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About Accoya Wood

Accoya is the world's leading high technology wood. Created from sustainably sourced softwood, Accoya matches or exceeds the durability, stability and beauty of the very best tropical hardwoods.

Accoya is New Zealand grown Radiata Pine which has undergone a propriety acetylation process to produce a revolutionary timber product. This acetylation process alters the physical properties of the wood by transforming free hydroxyl groups (molecules that readily absorb and release moisture) in the timber into acetyl groups. The process is done at a purpose-built facility in The Netherlands.

The result is a durable, stable timber that equals or surpasses the leading timbers. Better still, the whole process does not add any toxic chemicals.


Accoya bridge passes over a busy motorway, it is expected to last 50 years

Installation Manual
Our full installation manual is available for download on our downloads page. This comprehensive 60-page manual explains the correct method for installing CertClad weatherboards to ensure compliance with the Building Code.

Close up detail of the Accoya bridge support structure

Timber Resource
All Accoya is New Zealand plantation grown pine from FSC certified responsibly managed forests. This independent internationally recognized accreditation gives our customers peace-of-mid as to where the timber came from and helps ensure the ongoing survival of our forests.

See our extra information page on Resource Certification for more about FSC.

Accoya is class one durable, furthermore it is guaranteed not to rot for 50 years in above-ground applications.

For the purpose of this guarantee, rot is defined as fungal decay that materially damages the timber caused by the soft-rot fungal species: Poriaplacenta, Coniophora puteana, Gloeophyllum trabeum, Corriolus versicolor, Serpula lacrymans and does not include common surface mould, mildew or any other organism either bacteria or fungi.

Scion (New Zealand Forest Research Institute) compared Accoya to commonly used hardwoods, H3.2 and H4 CCA treated Radiata Pine in both ground contact stakes and fungus cellar stakelets (an accelerated decay environment). In both tests Accoya dramatically out performed the durability of all the other timbers (including H4 treated Pine). The report "The Durability of Accoya Radiata Pine Sapwood Results from Ground Contact Tests after Five Years Exposure" is available from

NZ Radiata is treated in an acetylation chamber

Accoya woods exceptional durability is a result of the acetylation process. Acetylation is a chemical process which effectively changes the free hydroxyls (chemical groups that readily absorb and release water, causing shrinkage and swelling) within the wood into acetyl groups. This is done by reacting the wood with acetic anhydride, which comes from acetic acid (known as vinegar when in its 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, because it is no longer digestible, extremely durable.

We recommend a fungicidal coating be applied to prevent unsightly (but non-detrimental) surface mould.

Important Notes
Accoya wood has higher acidity levels than most timber and will cause oxidization or corrosion when in direct contact certain metals and moisture. Do not use Accoya in direct contact with copper, galvanized steel, powder-coated aluminium, zinc-alum, or zinc plated steel.

Stainless Steel (304 or 316) or brass fastenings and fixings must be used as these will not degrade like other metals.

The worlds most advanced wood is now available in New Zealand

Durability like no other wood, 50 years above ground, 25 years in-ground!


Accoya wood is improved right to the core, making it very durable

Certified FSC

All Accoya is New Zealand plantation grown pine from FSC certified responsibly managed forests and has class leading environmental credentials such as Cradle to Cradleâ„¢ Gold certification by the highly prestigious McDonough Braungart Design Chemistry (MBDC) organization.

Timspec The Timber Specialists
Official CertClad Supplier for New Zealand
64c Stoddard Rd, Mt Roskill
Ph: (09) 620-0260
Fax: (09) 620-0261
30 Kent St
Ph: (06) 379-9381
Fax: (06) 379-9382
9B Francella St, Bromley
Ph: (03) 384-5287
Fax: (03) 384-5289

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