Outside of building showing windowsAccoya wood has been used for the window and door fittings in a development located near to Abbey Road in the St John’s Wood area of London. Accoya was chosen for its proven stability, thermal properties and what we believe to be its unique 50-year guarantee.

Project and location: 10 high-end town houses in the St John’s Wood area of London
Architect: Robert Adam
Structural design: Byrne Looby
Construction company: Carey Group
Delivery partners: Sidra Capital and Dwyer Property
Window manufacturer: SB Joinery (https://www.sbjdanebury.com)

Close up of wood window showing profile and window latchThe windows and doors were a flush casement design created after hours of design detail meetings to meet the clients needs. The windows were a project specific design with slim double glazing and a specific client requested internal moulding detail. SB Joinery who made the windows said that,

Using Accoya on this development was a dream. No timber movement, no re-visits to site means no on-going hassle for the clients. Accoya is a hassle free product. If we had our way we would make all external joinery where possible from it!

Accoya wood is produced through a modification system that enhances the durability and dimensional stability of timber. This enables it to be used in situations where previously we may have relied upon durable tropical hardwoods or plastics such as uPVC.

75 years after the start of research into the modification of timber, usually Radiata pine, by acetylation the process is now a commercial reality. Increasing scarcity and concerns over the traceability of durable tropical hardwoods from sustainable forests along with tighter legislation around the use of toxins in existing preservative treatments have helped drive the commercialisation of processes to improve the performance of timber.

Accoya wood is a modified wood system based on acetylation, a process which alters the cell structure by transforming free hydroxyl groups (containing oxygen and hydrogen) within the wood cell walls into acetyl groups (containing oxygen, hydrogen and carbon). This is achieved through a patented system involving vacuum treatment of kiln dried timber with acetic acid – essentially just vinegar. Transforming these free hydroxyl groups is key to improved durability and stability as it is to these sites within the cell wall that water can be absorbed and released as climatic conditions change thus leading to expansion and contraction of the timber. Acetylation improves stability by 80%.

Increased stability of Accoya wood not only means that warping, bending and twisting are reduced or eliminated it also has benefits for surface treatments as cracks and fissures are smaller so paint finishes are not disrupted thus increasing their life span and reducing maintenance cycles. The modification process also ensures that timber is treated right the way to the centre – so there is no need to treat cut ends on site.

Accoya wood is increasingly being chosen by clients who recognise the positive contribution this material can play in their projects. Improved stability also means that maintenance is reduced as surface treatments such as stains and paints last 3 to 5 times longer.

Finally, what happens to Accoya wood at end of life? Because only carbon, hydrogen and oxygen, have been added in the acetylation process, chemicals which are all present naturally in timber before modification, Accoya wood can be treated in exactly the same manner as any unmodified wood and so it is 100% recyclable.

To find out about Accoya please visit their website.