated in a wide range of colour finishes. The choice is yours.


Wherever you can imagine wood, imagine Accoya wood…

…building bridges

Accoya wood inspired OAK architects to design two wooden heavy traffic road bridges for the city of Sneek in the Netherlands. Accoya was finger jointed and laminated into large sections measuring 1.08 x 1.4 metres to create these innovative structures, the first of their kind in the world.

…opening doors & windows

Accoya wood is a brilliant material for windows and doors as it offers improved thermal insulation in comparison with commonly used wood species and is more durable and dimensionally stable than the best tropical hardwoods. Coatings last longer and it is perfect for translucent or opaque coatings … whatever captures your imagination.

…finely clad

Accoya wood is suitable for cladding, siding and façades where aesthetics, stability, durability and less frequent maintenance are considerations. Here it is used to clad a contemporary extension using an inclined open boarding system, finished with an environmentally friendly dark stain. This is only possible using a wood as stable and durable as Accoya.

…on deck

In specifying decking, jetties and pontoons, beauty, strength and all-weather performance are important. A dimensionally stable material that will stay flat and has very minimal bow, cup, warp and split and will not be affected by fungi or rot is desirable. It is also important that the wood is non-toxic and therefore safe for people and animals. Accoya wood meets these requirements.

…in the shade

Accoya wood is an excellent choice for shutters, louvres and solar shading. At Scottish Widows’ Exchange Place development, eye-catching bespoke solar shading and ventilation louvres were incorporated to prevent excessive heat gain. The system included 1,060 Accoya wood fins. The solar shading has a life expectancy of 60 years and the finish applied carries a 10 year warranty.