Welcome to the world of Accoya®

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Ideal for windows, doors, cladding, decking and many more applications

Accoya® wood is a high performance wood. Created from sustainably-sourced wood, Accoya® undergoes a proprietary, non-toxic acetylation process that permanently modifies the wood to the core.

The result: an environmentally friendly solid wood with durability, dimensional stability and beauty that matches or exceeds even the best tropic hardwood.

Accoya® wood is sourced from sustainable sources, including FSC® and has class leading environmental credentials such as Cradle to Cradle™ Gold certification by the highly prestigious McDonough Braungart Design Chemistry (MBDC) organization.

Accoya® wood is perfect for demanding applications such as windows and doors, where it is important that tolerances are tight yet regardless of the conditions, they open year round. Accoya® is perfect for siding where wood’s natural beauty is desired, but sustainability and high performance are of the utmost importance. In decking, where it is important that boards do not warp, twist, bow split, Accoya® is up to the challenge.

Click through our projects to the right or find more pictures on our Timspec Homepage.

Red Beach House

Auckland; Trevor Wilson @ Architecture 37


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® 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 modifications are measured.

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
Perfect For Coating
  • Improved stability means coatings last up to two times longer
  • Easier to coat, less preparation and sanding required

Features & Benefits

Naturally Insulating
  • Offers improved insulation in comparison with commonly used hardwood and softwood species
  • Ideal for applications where energy conservation is important
Excellent Machinability
  • Easy to machine and process
  • No special tools are required
Insect Barrier
  • 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
Naturally Beautiful Wood
  • Process does not compromise the wood’s natural beauty
From Sustainable Sources
  • From FSC, PEFC and other regionally certified woods
  • Naturally renewable
Retained Strength & Hardness
  • The process does not compromise the wood’s strength
  • Hardness is increased
  • High strength to weight ratio makes it suitable for challenging applications
Non-Toxic & Recyclable
  • Protects the environment from the harmful effects of common treatments
  • May be safely reused, recycled and incinerated

Outstanding durability

Accoya is already inspiring architects, designers, specifiers and individuals around the world with its outstanding qualities and the possibilities it offers for using wood in exterior applications.

Class 1 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 wood offers you an environmentally compatible, durable 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.

Outstanding Durability
Insect Barrier

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 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 mould and 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.

Dimensional Stability

Here we’d like to let you know more about Accoya® wood’s outstanding dimensional stability and why this is an important factor when using wood in external 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

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.


We’d like to show you that Accoya® wood truly is a leading edge material that treads softly on the earth.

If you like to use wood in outdoor applications and are considering ways in which your projects can be more sustainable, achieve a lower carbon footprint and increased energy efficiency, Accoya wood may well be the answer you’ve been waiting for.

Higher Leeds and Breeam Scores with Accoya

In the green building industry LEED and BREEAM are clearly the most rigour and internationally recognized certification systems. Both are based on various building related environmental indicators including sustainable energy, -water and -material use.

Better Breeam Scores

BREEAM is the most important sustainable building system in North-western Europe. Because of the low environmental impact based on Life-cycle assessment (LCA), the low maintenance, the innovative character and the sustainable sourcing (always FSC or PEFC), application of Accoya yields a higher BREEAM International score (MAN 5, MAT 1, MAT 3, Inn 1).

More Credits for Accoya in Latest Leed Version

Whereas Accoya was already rewarded in the previous (v2009) LEED BD+C system through the sustainable wood sourcing (credit MR 7), in the latest version v4, because of the transparent environmental reporting (LCA, EPD, carbon footprint), the benign environmental profile including C2C Gold certification, and even the light colour ( heat island reduction), application of Accoya contributes to even more credits.

Sustainable Accoya® Home Receives Platinum Leed Certification

One of the USA’s most sustainable family homes, constructed with the extensive use of Accoya wood, has been awarded platinum level LEED certification – the highest recognition available from the US Green Building Council.


If the need to frequently maintain coatings on wood is a downside for you, not just in terms of time and cost but also in terms of the associated environmental impact, then you will welcome the coatings performance advantages associated with Accoya® wood.

Superior Coating Performance

Accoya® wood’s superior coatings performance is primarily due to its outstanding dimensional stability. 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 transparent alkyd emulsions coating systems.

Quality & Ease of Use

Recently we’ve shown you some reasons why Accoya® wood is such an exciting and groundbreaking product – one that will enable you to use wood with absolute confidence, even in outdoor applications.

In this final part of our introduction series we’d like to let you know just what it is that makes Accoya wood consistently excellent and talk about some of the practicalities of using it.

Consistent 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.


Building Bridges

Accoya has been used to create a unique “floating” bridge in the Dutch city of Bergen op Zoom.

Ro Koster and Ad Kil, of Bergen op Zoom-based RO&AD Architects, who also mastered the famous and award winning Moses Bridge in Halsteren, designed the 80m floating pedestrian bridge to allow access to the 18th century fort’s entrance. Its snake-like path mimics the journey and motion of the boats which originally travelled there.

Windows & Doors

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. Following third party testing of Accoya, its expected service life is now independently reported as extending to 70 years when used for window joinery in the UK and Europe as well as being Carbon Negative over its life cycle. Coatings last longer and it is perfect for transparent, 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.

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.

Acetylation Process

Accoya is based upon acetylated wood technology, a process that has been studied by scientists around the world for more than 80 years.

This method of improving wood has been proven to deliver such superior performance that it has long been used as the "gold standard" against which other methods are measured.

Acetylation Process

The physical properties of any material are determined by its chemical structure. Wood contains an abundance of chemical groups called "free hydroxyls". Free hydroxyl groups absorb and release water according to changes in the climatic conditions to which the wood is exposed.

This is the main reason why wood swells and shrinks. It is also believed that the digestion of wood by enzymes initiates at the free hydroxyl sites - which is one of the principal reasons why wood is prone to decay.

Acetylation Process

Acetylation effectively changes the free hydroxyls within the wood into acetyl groups. This is done by reacting the wood with acetic anhydride, which comes from acetic acid (vinegar when in dilute form).

When the free hydroxyl group is transformed to an acetyl group, the ability of the wood to absorb water is greatly reduced, rendering the wood more dimensionally stable and extremely durable.

Acetylation Process

Acetyl groups are already naturally present in all wood species. This means that the manufacturing process adds nothing into the wood that does not already occur within it.

The end product, Accoya® wood, does not add toxins to the environment. The effect of altering the wood's chemical structure, as opposed to merely altering its chemical content, is to create an end product that is dramatically superior to its source species.

Acetylation Process

Accoya wood is modified right through the cross section whereas, by contrast, virtually all other treatments merely insert chemicals (such as oils, ammonia or metal compounds) into the wood, improving durability, to a degree, but not dimensional stability.

Accoya Academy

Accoya wood is the world’s most durable, stable and sustainable timber ideal for windows, doors, cladding & decking and has a Minimum Service Life of 60 Year. See for yourself, why not learn more about Accoya, modified wood by Accsys Technologies.

Accoya Academy
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Accoya® Wood used for decking for private residence in Southern Italy

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64c Stoddard Road
Mt Roskill, Auckland

Head Office Tel: (09) 620-0260 or

Technical Specialist (North Island):
Jonathan Rugg 021-283-6973  jonathan@timspec.co.nz
Technical Specialist (South Island):
Stephen Norris 021-283-6972 stephen@timspec.co.nz
General Enquiries (North Island):
Helen Barth 021-283-6967 helen@timspec.co.nz