Accoya wood is one of those inspirational materials that one stumbles upon and then constantly looks for opportunities to use it. The first time I encountered Accoya was at an in-office CPD seminar arranged by their UK rep, at least 12 years ago. I remember the hour long session vividly. Being a lover of all things scientific the technology engaged me. Accoya wood is carefully selected pine, (Pinus Radiata I seem to recall), that is then pressure treated with acetic acid (vinegar). Somehow or other, the treatment acts at a cellular level whereby cells can not shrink or expand with changing moisture content. As a result the treated timber is absolutely dimensionally stable in all external conditions.
The CPD slideshow included images of a water tank at Accoya's treatment plant where a sliding sash window was submerged. According to the rep, the window was periodically removed from the tank and left to dry, so in either a saturated or unsaturated state, it could be demonstrated that the window remained dimensionally stable and always operated perfectly.
One thing I do remember at the time was that the case studies presented had images of external cladding with loads of knots. I expressed my concern as to the appearance and the rep admitted that this was an issue that many architects had raised and that their timber selection process was under review.
Many years later my first Accoya opportunity arose, a new build steel/timber framed contemporary house in Woodstock, Oxfordshire. We proposed the material as a soffit lining above the main entrance. By now the whole 'knot' issue had been resolved, and all Accoya was supplied knot free.
The contractor working on this project had by now also become a fan. The contractor became a new client and we worked on another project with them that resulted in proper Accoya mania. External walls and roof, all Accoya clad.
More recently we persuaded a private school in Oxford to use Accoya for external wall cladding, brise soleil, and external sliding louvres at an extension to their sixth form centre.
Best left unfinished so as to weather naturally, Accoya is our preferred material for external timber cladding. It carries a hefty price tag, equivalent to seasoned oak or cedar, but performs so well that it is hard to avoid.
AJP Architects Ltd